CN118743081A - System and method for controlled battery heating - Google Patents

Abstract

A system and method for heating a battery, which may be performed alone or in combination with charging or discharging the battery. In some embodiments, heating involves applying an alternating current waveform to the battery, which may be sinusoidal. In some embodiments, the heating signal is applied at a frequency and/or current having little or no net charge to the battery.

Description

System and method for controlled battery heating

CROSS-REFERENCE TO RELATED APPLICATIONS

This Patent Cooperation Treaty (PCT) application is related to U.S. Provisional Patent Application No. 63/313,147, filed on February 23, 2022, entitled “Systems and Methods for Controlled Battery Heating Sourcing Current To and From the Battery,” and U.S. Provisional Patent Application No. 63/331,633, filed on April 15, 2022, entitled “Systems and Methods for Controlled Battery Heating,” and claims priority from the U.S. Provisional Patent Applications under 35 U.S.C. §119(e), the entire contents of each of which are incorporated herein by reference for all purposes.

The present application also relates to a continuation-in-part of U.S. patent application Ser. No. 17/699,016, filed on Mar. 18, 2022, entitled “System and Methods of Controlled Battery Heating Sourcing Current To and From The Battery and Discharge Signal Conditioning From the Same,” which claims, under 35 U.S.C. §119(e), U.S. Provisional Patent Application Ser. No. 63/163,011, filed on Mar. 18, 2021, entitled “Powering A Load from a Battery Discharging with Harmonic Components,” and U.S. Provisional Patent Application Ser. No. 63/163,011, filed on Feb. 23, 2022, entitled “System and Methods for Controlled Battery Heating Sourcing Current To and From the Battery and Discharge Signal Conditioning From the Same.” The present invention claims priority benefit of U.S. Provisional Patent Application No. 63/313,147 filed with the same authority as incorporated herein by reference in its entirety.

Technical Field

Embodiments of the present invention generally relate to systems and methods for heating and/or charging or discharging a battery.

Background Art

Countless different types of electric devices, such as power tools, mobile computing and communication devices, portable electronic devices, and all kinds of electric vehicles including scooters and bicycles, use rechargeable batteries as a source of operating power. Rechargeable batteries are limited by limited battery capacity and must be recharged after exhaustion. Recharging the battery may be inconvenient because the electric device must usually be stationary during the time required to recharge the battery. Depending on the size of the battery, recharging may take several hours. In addition, battery charging is often accompanied by degradation of battery performance. Therefore, a lot of work has been invested in developing battery charging technology to shorten the time required to recharge the battery, improve battery performance, reduce battery degradation due to charging, etc.

Various battery types, including lithium-based batteries, are generally not able to be charged at low temperatures without damaging the cells. In some cases, particularly in liquid electrolyte batteries, the electrolyte may freeze. Attempting to charge when the electrolyte is frozen or otherwise when the battery temperature is below a certain threshold may damage the battery through electrode plating. This can obviously be a problem in many use cases where the battery is discharged but the temperature is too low for conventional charging.

It is with these observations, as well as other factors, that various aspects of the present disclosure were conceived.

Summary of the invention

One aspect of the present disclosure relates to a system for heating a battery, the system comprising a processor in communication with a circuit, wherein the processor is configured to execute instructions for heating the battery by controlling the circuit to alternate between supplying current to the battery and sinking current from the battery, and the combination of supplying current to the battery and sinking current from the battery heats the battery.

Another aspect of the present disclosure relates to a battery-powered system, the battery-powered system including a battery and a processor in operable communication with a charging circuit of the battery, the processor operably coupled to the charging circuit to control at least one harmonic component of a discharge signal from the battery. The system may further include a signal conditioning element positioned between the battery and a load system, the signal conditioning element receiving the discharge signal from the battery and providing a DC signal to the load system.

Another aspect of the present disclosure relates to a method for charging a battery, the method comprising, in response to obtaining information indicating whether the battery is rechargeable, alternating between providing current to the battery and absorbing current from the battery to heat the battery. The method may further include receiving a temperature measurement of the battery, the temperature measurement providing information indicating whether the battery is rechargeable. In one possible example, obtaining a response from the battery based on the application of a signal with known harmonics provides information indicating whether the battery is rechargeable. In another possible example, the response is an impedance response, and the information is a correlation of the battery temperature with the impedance response. In various embodiments, an impedance or admittance response is discussed, and it should be recognized that the term impedance response encompasses its inverse admittance response, and the term admittance or admittance response similarly encompasses its inverse impedance or impedance response.

Another aspect of the present disclosure relates to a method of charging a battery, the method comprising, in response to obtaining information indicating whether the battery is receptive to charging, applying a harmonically tuned signal to the battery, wherein the harmonically tuned signal is composed of at least one harmonic associated with a conductance response and a reactance response to heat the battery. The method may further involve receiving a temperature measurement of the battery, the temperature measurement providing information indicating whether the battery is rechargeable. Another example may involve obtaining a response from the battery based on the application of a signal having known harmonics, thereby providing information indicating whether the battery is rechargeable. In one example, the response is an impedance response, and the information is a correlation of the battery temperature with the impedance response. At least one harmonic may be a higher frequency than the kinetics and diffusion processes of the battery. If the signal is composed of multiple harmonics, the set of harmonics may be a higher frequency than the kinetics and diffusion processes of the battery.

Another aspect of the present disclosure relates to a method of heating a battery, the method comprising generating a repetitive signal to apply to the battery, the repetitive signal comprising a first portion and a second portion within a cycle, the first portion defining a sinusoidally shaped leading edge that rises to a main portion, the main portion terminating in a falling edge, the first portion defining a first percentage of the cycle, the second portion comprising an alternating current following the falling edge of the first portion, the second portion defining a second percentage of the cycle, wherein the first percentage and the second percentage constitute the cycle.

Another aspect of the present disclosure relates to a method for charging a battery, the method comprising applying a detection signal to the battery, the detection signal comprising a plurality of harmonics, the plurality of harmonics comprising at least a first harmonic and a second harmonic. The system/method further relates to: obtaining a voltage response and a current response at the battery based on the detection signal; and generating an impedance spectrum comprising a first impedance of at least a first harmonic and a second impedance of a second harmonic based on the voltage response and the current response, the first impedance being less than the second impedance; and generating a charging signal to apply to the battery, the charging signal comprising a sinusoidally shaped leading edge of the frequency of the first harmonic.

Another aspect of the present disclosure relates to a method of heating a battery, the method comprising applying an alternating current to the battery to heat the battery, wherein the alternating current is at a frequency greater than a frequency at an inflection point of a conductance response or less than a frequency at an inflection point of a susceptance response. More specifically, the frequency is greater than a frequency at an inflection point of a conductance response and less than a frequency at an inflection point of a susceptance response.

Yet another aspect of the present disclosure relates to a method of heating a battery, the method comprising applying an alternating current to the battery to heat the battery, the alternating current being at a frequency at which a conductance response of the battery is decreasing and a susceptance response of the battery is increasing.

These and other features of the present disclosure are discussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

From the following description of the embodiments of those inventive concepts, the various objects, features and advantages of the present disclosure set forth herein will be apparent, as shown in the accompanying drawings. It should be noted that the drawings are not necessarily drawn to scale or include every detail, and may represent various features of the embodiments, with emphasis on illustrating the principles and other aspects of the inventive concepts. Also, in the drawings, the same reference numerals may refer to the same or similar parts throughout the different views. It is intended that the embodiments and drawings disclosed herein be considered illustrative rather than restrictive.

FIG. 1 is a circuit diagram of a battery heating and charging system according to one embodiment, further illustrating a charging path and a load path starting from a power source.

2 is a circuit diagram of the battery heating and charging system of FIG. 1 , further illustrating a discharge path from the battery and a load path from a power rail including a power source.

3 is a circuit diagram of the battery heating and charging system of FIGS. 1 and 2 , further illustrating a charging path and a load path starting from a power rail (eg, a capacitor on the power rail) where the power source is not supplying energy (eg, current).

4 is a signal diagram of a first example heating signal including symmetrically shaped charging current portions and discharging current portions according to one embodiment.

5 is a signal diagram of a second example of a heating signal including asymmetrically shaped charging and discharging current portions according to one embodiment.

6 is a signal diagram of a third example of a heating signal including charging current portions and discharging current portions of different shapes according to one embodiment.

FIG. 7 is an example of a characteristic curve for heating a battery until the battery temperature will permit charging.

FIG. 8 is a flow chart of a method of heating a battery according to one embodiment.

9A is a signal diagram of a first combined charging and heating signal, according to one embodiment.

9B is a signal diagram of a second combined charging and heating signal, according to one embodiment.

10A is a signal diagram of a charging signal including a 0A rest period, according to one embodiment.

10B is a signal diagram of a charging signal including a rest period with non-zero current, according to one embodiment.

FIG. 11 is a flow chart of a method for shaping a charging signal according to an embodiment.

FIG. 12 is a flow chart of a method of identifying a charging current level that takes battery temperature into account, according to one embodiment.

13 is a diagram of a system including signal conditioning elements for converting an unconventional, non-DC current from a battery into a signal for power conversion or consumption by a load that otherwise typically requires a DC signal.

14A is a graph of the conductance response of a lithium-ion battery, which is used to establish the frequency of a heating signal, in one embodiment.

14B is a graph of the susceptance response of a lithium-ion battery, which is used to establish the frequency of the heating signal, in one embodiment.

FIG. 15 is a diagram illustrating an example of a computing system that can be used to implement embodiments of the present disclosure.

DETAILED DESCRIPTION

Disclosed herein are systems, circuits, and methods for heating and charging (recharging) a battery. The terms charging and recharging are used synonymously herein. Various aspects of the present disclosure may provide several advantages over conventional charging, either individually or in combination. For example, the charging techniques described herein may allow the battery to be heated to a level sufficient for charging. In some cases, the battery temperature is monitored, and when the battery temperature is below a threshold, the system initiates a heating sequence before charging, and when the battery is sufficiently heated, transitions to a charging sequence. Temperature thresholds may be customized for various battery chemistries. In one example, the temperature thresholds for heating, a combination of heating and charging, and charging may depend on or be related to the freezing temperature of a liquid electrolyte, but various possible temperature parameters and thresholds are contemplated. In addition, some battery chemistries (such as those in solid-state batteries) do not have liquid electrolytes, but are still affected by temperature, so that charging at too low a temperature may damage the battery. The system may also involve circuit elements of a charging technique that allows for a reduced rate of anode damage, which circuit elements can control the heat generated by the battery by generating heat when charging has begun or minimizing heat generation above a certain level, which can have a number of subsequent effects, such as reducing electrode and other battery damage, reducing the risk of fire or short circuit, etc.

When discharging the battery, whether for heating or powering a load, aspects of the present disclosure further relate to a discharge signal conditioning element positioned between the battery and the load or integrated within the load. Conventionally, the battery discharges to the load via a DC signal, or the DC signal from the battery is converted to an AC signal, such as by an inverter, to power an AC motor. However, whether for heating or otherwise, aspects of the present disclosure relate to unconventional non-DC discharge signals. The discharge signal conditioning element is used to condition an unconventional discharge signal suitable for a load or an element that uses energy from a battery to power a load.

In one example, various embodiments discussed herein manage energy in and out of a battery by generating a controllably shaped charge or discharge signal. The shape may be tuned based on the impedance effect of the battery on various harmonics. In some examples, during heating, the shape, which may include harmonic aspects when charging or discharging, is tailored to heat the battery and minimize damage to the battery or achieve other effects. In some examples, during charging, the shape or content of the charging signal (which may also include harmonic aspects) is optimized for charging. During heating, the system may select harmonic attributes associated with relatively high impedance compared to charging in which the system may control the charging signal to include harmonic attributes associated with relatively low impedance.

The system may further use a model of one or more components of the charge/discharge signal shaping circuit. Conventional charging techniques (DC techniques) such as constant current or constant voltage do not involve charging signal shaping, and therefore the control is relatively simple and does not require the charging and discharging signal shaping techniques discussed herein. The model can be used to confirm and/or adjust the control of the signals generated into and out of the battery, and the combination that may exist during heating. In some examples, various aspects of the shape and/or content of the charging signal may correspond to one (or more) harmonics associated with optimal energy transfer to the battery, but the purpose of the system is to be able to effectively generate any arbitrarily shaped charging signal and apply it to the battery, as well as other goals. In other examples, particularly around battery heating that may occur before charging, it involves shaping and/or defining a signal intended to cause heating and minimize or eliminate charging during the time when the battery is heated in preparation for charging (or discharging). However, the control shape or signal content, the shape or signal content can be any arbitrary shape defined by the control and in some examples includes defined harmonic content.

In one possible implementation, a feed-forward technique utilizing a model to determine a control signal for defining a charge/discharge signal may provide several advantages, including accuracy and speed of signal adjustment. In addition, the arrangement may operate with fewer components than other methods, thereby reducing cost and using less printed circuit board footprint, among other advantages. Whether or not a model is used, the method may further include adjusting a signal from one of the heating to charging when the battery reaches an appropriate temperature, followed by an adjustment of the signal when charging the battery.

Whether or not a model is used, aspects of the system may further include feedback on temperature and other battery parameters both during the heating phase and during the transition to and through the charging phase. Feedback alone or in combination with a model may allow the system to adjust for component drift, adjust for the impact of temperature or other effects on circuit components, adjust for changes in the battery, and periodically provide additional data to the system and/or model to change its output, among other operations. In addition, the system may use battery temperature to select between heating or charging, and in some examples, transition between the heating phase to a phase in which charging is optimized without heating, which may include transition phases for both heating and charging.

The term "battery" in this technology and herein can be used in various ways, and can refer to individual cells having anodes and cathodes separated by solid or liquid electrolytes, as well as collections of such cells connected in various arrangements. A battery or battery cell is a form of electrochemical device. A battery typically includes a repeating unit of a counter charge source and an electrode layer separated by an ion-conductive barrier, which is often a liquid or polymer film saturated with an electrolyte. These layers are made thin so that multiple units can occupy the volume of the battery, thereby increasing the available power of the battery per stacked unit. Although many of the examples discussed herein are applicable to batteries, it should be understood that the described systems and methods can be applied to many different types of batteries, from individual cells to batteries involving possible different interconnections of cells (e.g., cells coupled in parallel, coupled in series, and coupled in parallel and in series). For example, the systems and methods discussed herein can be applied to a battery pack comprising many cells, which are arranged to provide a defined group voltage, output current, and/or capacity. Furthermore, the embodiments discussed herein can be applied to different types of electrochemical devices, such as various different types of lithium batteries, including but not limited to lithium metal and lithium ion batteries, lead acid batteries, various types of nickel batteries, and solid-state batteries, to name a few. The various embodiments discussed herein can also be applied to different structural battery arrangements, such as button or "coin" type batteries, cylindrical cells, pouch cells, and prismatic cells.

Figures 1 to 3 show a battery heating and charging circuit topology according to an embodiment of the present disclosure. The arrows shown in the figures define the current flow paths during different operating states of the system. In Figure 1, the system is shown in a configuration that supplies current to the battery (charging) and powers the load. In Figure 2, the system is shown in a configuration that draws current from the battery (discharging or absorbing), a discharge path to the capacitor on the rail, and powers the load when the power is on (connected to the rail). In Figure 3, the system is shown in a configuration that draws current from the battery to the capacitor on the rail and powers the load when the power is off (not connected to the rail). In both Figures 2 and 3, there is also an arrow showing the "blip" path to the lower second transistor, which briefly turns on the discharge current path.

FIG. 1 , as well as FIGS. 2 and 3 , are schematic diagrams showing an example charging signal generator arrangement 100 for heating, charging, and/or discharging a battery 104. The generator includes a processing unit or more generally a control unit 106, which may include a controller, such as a microcontroller, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a microprocessor, a combination thereof, or other processing arrangement, which may communicate with a signal generator 108, which generates control for generating a charging signal from a charging signal shaping circuit 110. The controller may communicate with a model, which may be part of the generator, to generate control instructions to the charging signal shaping circuit. The control unit including the controller and the model (if present) may be an integrated unit. The system may also receive feedback including battery measurements from a battery measurement unit 116, such as current and/or voltage measurements at the battery terminals of the battery 104 in the presence of a signal (heating, charging, and/or discharging), and the battery measurements may be used to obtain impedance measurements and/or affect heating or charging control. Typically, the generator may also include or be operably coupled to a power source 118, which may be a voltage source or a current source. In one embodiment, the power source 118 is a direct current (DC) current or voltage source, but alternating current (AC) sources are also contemplated. In various alternatives, the power source 118 may include a DC source that provides a unidirectional current, an AC source that provides a bidirectional current, or a power source that provides a ripple current (e.g., an AC signal with a DC bias to cause the current to be unidirectional). Typically, the power source 118 supplies charging energy, such as a current, which may be shaped or otherwise defined by the control unit 106 and the circuit 110 to generate a controllably shaped charging signal to heat, charge, and/or discharge the battery 104. In one example, the controller 106 may provide one or more inputs to the signal generator 108, which controls a switch to generate a pulse to the circuit 110, which may also be referred to as a filter, which generates a shaped signal at the battery.

In some examples, the signal shaping circuit 110 may change the energy from the power source 118 to produce a signal shaped based on the conditions at the battery 104, such as a signal corresponding at least in part to one or more harmonics based on the impedance when the signal including the harmonics or harmonic attributes is applied to the battery 104. In the example of FIG. 1, in addition, the circuit 100 may include a battery measurement unit 116 connected to the battery 104 to measure the cell voltage and/or charging current, as well as other battery attributes such as temperature, and measure, calculate, or otherwise obtain the impedance of the battery 104 based on the aforementioned measurements. In one example, the battery characteristics may be measured based on the signals entering and exiting the battery. In another example, the battery cell characteristics may be measured as part of a routine of applying a signal with a varying frequency attribute to produce a range of battery cell characteristic values associated with different frequency attributes in order to characterize the battery, which may be done before, during, during, and periodically during heating, charging, or discharging, and may be used in combination with lookup techniques and other techniques. The battery characteristics may vary based on many physical and chemical characteristics of the battery, including the state of charge and/or temperature of the battery. Thus, battery measurement circuit 116 may be controlled by controller 106 to determine various battery characteristic values of battery 104 during heating, recharging of the battery, and/or powering a load, as well as at other times, and provide the measured battery characteristic values to controller 106 or other portions of generator 100.

During charging, the controller 106 may generate an expected charging signal for efficient charging of the battery 104. For example, the controller 106 may generate or select a charging signal having properties corresponding to harmonics associated with an optimal impedance for energy transfer (which may be an impedance range) using the determined impedance of the battery 104 or a signal definition characterized based on understanding the impedance effect of the signal on the battery, which may be associated with the minimum impedance value of the battery 104. Thus, the controller 106 may execute a charging signal algorithm that outputs a charging signal shape based on the measured, characterized, and/or estimated charging conditions of the battery 104. In general, the signal generator controls the switch to generate a pulse train at the node 136, which is converted by the circuit 110 into a charging signal shape. Similarly, during heating, the battery may be characterized based on temperature to understand the impedance effect of the charging or discharging signal on the battery and the signal controlled based on the impedance effect. Here, the node 136 may be similarly controlled, but so that a current with a defined impedance property is both supplied to and absorbed from the battery by means of the circuit 110. It should be appreciated that heating may also involve a transition from current into or out of the battery, characterized by optimizing heating, minimizing or eliminating plating, and minimizing any energy storage in the battery during the heating sequence. The signal generator 108 may generate one or more control signals based on a heating or charging signal algorithm, and provide those control signals to the signal shaping unit 110. The control signal may shape or otherwise define the signal into or out of the battery to approximate a shaped charging signal determined, selected, or otherwise obtained by the controller 106, as well as other functions. The charging signal shaping circuit 110 may further filter out any undesired frequency attributes from the signal. In some examples, the shaped charging signal may be any arbitrarily shaped signal such that, whether heating, charging, or discharging, the signal is not a constant DC signal and does not conform to a conventional repetitive charging signal, such as a repetitive square wave or triangle wave charging signal.

According to one embodiment, the circuits of FIGS. 1 to 3 include switching elements 112, 114, which may be considered part of circuit 110, to generate an initial sequence of controlled pulses at node 136, which are then converted by filter 110 into a shaped signal to generate a signal applied to or from the battery. The switching elements may also be used to generate a discharge signal from the battery by pulses similarly generated at node 136 in the absence of a charging current on rail 120.

As introduced, the circuit 100 may include one or more components to shape a signal that intentionally heats the battery through a coordinated combination of charging and discharging at the battery 104. The circuit 100 may include a first switching element (e.g., a transistor 112) and a second switching element (e.g., a transistor 114), wherein the first switching element is connected to the power rail, thereby connecting to the power source 118 during charging and coupling to the capacitor 122 on the rail during discharging. The capacitor may have various functions, including discharge signal conditioning as discussed in more detail below. The first transistor 112 may receive an input signal such as a pulse width modulation (PWM) control signal 130 to operate the first transistor 112 as a switching device or component. In general, the first transistor 112 may be any type of transistor, such as a FET, or more specifically, a MOSFET, a GaN FET, a silicon carbide-based FET, or any type of controllable switching element. For example, the first transistor 112 may be a FET, wherein the drain node is connected to the first inductor 140, the source is connected to the rail, and the gate receives the control signal 130 from the signal generator 110. In various embodiments, circuit 110 also includes inductor 140, but may also have a variety of other possible inductive elements. When operating in a bidirectional manner for both charging and discharging and as described in more detail below, circuit 110, and in particular the combination of inductors 142, 140 and capacitor 148, may be considered a step-up topology when controlling current from the battery during the discharge portion of heating or more generally during sinking current into a load during normal operation.

When heating, the system can be operated to supply current to the battery (commonly referred to as charging, but it is recognized that during heating, the system optimizes the source current for heating rather than charging), and to sink current from the battery (discharging, similarly recognizing that during heating, the system optimizes the current from the battery for heating rather than powering the load). The system can control the heating sequence to quickly transition from supplying current to the battery and sinking current from the battery. To supply current (charging), the circuit controller 106 can provide a control signal 130 to control the operation of the first transistor 112 as a switch, which when closed connects the first inductor 140 to the rail 120 so that current from the power supply (and/or from the capacitor 122) flows through the first inductor 140, and the second inductor 142 (if present), to the battery. The second transistor 114 can receive the second input signal 132 and can also be connected to the drain of the first transistor 112 at a node 136. In a charging situation, and in some examples, the second input signal 132 may be a PWM signal that is the inverse of the first control signal 130 to the first transistor 112 such that switching is coordinated by turning one transistor on and the other off.

One or more inductor values, one or more capacitor values, the time and frequency of actuating the transistor, and other factors may be customized to produce a waveform, particularly one having controlled harmonics to the battery to heat the battery. Referring to the example signals shown in FIGS. 4 to 6 , the signal at node 136 may be a series of pulses between 0 volts and about the rail voltage when current is supplied. The pulses at node 136 may have varying duty cycles and may be produced at varying frequencies. However, in general, the pulses are produced to produce a signal that is the same or nearly the same as the expected current signal into and out of the battery. Thus, for example, a signal such as any of those in FIGS. 4 to 6 will be located at node 138 based on a combination of pulses present at node 136, which are then shaped by filter arrangement 110 into a signal at 138. Depending on the signal, pulses of 10s to 1000s (or longer) may be produced to form the desired charging signal.

The discharge sequence involves initially turning off the upper first transistor 112 and turning on the bottom second transistor 114. The second transistor may be turned on only briefly for a sufficient time to initiate current flow from the battery to the inductors 142, 140. The transistors may be controlled to eliminate or minimize current flowing to ground through the second inductor. When current from the battery is initiated (discharge), the second transistor is turned off and the upper transistor 112 is turned on, with the power supply turned off or on to drive current to the rail capacitor 122 and/or the load 144. Once the current from the battery is initiated, the pulses may be controlled at the node 136 to similarly shape the discharge signal or the discharge portion of the signal. Depending on the type of power required by the load, the system may include some form of power conversion 146. The system may operate with the power supply turned on or off. If it is off, the current is directed to the capacitor and/or the load. If on, the power supply may include functionality that will coordinate the power supplies to maintain the rail voltage, and if the discharge of the current increases the rail voltage above a certain level, it may synchronize the power supplies to maintain the set rail voltage.

In general, during heating, the control system can quickly switch between supplying energy to the battery and absorbing energy from the battery. In addition, the circuit can be operated to shape the current to the battery and/or the current from the battery by controlling the pulse at node 136. Through these features, alone or in various combinations, the battery can be heated to a level sufficient for charging to occur. It should be recognized that various different battery types have different temperature thresholds for including appropriate operations for charging or powering a load. In addition or separately, heating may occur when the battery is charged little or not, where the energy is actually concentrated on heating, thereby minimizing or avoiding plating or other electrode damage, switching to charging and changing the signal to one of optimal charging and switching to not generating excessive heat, using components with multifunctional functions of controlled heating and controlled charging to achieve optimal circuit efficiency, and other benefits.

As introduced, the system may include a first capacitor 122 connected between a power rail and ground. The capacitor may be used to store discharge energy, which may then be used to power a load when charging, either alone or in combination with power from a power source. As discussed in more detail below, the capacitor 122 may also be used to condition the discharge signal before it is further processed by a power conversion element or directly powers a load. In addition, some of the energy required for the charging waveform may be provided by a combination of the power source and the capacitor 122. In some examples, the discharge energy from the battery stored in the capacitor may be returned to the battery during heating and when the system is supplying current to the battery. The circuit may also include a second capacitor 148 connected between the first inductor 140 and the second inductor 142 to ground. The second inductor 142 may be connected to a battery, for example, the anode of the battery 104.

After heating and during charging or powering a load from the battery, the system can generally operate to prevent rapid changes in signals applied to or from the battery 104. In charging operations, the filter can also convert pulses at the input of the filter into a charging signal, as well as filter out any unexpected high-frequency noise from the battery. For example, when the first transistor 112 is closed based on the control signal 130, the first inductor 140 and the second inductor 142 can prevent a rapid increase in the current transmitted to the battery 104. In addition, the inductor 140 or the inductors 140 and 142 alone or in combination with the capacitor 148 can shape the waveform applied to the battery, and the control of the signal applied to the inductor can achieve controlled shaping of the waveform. These components can be similarly used to control the discharge waveform shape. In another example, when the first transistor 112 is closed, the capacitor 148 can store energy from the power supply. When the first transistor 112 is turned off (which may be accompanied by the closing of transistor 114), the capacitor 148 can provide a small amount of current to the battery 104 through the second inductor 142 to resist the immediate drop in current to the battery, and can similarly be used to controllably shape the waveform applied to the battery, particularly to avoid sharp negative transitions during normal charging after heating. The filter circuit also removes other unwanted signals, such as noise, which can include relatively high frequency noise.

It should be understood that more or fewer components may be included in the system. For example, one or more of the components of the filter circuit may be removed or changed as needed to filter or define the signals entering or leaving the battery. Many other types of components and/or configurations of components may also be included or associated with the system.

FIG. 4 to FIG. 6 show alternative possible example heating waveforms. In each case, the controlled waveform transitions between the charging or supply portion 410 (510, 610) to the discharging or absorbing portion 420 (520, 620). At a high level, the heating waveform of FIG. 4 presents a sinusoidal curve, wherein the positive portion of the waveform is the current entering the battery (e.g., the current path to the battery of FIG. 1), and the negative portion of the waveform is the current from the battery (e.g., the current path from the battery to the capacitor on the rail of FIG. 2 or FIG. 3, it should be noted that the current path to ground through the lower transistor is intended only to initiate the discharge current path to the rail capacitor). The shape of the current to or from the battery is controlled by the pulse at node 136. That is, by controlling the frequency, pulse width and/or voltage level of the pulse, the system can shape the waveforms entering and exiting the battery.

The heating waveform of FIG5 has an asymmetric sinusoidal curve in which the current to the battery (the positive-going portion of the waveform) has a larger absolute amplitude than the current from the battery. In some instances, particularly in fully or nearly fully discharged batteries, it may be necessary to add slightly more energy than discharged to avoid over-discharging the battery. The heating waveform of FIG6 has an arbitrarily (albeit controlled) shaped current to the battery compared to the current from the battery. Furthermore, the shape is inconsistent from one arbitrarily shaped input current portion to the next arbitrarily shaped input current portion and from one arbitrarily shaped output current portion to the next output current portion.

The frequency of the transition from supply to absorption, the signal shape of supply and absorption, and various other aspects of the heating sequence may vary. The shape of any part of the signal (whether to or from the battery) may be based on the impedance of the battery to the signal being applied to or from the battery. The signal definition may be preset. The signal definition may also be algorithmic, depending on various battery parameters including SOC, temperature, number of cycles, battery chemistry and configuration, and many other possible attributes. The signal definition may also vary during the heating and charging process. As mentioned herein, impedance and harmonics may affect the charging signal selection or definition. As a general concept, a signal definition associated with a relatively high impedance and associated harmonics may be selected for a heating sequence, where a relatively low impedance and associated harmonics are used for charging or discharging to power a load sequence. It should also be noted that a relatively rapid change between supplying current to the battery and absorbing current from the battery can be used for heating, and once a sufficient temperature is reached, the system transitions from absorbing current (during charging) so that charging will not damage the battery.

In a heating sequence, one or more attributes of the charging and/or discharging portion of the signal may be tailored to a relatively high impedance characteristic, compared to a charging sequence in which tailoring the charging signal to a relatively low impedance characteristic may be optimal. By briefly injecting current into a cell and then briefly pulling current from the cell, heat may be generated without initiating any substantial battery charging. The transition frequency between current entering and exiting the battery may affect optimal heating if the harmonics associated with the transition are relatively high such that the energy is primarily used for heating. Additionally or alternatively, the charging or discharging portion of the waveform may be defined to include harmonic attributes associated with a relatively high impedance. Thus, unlike charging, charging a capacitor during discharge, and/or powering a load during discharge, the current energy entering or leaving the battery may be consumed primarily as heat due to the relatively high impedance (typically resistance).

The battery temperature can be assessed in a variety of ways. In one example, the system can use a temperature sensor at the battery to assess the battery temperature. Various temperature sensors can be employed that are in contact with the battery, in contact with the terminals of the battery, positioned in a housing containing the battery, or in other forms. Various sensor examples include thermistors, thermocouples, infrared sensors, diodes, and transistors, or any of a myriad of different types of temperature sensors.

In another example, a battery response having harmonic or other frequency attributes can be used to detect the internal temperature of the battery, or more generally, the ability of the battery to accept a charge, which may be the same as or slightly different from a measurement of temperature, particularly the external temperature of the battery. The use of a harmonic response can also be used to more uniformly assess the ability of a battery to accept a charge.

In one specific example, the system uses a characterization of the battery's response to various harmonics at different temperatures. Any given battery type or specific battery can be characterized. The characterization can be stored in a lookup table accessible by the processor in a memory by setting a threshold, etc. In this specific example, it should be understood that various different battery chemistries and configurations have different impedance responses at different temperatures. Therefore, for a given battery, the impedance response of a signal with a specific harmonic frequency applied to the battery is different based on temperature. In some examples, temperature detection signals at different discrete frequencies can be used to generate an impedance response, which is then compared with the characterization to evaluate the temperature, or more generally, to evaluate the battery's ability to accept charging, and therefore to evaluate whether heating is required before charging can be initiated. The impedance response can be characterized by the imaginary component, the real component, or both the imaginary component and the real component of the impedance. In some embodiments, the impedance response can be used alone or in combination with the sensed battery temperature measurement value to determine whether the battery should be heated or can be charged. Similarly, other frequency-based responses or impedance derivatives (such as susceptance, admittance, and capacitance) can be used alone or in place of directly sensed temperature measurements to determine whether the system will be configured to heat the battery.

In general, in various embodiments that consider impedance values, the techniques evaluate harmonic values, where the values are associated with a certain impedance, either individually or in combination. Considering the generally inverse relationship, the term "impedance" as used herein may include its inverse admittance, including its components of conductance and susceptance, either individually or in combination.

In another aspect, battery heating may be achieved by controllably charging or discharging the battery, or a combination as discussed above. In this example, the signal (whether a charging signal, a discharging signal, or a signal alternating between charging (supplying current to the battery) and discharging (sucking current from the battery)) is composed of one or more harmonics that are tuned so that the signal optimizes relatively high conductance and relatively high reactance in the battery. Using the charging signal as an example, the optimized combination (or balance) between high conductance and high reactance generates heat in the battery. In this example, the signal is composed of harmonics so that the harmonics can be identified in one or more frequency domain representations (or transforms) of the signal. The tuned signal may also be shaped to reflect various harmonic properties. In a fairly simple example, the signal may also be composed of discrete sinusoids at a particular frequency so that it is both composed of harmonics and shaped in the form of harmonics. In general, even with very high conductance, if the reactance is too low, the magnitude of the signal may be higher than many charging environments can support in order to generate sufficient heat. Similarly, if the conductance is too low, even with high reactance, it may require too much energy to be converted to heat. Therefore, for any starting temperature and battery chemistry, the system selects a charging signal with harmonics that balances high conductance and high reactance.

In one specific example, a given form of battery can be characterized at various temperatures by evaluating signals composed of various combinations of harmonics to identify one or more signals that balance relatively high conductance and relatively high reactance to achieve sufficient heating. Characterization can also determine when the heating signal is applied to reach a state sufficient to begin heating. The balance can further consider properties that minimize the energy used for actual charging, so the energy is actually focused on heating. The same techniques can be applied to generate discharge signal harmonics that can be the same or different from the charging signal at various temperatures.

The harmonic frequency can generally be a relatively higher frequency than the kinetic and diffusion processes in any given battery that the signal is optimized to heat. In general, a frequency that is faster than the kinetic response of the electrochemical process is selected so that the voltage and current magnitudes do not adversely affect the electrodes or interfaces of the battery when heating occurs. Therefore, when heating, a relatively high voltage signal (e.g., 6V when a maximum value of about 4V is generally specified) will be used, which will generally lead to plating, but because the signal is composed of harmonics or harmonic spectra that are faster than the kinetics, the relatively high voltage will not lead to plating. Nevertheless, in many examples, a signal that falls within a relatively low prescribed charge (or discharge) voltage level is selected. In addition, using the various heating techniques described herein, in some examples, the system is optimized to heat without transferring any net charge. In such examples, the system controls the signal to charge and discharge with a relatively uniform total energy so that the signals cancel each other, thereby resolving any differences in the energy conversion efficiency differences between the charging portion and the discharging portion at any given temperature.

Figure 7 is an example of a characteristic curve for heating a battery until the battery temperature will allow charging. In this example, the initial battery temperature is -20°C and the SOC is at 10%. The battery is heated until it reaches about -15°C, at which point charging of this battery can begin. It can be seen that the SOC remains at about 10% as the battery warms up about 5°C before charging begins. It can also be seen that the temperature of the battery continues to rise until the SOC reaches 100%.

In many conventional battery powered systems, the system relies on a DC discharge current from the battery to provide power to a certain load. The battery may be a single cell or a small number of cells, such as in a power tool, a vacuum cleaner, a portable speaker system, etc., or may be a large interconnected group of cells, such as that found in a certain type of electric vehicle. The arrangement and type of cells will generally depend at least in part on the specified capacity of the system in which the battery operates, the required discharge current of the system's load, and other factors. In any case, conventional batteries provide a DC discharge current when powering a load. When an AC signal is required to drive a load (e.g., an AC motor), a converter such as converter 146 is used to convert the DC output of the battery into an AC signal required by the load.

For battery heating and controlling charging based on heating, and for defining the shape of a harmonically tuned charging signal during or after heating or otherwise, aspects of the present disclosure relate to unique battery charging and heating sequences based on the starting temperature of the battery and the expected temperature change during charging. Aspects of the present disclosure further relate to techniques for shaping the charging signal to achieve optimal charging (whether heating, charging, or some combination of heating and charging). The charging signal may have a harmonically shaped leading edge. In other words, the leading edge of the charging signal may be defined by the frequency of a sinusoid and may have a corresponding shape. Aspects of the present disclosure further relate to methods for determining a maximum charging current that can be applied based on the current state of the battery and taking into account battery heating and/or battery temperature, either alone or in combination with either or both of a heating sequence and a shaped charging signal.

In one aspect, the charging system is configured to evaluate the battery temperature and determine the charging sequence based on the battery temperature. As discussed above, in some cases, the temperature of the battery may be at or below a certain threshold at which charging may damage the battery or may not be effective at all. In this case, the system may generate a signal to warm the battery. As mentioned above, various possible warming signals are possible. When the battery temperature rises above a threshold, the system may start charging the battery while continuing to warm the battery. Finally, above a second threshold, the system may stop warming and switch to a signal that is intended only to charge the battery. However, it should be recognized that charging the battery tends to heat the battery. One benefit of a harmonically tuned charging signal is that it optimizes the use of energy for charging, so less heating may occur compared to various conventional charging techniques. Thus, during charging, more current may be supplied than conventional systems because the charging technique generates less heat, among other advantages.

Turning now to a specific method of heating a battery, FIG8 is a flow chart showing one possible example of a method of heating a battery, and FIG9A and FIG9B show possible examples of combined charging and heating signals. The magnitude of the current used for the signals of FIG9A and FIG9B will depend on the cell capacity and the external temperature. For example, for some cell types, for a 3Ah or 4Ah cell, the peak current will be about 6A to 12A. In some cases, higher magnitudes for heating are possible and will heat the battery faster (compared to lower magnitude signals). Higher magnitudes than those specified for charging are possible, and such magnitudes can potentially be relatively large, due to the fact that a heating frequency that does not affect the electrochemical process can be selected, for example, a signal at a current of 60App or greater.

Referring to FIG. 8 , first, the charging system obtains the battery temperature (operation 800). The battery temperature may be obtained in a variety of ways. As discussed above, the battery temperature may be obtained from one or more temperature sensors located in or at the battery (or battery pack, in which case more than one temperature sensor may be used). In addition to the battery temperature, the system may also obtain the ambient temperature (environmental). It should be appreciated that the battery temperature may also be calculated from other information in addition to the sensed battery temperature.

Depending on the battery type, the system may identify a first temperature T1 at or below which the battery should be heated prior to charging, a temperature range that may be between the relatively lower first temperature T1 and a second relatively higher upper temperature T2 (between the first temperature and the upper temperature, the system may begin charging and the system may also continue heating), and an upper temperature T2 above which heating is no longer required and the system may charge without continued purposeful heating. For purposes of example, the method and system are discussed with reference to three effective temperature zones at or below T1, between T1 and T2, and at or above T2; however, it should be recognized that the method and system may include more or fewer zones and modify the various heating and charging actions accordingly. For example, the intermediate zone may be split into sub-zones where the system transitions between effectively doing more heating to effectively doing less heating, and from effectively doing less charging to effectively doing more charging, as the system as a whole transitions from a first state where the system is only heating to a third state where the system is only charging. Regardless of the sub-regions into which the intermediate zones or states are split, in the intermediate stages the system may charge at a smaller rate than in the final stages in which the battery has risen to a temperature at which charging can continue without additional heating. Regardless, in one particular example, the system determines from the obtained temperature T of the battery which mode to initiate, i.e., heating, mixed heating and charging, or charging (operation 802).

In the first mode (operation 904), when the temperature is too low to charge (e.g., when T is at or below T1), the system accesses a signal for heating only. Examples of such signals are discussed with reference to FIGS. 4 to 6 as examples, and examples of such signals may be provided by, for example, the circuits shown in FIGS. 1 to 3 . In one particular embodiment, the heating signal is a sinusoidal current waveform, as generally shown in FIG. 4 . The current waveform is centered around zero current, with alternating sinusoidal positive currents 410 and negative currents 420. The frequency of the sinusoid may be selected based on the battery type and through battery characterization and testing. When the temperature is deemed too low to charge without potentially damaging the cell, one goal of an alternating heating waveform in the form of a sinusoidal curve or other shape centered around zero current is to first heat the battery without producing any meaningful net charge and other matters discussed above.

The method is discussed from the perspective of starting with a first mode (operation 804), checking the temperature, and then proceeding to a second mode and then to a third mode based on the battery temperature. It should be appreciated that the method may start first in the second or third mode depending on the starting temperature. In addition, in some arrangements, the heating sequence may be initiated for a period of time, as opposed to when the battery reaches a certain temperature (e.g., T1 or T2). Thus, for example, if the initial temperature is below T1, the system may initiate a heating sequence for a period of time and then transition to hybrid mode two discussed below, or simply bypass the hybrid mode and move to full charge mode three in an embodiment without an intermediate mode or in a case where the timing should be set to not involve an intermediate mode. It should be noted that other thresholds other than battery temperature (e.g., time or current applied, time at ambient temperature, modeling, and combinations thereof) are also possible. Similarly, while the method is discussed primarily with respect to reaching different threshold temperatures T1 and T2, the system may function when the temperature is reached, when the temperature reaches a range near the temperature, and in other cases.

It should be appreciated that other heating signals may also be used in the first mode. In the case where the charging sequence is first initiated when the temperature is below T1, and therefore the heating mode is first initiated, depending on the temperature, a transition may be made from a sinusoid centered at zero to a sinusoid with some positive DC offset, such that some charging is initiated or started at the sinusoid with some positive DC offset or other greater positive charge energy, such as in the signal of FIG. 5 . Subsequently, when temperature T1 is reached and the battery heats up above T1 or even above a second temperature at which the system transitions to a full charging sequence, the signal may transition to the second mode discussed below.

Continuing with the example of FIG. 8 , when temperature T1 is reached, the system may transition to a second mode. In the second mode, when the battery temperature falls within a certain range (e.g., T between temperature T1 and temperature T2), the system may use a hybrid charging signal, an example of which is shown in FIGS. 9A and 9B . The hybrid charging signal may include charging portions 902, 904 and heating portions 906, 908. The example shows a repeating pattern of a charging portion followed by a heating portion. However, the hybrid signal may include any sequence of charging portions and heating portions. For example, the hybrid charging signal may include a sequence of a certain number of charging portions (e.g., 902 or 904) followed by a heating portion (e.g., 906 or 908), and then a subsequent sequence of heating portions. In this example, each charging portion will begin where the current charging portion ends. Similarly, the duration of the charging portion and the heating portion may vary. For example, near temperature T1, the heating portion may be relatively longer than the charging portion than when near temperature T2, at which the charging portion may be relatively longer than the heating portion (or a series of charging portions (which may include intervening rest periods) may occur before the heating portion), or some heating portions may be replaced with rest periods as discussed below and elsewhere herein. In the examples of FIGS. 9A and 9B , the rest period would involve a transition 918 (920) from a charging portion 914 (916) to a rest period with no charging or discharging current (or substantially no charging or discharging current) occurring at the location where the heating portion 906 or 908 is shown, and then a transition to another charging portion 902 or 904. Similarly, the mixed signal may include less relative charge energy near temperature T1 and more relative charge energy near temperature T2. Similarly, the mixed signal may change dynamically or programmatically as the temperature increases between temperatures T1 and T2. Similarly, signal definition may be governed by the starting temperature (eg, whether the starting temperature falls somewhere within the range of T1 to T2).

In the example shown, the charging portion 902, 904 of the hybrid charging and heating signal includes a non-abrupt leading edge 910, 912 that is sinusoidally shaped or otherwise more generally shaped, followed by a main body portion 914, 916 that terminates at a falling edge 918, 920. In many examples, the leading edge (e.g., leading edge 910 or 912) may not be an immediate very high frequency edge, such as in a square wave, to avoid injecting high frequency harmonics into the battery when starting the charging portion of the signal. Referring to FIG. 9A, the heating portion 906 falls between the charging portions and is defined by a sinusoidal heating signal centered at approximately zero amperes. Thus, the sinusoid oscillates between positive (charging) current and negative (discharging current). In some examples, the heating signal provides approximately a net zero capacity difference, where the energy during the heating portion of the hybrid signal is primarily used for heating, with little or no net energy for charging or discharging the cell. The heating portion of the charging signal discussed in FIG. 9B has a certain DC offset and will be discussed in more detail below.

In various possible examples, the frequency range of the sinusoidal heating portion of the mixed signal or just the heating signal (discussed previously) may be 1 KHz to 100 KHz. Depending on the cell and specific conditions, the frequency range may also drop below 1 KHz, such as in the range of 100 Hz to 1 KHz. Similarly, in some cases, frequencies above 100 KHz are possible. In one specific example of a 3000 mAh lithium-ion rechargeable cell, where the specified maximum discharge current is 35 A and the specified current is 4 A at 4.2 V for conventional CCCV charging, the heating sinusoid may be 10 KHz and cycle between -10 A and 10 A (in the case of this cell, the temperature T1 may be about -10°C and the temperature of the cell may reach 5°C at T2). The heating as described in this example and other examples herein causes the maximum possible internal heat generated by the contributions of both resistance and susceptance mechanisms. The susceptance caused by the curled electrode generates a magnetic field, which is absorbed by the magnetic elements in the cathode, allowing the magnetic elements to participate in heat generation in parallel with the l ² R heating performed by the current collector. It should be recognized that this relatively high current is usually specified at a relatively low temperature. For example, for the same type of battery cell, the conventional charge (if allowed) will be about 2A. However, as mentioned above, the energy of the heating portion of the signal is mainly used for heating, allowing higher current than when charging only. The frequency of the heating signal and the positive and negative current values will vary depending on the type of battery, the capabilities of the charging circuit system, the capabilities of the power supply, and other factors. Although the heating sinusoidal signal can be symmetrically positive and negative (for example, cycling between +10A and -10A), it is also possible to have an asymmetrical signal. The sinusoidal curve can also be centered at a positive DC offset (for example, as shown in Figure 9B) so that there is some net charge during the heating portion, or transition from a zero-centered sinusoidal curve to a non-zero positive offset sinusoidal curve as the battery heats up through the temperature zone between T1 and T2. Mode two can also be operated within a set time period, or modes one and two can be operated sequentially and in combination within a set time period, where the transition from the first mode to the second mode is based on time. In addition to time and temperature, other thresholds may be used to transition between signals, such as ambient temperature, net current to the battery, using other measurements such as voltage as a proxy for temperature, etc.

In the third mode (operation 808), when the battery temperature T is at a temperature T2 sufficient for charging without additional heating, the system transitions to the charging sequence. In various aspects, and referring first to FIG. 10A, the charging signal 1000 includes a shaped leading edge 1010, a main portion 1020, and a rest portion 1030. In a mixed signal or charging signal, the shape of the leading edge can be a sinusoidal shape at a frequency selected based on a relatively low impedance harmonic frequency. The sinusoidal leading edge is followed by a relatively stable charging current (e.g., the main portion 1020), which terminates at a falling edge. Unlike a mixed signal, the falling edge is not followed by a sinusoidal heating portion, but is actually followed by a rest period 1030. The rest period can be zero current, or can be some non-zero DC current that is less than the current of the main portion (see, e.g., FIG. 10B). Depending on the type of cell, the peak current of the main portion can be in the range of 10A to 60A, and the rest current is in the range of 0A to 10A. Depending on temperature, cell type, circuit capacity, state of charge, and other factors, the peak current value, rest current value, and other values may vary, as mentioned elsewhere herein. In this example, if the rest current is non-zero, the rest current may be less than the specified charging current when using conventional CCCV charging. For example, if the charging current using CCCV charging is about 4A at 4.2V, the rest current may be 2A or less.

In some examples, a heating signal may be applied to maintain the battery within some operable range. The signal may be applied when the battery temperature drops below a certain temperature threshold, even when the battery is otherwise fully charged. Since the frequency may be selected without a net charge being applied to the battery, heating may be maintained without exceeding an upper charge threshold. Alternatively or in addition, the system may charge and discharge the battery within a small window (e.g., 99%-100%) while also generating a heating signal to maintain the battery temperature. In various examples, when connected to a charger, the system may maintain the battery temperature within a range that is optimal for powering a certain load and avoid the battery from dropping below a certain operable threshold when the battery is in a cold ambient environment that may otherwise cool the battery below or otherwise enter a suboptimal operating temperature range.

With respect to various modes and other approaches, various heating signals, mixed charging and heating signals, and charging signals may be generated using the circuits depicted in FIGS. 1-3 and other approaches.

As mentioned herein, the charging signal or mixed charging and heating signal may include a shaped leading edge, a main body portion, and a rest period, and it should be noted that the rest period may also include a heating sinusoidal superposition. The described charging technique and charging signal are not conventional constant current constant voltage type charging, in which, in essence, a prescribed constant charging current is applied until the battery voltage begins to rise, at which time the charging current is reduced. The charging technique is also not pulse charging, because the charging signal defines a specifically shaped leading edge; in fact, the high frequency harmonic content of square pulses is generally avoided for charging, at least due to the high impedance to the uncontrolled high frequency harmonic content of the square pulse, especially when the pulse is first initiated.

Referring to FIG. 11 , a method of generating the shape of the charging portion of a signal (e.g., a hybrid charging and heating signal or a charging signal) involves obtaining an impedance spectrum of the battery, and selecting frequencies when the impedance is relatively low based on the impedance spectrum, and using the frequencies to define a shaped leading edge of the charging portion of the signal. In one example, the system uses or otherwise references an imaginary impedance (reactance) value. The shaped leading edge and overall signal can be generated using the circuits depicted in FIGS. 1 to 3 , etc.

To obtain an impedance spectrum, in one possible example, the method involves applying a detection signal to the battery (operation 1102). The detection signal may include a harmonic spectrum that can be used by the system to evaluate the impedance of the battery to various harmonics. The detection signal may be a charging signal, or it may be a dedicated signal. The detection signal may be interleaved during charging, or may be run discontinuously at the start of charging, intermittently or periodically during charging, or run in other ways. In one example, the detection signal may be a square wave or square pulse. In a specific example, the detection signal is a square wave centered at zero amperes. In one possible example, the detection signal is a square wave centered at zero amperes, with a +4V (positive) portion and a -4V (negative) portion. Here, the average current is 0A. The duty cycle is 50%. The frequency, duty cycle, current or voltage magnitude or other properties of the detection signal may vary depending on the cell type, device type, temperature, state of charge, and other possible parameters. These parameters can be determined based on the characterization of any given cell type. In one specific example, a square wave probe is applied to the battery for a single cycle of about 30 milliseconds. In other words, the detection signal may include a square pulse of a certain current and a negative square pulse of a certain current. The pulses may have the same duration, for example, 15 milliseconds per pulse, or may have different durations. The detection signal may be only positive pulses (current to the battery), or only negative pulses (discharge current from the battery). Each pulse may contain current of the same magnitude, or the pulses may be asymmetric. Although other detection signals are possible, square pulses or square waves have harmonic content over a wide frequency range and are efficiently generated by the range of conventional charging hardware topologies. In general, the purpose of the detection signal is to introduce a wide spectrum of harmonic content into the battery very simply and discretely in order to evaluate the impedance of the battery to various harmonics. Therefore, whether it is a square wave, a square pulse, or other signal, the detection signal is intended to briefly introduce a harmonic spectrum into the battery. In the case of a square wave centered at zero amperes, there may also be equal magnitudes of current entering and leaving the battery, with little or no net charge effect. The idea is to detect the battery without changing the state of charge of the battery. Where changing SOC is similarly acceptable, for example, at less than 100% SOC and in the appropriate charging temperature regime, a certain net charge is possible and acceptable. When probing is infrequent and the net charge is therefore negligible, a certain negligible net charge from the probe signal is similarly acceptable. In some arrangements, a series of different probes containing different harmonic content may be injected. Although uncontrolled and/or high frequency harmonics may have a deleterious effect on the battery, for the purpose of obtaining an impedance spectrum, the system applies square pulses only for very short durations, thereby substantially avoiding such effects.

In the presence of the detection signal, the system measures the current and voltage at the battery terminals (operation 1104). The current and voltage signals are captured in the time domain. For each of the current and voltage measured in the presence of the detection signal, the system obtains a spectrum, from which the system can further generate an impedance spectrum (operation 1106). In one example, the system generates a domain transform of the current and voltage signals to generate a voltage spectrum and a current spectrum. The domain transform may be a discrete wavelet transform using a Morlet wavelet. In some examples, the wavelet may also be viewed as a Gabor wavelet or a complex Morlet wavelet. In one possible embodiment, the system may use fixed-point arithmetic to generate an impedance spectrum, which may allow the use of a relatively low-cost and simpler microcontroller or other computing platform that is more typical of some charging environments, where a large amount of computing power would otherwise be unnecessary or conventionally available.

The system generates an impedance spectrum from the frequency spectrum of the current and voltage signals (operation 1106). In one example, the impedance spectrum is generated by dividing the voltage spectrum by the current spectrum. More specifically, the complex voltage values at various frequencies are divided by the complex current values at the same frequency to generate the impedance at various frequencies. This can generate a complex-valued impedance spectrum. In some examples, it is sufficient to limit the generation of the impedance spectrum to a discrete frequency range (e.g., 200 Hz to 3 kHz).

Regardless of the technique, the system generates an impedance spectrum that identifies the impedance of the battery to harmonics of a particular frequency of a signal applied to the battery. Thus, in a simplified example, in a square pulse probe signal applied to the battery, there will be multiple harmonics. Through the techniques discussed herein, the system generates discrete impedances of the battery to some or all of the discrete harmonics in the probe signal. The spectrum broadly shows the resistance of the battery to a charging signal of a particular frequency. The battery may have more or less impedance (more typically resistance) to different frequency harmonics of the probe signal.

Based on the impedance spectrum, the system can identify specific harmonics for defining the leading edge of the charging portion of the signal (operation 1108). In order to determine the shape of the leading edge of the charging signal, the system determines the optimal frequency based on the impedance spectrum generated from the detection signal. In one specific example, the optimal frequency is the frequency associated with the lowest impedance (specifically, in some embodiments, reactance) in the impedance spectrum. Therefore, the system selects the frequency associated with the lowest impedance. It should be understood that there may be examples in which the system can actually evaluate the admittance (e.g., the highest admittance or the imaginary part of the admittance - susceptance). In general, a charging signal applied to a battery with a shape of a frequency associated with a lower impedance will more efficiently transfer energy for charging than a frequency associated with a higher impedance. Subsequently, the optimal frequency is set to the leading edge of the charging signal or the charging portion of the mixed signal. Therefore, the leading edge 1010 defines a portion of a sinusoidal curve at the identified frequency, as shown in the examples of Figures 10A and 10B.

In addition to the shape of the leading edge of the charging portion, the system also determines the overall properties of the signal including the length of time of the rest period relative to the charging time (including the shaped portion and the main body), the overall signal period, and other properties. In one possible example, the period and rest period of the charging signal are preset and are based on battery characterization. The period of the charging signal includes a shaped leading edge and a main body following the shaped leading edge. In various possible examples, the charging portion may fall within the range of hundreds of microseconds to tens of milliseconds. The entire cycle includes the charging portion and the rest period (or heating portion). The rest period (or heating portion) may fall within the range of hundreds of microseconds to tens of milliseconds. In other possible examples, the cycle may fall within the range of hundreds of microseconds to tens of milliseconds. The peak current at the peak of the shaped leading edge and the main body of the charging portion of the battery cell may be about 20A, but the peak current value depends on the battery cell type, temperature, characteristics, and other factors, and may therefore be significantly different from the example peak current. An example of determining the charging current (including the peak current) is discussed below.

The method of determining the shape of the leading edge may be repeated throughout a heating or charging cycle, periodically, intermittently, when various targets (SOC or other) are reached, or otherwise. In one particular instance, the detection signal and subsequent operations (1104-1110) are repeated at approximately every 1/2% to 1% SOC change. In another instance, the detection signal and subsequent operations are performed over time (e.g., every 5 seconds, every 30 seconds, or every 60 seconds). The frequency of the detection signal and subsequent operations may change over time. For example, as the battery cell heats, the battery cell may change more quickly, and therefore the detection rate, etc. may change. The detection rate may also change when the battery cell approaches full charge.

Aspects of the present disclosure also relate to a method of generating a current level for a charging signal, wherein the current level is set so that the battery does not overheat during a charging cycle. The method can be used in conjunction with the techniques described herein, for example by setting the current level of a shaped hybrid charging and heating signal or a shaped charging signal. The method can also be used to set the current level of any form of charging signal to address battery heating that occurs during charging in many different charging situations and to not overheat the battery during charging, as well as other advantages alone or in combination.

First, referring to FIG. 12 , method 1200 begins by accessing battery temperature and ambient temperature (operation 1202 ). The technique may consider battery temperature and ambient temperature, battery temperature only, or other parameters. As mentioned herein, the battery temperature may be obtained or more generally accessed in many possible ways. The ambient temperature may be obtained from a temperature sensor positioned to detect the ambient temperature in the environment of the device containing the battery to be charged. The ambient temperature may also be accessed from a third-party device (e.g., a temperature sensor of some form close to the device to be charged), and the temperature signal may be provided by means of a signal (e.g., Bluetooth or WiFi), etc. In some arrangements, the ambient temperature may be obtained by means of a network connection, such as from a third-party service accessible via a network connection. In any case, the system may access one or both of the battery temperature and the ambient temperature. The system may also access an estimate of the ambient temperature over time.

The system then uses the battery temperature and the ambient temperature to obtain a maximum current for charging the battery (operation 1204). The maximum current is the current at which the battery will remain below a maximum threshold temperature during charging if charged at or below the maximum current. The maximum threshold temperature may be, for example, a specified maximum temperature above which charging is interrupted. The maximum threshold temperature may also be some other specified maximum temperature that the system attempts not to exceed.

The maximum current may take into account the state of charge and may identify a charging current that, when applied to the battery, will not cause the battery to heat above a maximum threshold temperature at the end of a charging cycle. Thus, for example, at the same temperature, the maximum current may be higher at a relatively high starting state of charge than a relatively lower maximum current at a lower starting state of charge.

In one example, the system accesses a model, which may be in the form of an equation (e.g., a quadratic equation including variables for battery temperature and ambient temperature). The model may also be a lookup table that receives battery temperature values and ambient temperature values as keys and identifies charging current values based on the keys. In one example, the model may be based on battery characterization that identifies the temperature signature of the battery across a spectrum of charging conditions and how those charging conditions affect the battery temperature.

The model generates a maximum value for the charging current in response to the battery temperature and the ambient temperature. In one example, the model may assume a fully discharged state, and the identified charging current value represents the current at which the battery can be charged to a fully charged state without exceeding a maximum threshold temperature. The system may also accept a state of charge and generate a current value to achieve a full charge without exceeding a threshold temperature. In this example, the current value may be slightly greater than the current value that would be from a fully discharged state. One advantage of the technique that does not take into account the state of charge is that the system can operate in a manner that will default to a current that will not exceed a temperature threshold and does not require access to an accurate ongoing state of charge assessment, which can be beneficial in various situations, such as when the battery is first charged and a current or accurate SOC is not available.

The system uses the ambient temperature to account for the battery's environment and its effect on battery heating. In one example, the maximum current is set at the beginning of the charge cycle and is not updated during the charge cycle. In another example, the system may update the maximum current value based on time, charge state progress, changes in ambient temperature or battery temperature, and other measurements. In another example, the maximum current value may be one of the other values used to determine the charge current at any given point in the charging sequence.

It should be noted that the maximum current or any other current value may be limited by the capabilities of the charging environment. Therefore, the system may also access a current limit value based on the charging environment (operation 1206). In some examples, the charging hardware itself may be limited in the amount of charging current it can supply. For example, the system may be able to charge from a higher current source, but is connected to a lower current source that limits the maximum charging current that the system can provide. In other examples, other limitations may be imposed on the system that indicate a current limit that can be used to charge the battery. For example, the charging hardware may be limited based on limitations of the power source. Regardless, the system may take into account system-based current limitations. If the maximum current from operation 1204 exceeds the system current limit, this becomes relevant, and the system current limit effectively becomes the maximum current.

Finally, the system may access a third current parameter associated with the amount of (e.g., maximum) charging current to the battery based on its current temperature (operation 1208). As mentioned herein, a battery below or within a certain temperature threshold cannot be charged at the same rate as when it is above a threshold or threshold range. As the battery heats up, a higher charging current becomes available. Any given battery type may be characterized by identifying the maximum charging current that can be applied without damaging the battery based on its temperature. As mentioned herein, temperature plays a role in the ability of the battery to receive a charge. In this example, the system accesses a model that determines the maximum current at the current time based on the current battery temperature. Where the current limit discussed above identifies the maximum current that can be applied to maintain the battery at or below a certain threshold in the future (e.g., when the battery reaches a fully charged state), the model in this example identifies the maximum charging current that the battery can accept at the current time based on its current temperature. The value may change as the battery heats up. In addition, if the value is below a threshold (e.g., T<T1 discussed above), the model will indicate that the charging current is not applied until the battery reaches or exceeds the threshold.

Thus, in summary and in one example, the system can identify three maximum current limits: (1) a first current limit, which is the maximum current at which the battery can be charged and not exceed a certain temperature in the future, taking into account the battery temperature and the ambient temperature; (2) the maximum current that the system can support; and (3) the maximum charging current that can be applied to the battery based on the current temperature of the battery.

The system then selects the minimum of the three resulting current limits. Thus, for example, at relatively low battery temperatures and in a cold environment, the first current limit may be relatively higher than the third current limit because the battery is initially cool and cannot accept a maximum charge, and the ambient environment is relatively cold so that the battery temperature will not heat up as it would in a relatively warm ambient environment. Therefore, the system selects the third current limit because charging at the relatively high first current limit will exceed the third current limit. However, as the battery warms up, the third current limit value may rise to a level that exceeds the first value, in which case the system will select the first current limit instead of the third current limit. In this way, the system, while it may charge instantaneously at a higher rate, will not select a current that will cause the battery to overheat later in the charging cycle. If in any or any situation, the maximum current from the system is less than either or both of the first and third limits, the system will use the second current limit because the system cannot provide the higher first or third limits.

As mentioned above, when in hybrid heating/charging mode or charging-only mode, the system applies a complex shaped charging signal having a charging portion and a heating portion or a rest portion, either or both of which may include a positive offset so that a certain charging current is delivered during the heating portion or the charging portion. The maximum charging current value may be converted to various portions of the complex charging signal.

In one specific example, the maximum charging current is the average value of the total complex charging signal (operation 1212). The system sets the peak current of the charging portion of the signal based on the average value (maximum charging current) and other parameters of the charging signal, such as the overall period and rest period of the time of the charging portion of the signal and the time of the rest portion of the signal, the duty cycle, or some combination thereof. As mentioned above, when determining the shape of the charging portion, the system can access the time parameters of the overall signal, such as the overall period of the signal and the rest period. Using this information, the system can determine the time of the charging portion (shaped portion and main portion) of the signal.

In one possible example, the system uses the current limit (average current) to set the peak current for the main portion of the signal while also taking into account the charge transfer that occurs during the shaped leading edge. For comparison purposes, if the system were to select an extremely high frequency harmonic for the shaped leading edge (which would appear as a conventional square wave), and the system determined a 50% duty cycle (50% for the charging portion plus the main portion and 50% for the rest portion), where the current limit is set to 5A, the peak current for the charging portion would be 10A. However, for a mixed charging and heating signal or charging signal, the system will generate relatively low frequency harmonics because the shaped leading edge (not the high frequency sharp leading edge of a square wave) delivers such charging energy during the shaped leading edge as well as during the main portion of charging. In the same example of a 50% duty cycle, if the average current is set to 5A, the peak current at the upper portion of the shaped leading edge as well as the main portion would be greater than 10A because some charge is delivered during the shaped leading edge of the charging portion, with the remainder of the charge being delivered during the main portion of charging. In this example, the system considers both the shaped leading edge and the body within 50%, and therefore the peak current of the body is higher than 10A because less energy is transferred during the shaped leading edge portion compared to a conventional square pulse. Thus, in determining the peak current, the system considers the charge transferred during both the shaped portion and the body portion of the charging portion of the signal.

In almost all examples, the peak current will be greater than the maximum current selected from operations 1204-1209. In some examples, the system may determine that the peak current is greater than what can be supplied by the system's hardware. In such examples, the system may generate a positive charging current offset for the rest period so that the average current can be achieved over the entire cycle of the signal (charging portion and rest portion). In other examples, the system may adjust the overall cycle so that the rest period remains the same, but the charging portion is increased so that the average current can be achieved over the cycle of one signal by extending the time that the charging signal portion is delivering the charging current. In another example, the system may maintain the same overall cycle while shortening the rest period.

According to various aspects of the present disclosure, a system may involve a controlled discharge signal from a battery, whether as part of a heating sequence or to power a load, the controlled discharge signal including various possible harmonics (e.g., harmonic components at a specified frequency or a discharge signal shaped in other ways). Referring again to FIGS. 1-3 and 13 , the system may include a battery 104 ( 1304 ) and a controller 100 ( 1300 ) that manages the discharge signal of the battery alone or in combination with a charging signal when in the context of heating, but in general operation of a system powered by the battery, the discharge control may be used to optimally discharge the battery. The controller may be some form of processing unit and may be part of a control system separate from the battery, or may be integrated with the battery in a battery management system. Regardless of the control configuration, the entire system provides a discharge signal, wherein one or more of the leading edge of the signal, other aspects of the edge of the signal, harmonics including the body of the signal, and/or the trailing edge of the signal may be tuned to a particular frequency, which may be attributed to reducing and/or minimizing the impedance properties of the battery in the presence of the discharge signal during operation of the system, or otherwise tailored in various possible instances to initially heat the battery so that it can transition to charging or otherwise powering a load. Regardless, the harmonic components of the discharge signal are controlled, or more generally, the discharge signal has an unconventional non-DC property. One or more harmonic components may be based on an evaluation of the complex impedance or other properties of the battery in the presence of the discharge harmonics to select and control the harmonic components of the discharge signal that reduce or otherwise minimize the impedance property (e.g., complex impedance) in the presence of the discharge signal when powering a load, or produce harmonics with relatively high impedance so that when in a heating mode of operation, energy is consumed primarily as heat, or other harmonic properties are controlled for various possible reasons. Controlling discharge in these ways has several possible advantages to the battery, including optimizing heat during discharge, enhancing battery life and capacity, increasing discharge current magnitude, and other advantages over discharging the same type of battery using conventional techniques.

However, in such a harmonically controlled discharge signal environment, conventional downstream systems may not be suitable for receiving such harmonically controlled signals from the battery. Therefore, in one example, the discharge signal conditioning element 1302 is positioned between the battery 1304 and the load 1306 (144), or integrated within the load. The discharge signal conditioning element is used to adjust the unconventional discharge signal suitable for the load or the element that uses energy from the battery to power the load. In one example, and with reference to FIG. 1, the discharge signal conditioning element is a suitable capacitor 122 or capacitor bank, or other energy storage element, which is positioned to receive the discharge signal from the battery and store enough energy to meet the needs of the load. In one example, the load system 1306 may also include a DC to AC converter or other form of power conversion 146 (FIG. 1) to power the load, and the capacitor or capacitor bank is positioned between the battery and the DC to AC converter component of the load system. Subsequently, the harmonically controlled discharge signal is used to charge the capacitor bank, and the capacitor bank directly provides the DC source required by the DC to AC converter or the load. The size and arrangement of the capacitor bank are designed according to the power requirements of the load.

In another example, the load is configured to receive a harmonically tuned discharge signal from the battery. For a DC driven load, for example and similar to the embodiments discussed above, the load may include a capacitor 122 at the input to the load that removes harmonic content from the discharge signal. In other examples, the discharge signal may be controlled by a buck or boost circuit driving the load. In such examples, the buck or boost circuit may be controlled to customize the harmonic content of the discharge signal and simultaneously tune the discharge signal to the load. Although the signal conditioning element and the load system are shown as separate blocks, the signal conditioning may be integrated with the load system.

In some examples, a heating waveform, particularly a sinusoidal heating waveform, can be set to a frequency based on a combination of real and imaginary components of an impedance or to include frequency properties based on a combination of real and imaginary components of an impedance. Specifically, with respect to admittance, the heating waveform frequency can be based on a real admittance (conductance) response and an imaginary admittance (susceptance) response. The discussion is set forth in the context of admittance (specifically, conductance and susceptance), but it should be understood that it can also be applied to resistance (the inverse of conductance) and reactance (the inverse of susceptance).

14A is a graph showing the real admittance (conductance) response 1400 of a sinusoidal signal applied to an example lithium ion cell at a 50% state of charge over a frequency spectrum. As shown in FIG14A , it can be seen that at frequency A and toward frequency B, the conductance changes from a relatively high first conductance value at frequency A to a relatively low second conductance value at frequency B, where the conductance continues to decrease at frequencies greater than frequency B. In the illustrated graph, frequency A is located at an inflection point 1402 in the conductance response curve, where the conductance rises with increasing frequency until frequency A, and then begins to decrease at frequencies greater than frequency A. In the illustrated example, the conductance at frequency A is also at a local maximum.

14B , it can be seen that at about frequency A, as the frequency increases to frequency B, for the same representative lithium-ion cell at 50% SOC, the susceptance changes from a relatively low first susceptance value to a local maximum peak susceptance value at frequency B. In the illustrated graph, frequency B is located at an inflection point 1402 in the susceptance response, where the susceptance rises with increasing frequency until frequency B, and then begins to decrease at frequencies greater than frequency B.

In various possible examples, the sinusoidal frequency of the heating signal discussed above in various embodiments may be established based on a conductance response, a susceptance response, or a combination of both responses.As already mentioned, the discussion identifies admittance which also applies to the reciprocal values of resistance and reactance.

In one possible example, the heating frequency may be set to a value between the frequency at which the conductance is at a peak value (e.g., the frequency at A) and the frequency at which the susceptance is at a peak value (e.g., frequency B). In another aspect, the heating frequency may be set to a frequency value between the inflection point frequency in the conductance response of the battery and the inflection point frequency in the susceptance response of the battery. In the frequency region between A and B, the conductance decreases relatively steeply, and the susceptance increases relatively steeply. The heating frequency may be selected from a value in the frequency region between A and B.

In a more specific example, the frequency of the heating signal is within a range around the midpoint between frequencies A and B (e.g., frequency X). Referring to FIGS. 14A and 14B , the conductance is peaked at about 10 ³ Hz, and the susceptance is peaked at about 10 ⁴ Hz. In this particular reference, it can be seen that the conductance peaks at frequencies less than 10 ³ Hz, and the susceptance peaks at frequencies less than 10 ⁴ Hz, where the term about refers to the fact that the precise scale of the graph is not in granularity to specify exact frequencies, and the figures are actually used to illustrate general conductance and susceptance curve characteristics. However, in this example, the heating frequency is chosen to be frequency X, which is approximately midway between frequency A and frequency B.

From an electrochemical and electrodynamic perspective, at frequency A, electrons can move a greater total distance in a charged cell, making it easier to offset the charge of the applied electric field. Therefore, and because none of the other materials in the cell exhibit polarization, the cell cannot support the high susceptance required for more uniform and multi-component charge propagation and electron mobility. At frequency B, susceptance and polarization are maximum, but electron mobility is greatly reduced, thereby reducing the heating of I ² R from the current collector. At frequencies between A and B, for example, at X, conductivity and I ² R heating remain high, while susceptance is much higher than that at frequency "A", indicating that additional components and electrode areas participate in heat generation. It is well known that susceptance arises from the curling of electrodes in cylindrical cells, and therefore, it can be assumed to be relatively uniform throughout the cell. Frequencies within the selected range can also be fully removed from the time constants associated with chemical mechanisms, electrochemical mechanisms, and possibly electrokinetic mechanisms, thus avoiding nucleation and SEI growth during heating.

The frequency region between the local maximum (inflection point) of conductance and susceptance defines an area where frequencies can be selected to balance these problems and advantages. The frequency region can also be based on the conductance or susceptance alone. For example, when identifying a local maximum at a conductance inflection point, a frequency within a certain range of the frequency at the inflection point can be selected. In a more detailed example, the frequency can be greater than the frequency at the inflection point. The degree to which the frequency is greater can be set to a fixed offset, can be based on a certain difference (e.g., percentage) below the conductance value at the inflection point, etc. With respect to susceptance, when identifying a local maximum at a susceptance inflection point, a frequency within a certain range of the frequency at the inflection point can be selected. In a more detailed example, the frequency can be less than the frequency at the inflection point. The degree to which the frequency is less can be set to a fixed offset, can be based on a certain difference (e.g., percentage) below the susceptance value at the inflection point, etc. With respect to conductance or susceptance, the heating frequency can also be selected based on the local minimum of the conductance or susceptance, wherein a frequency less than the selected local minimum of the conductance or a frequency greater than the selected local minimum of the susceptance is selected. In both FIG. 14A and FIG. 14B , the local minimum of susceptance is similar to (slightly less than) the frequency of the local maximum 1402 of conductance.

The term "about" will be understood by those of ordinary skill in the art and will vary to some extent depending on the context in which it is used. As used herein, when referring to values such as frequency, temperature, current, etc., the term "about" is meant to cover ±10% variations from the specified value, including ±5%, ±1%, and ±0.1%, as such variations are suitable for performing the disclosed methods.

In various examples above, including the discussion of Figures 14A and 14B, the heating frequency can be selected based on a variety of criteria. In some examples, the frequency is based on the inflection point or midpoint or some other criterion, and it should be recognized that there is a certain flexibility about the precise number selected. Thus, for example, the frequency of the reference inflection point can be located at the inflection point or at about the inflection point, which means that it can be within 10% of the value, or other percentage values mentioned above. Similarly, if at the midpoint between the frequencies, the value can be within 10% of the midpoint to either side.

With reference to FIG. 15 , a detailed description of an example computing system 1300 having one or more computing units that can implement various systems and methods discussed herein is provided. The computing system 1500 can be part of a controller, can be in operative communication with various embodiments discussed herein, can run various operations related to the methods discussed herein, can run offline to process various data for characterizing a battery, and can be part of an overall system discussed herein. The computing system 1500 can process various signals discussed herein and/or can provide various signals discussed herein. For example, battery measurement information can be provided to such a computing system 1500. The computing system 1500 can also be applicable to, for example, controllers, models, tuning/shaping circuits discussed with respect to the various figures, and can be used to implement various methods described herein. It should be understood that specific embodiments of these devices can be different possible specific computing architectures, all of which are not specifically discussed herein, but will be understood by those of ordinary skill in the art. It should be further understood that a computer system can be considered and/or include an ASIC, FPGA, microcontroller, or other computing arrangement. In such various possible implementations, more or fewer components discussed below may be included, interconnections and other changes made, as will be understood by one of ordinary skill in the art.

Computer system 1500 can be a computing system capable of executing a computer program product to execute a computer process. Data and program files can be input into computer system 1500, and the computer system reads files and executes programs therein. Some of the elements of computer system 1500 are shown in Figure 15, including one or more hardware processors 1502, one or more data storage devices 1504, one or more memory devices 1506 and/or one or more ports 1508-1512. In addition, other elements that those skilled in the art will recognize may be included in computing system 1500, but they are not clearly described in Figure 15 or further discussed in this article. The various elements of computer system 1500 can communicate with each other by means of one or more communication buses, point-to-point communication paths or other communication components that are not clearly described in Figure 15. Similarly, in various embodiments, the various elements disclosed in the system may or may not be included in any given embodiment.

Processor 1502 may include, for example, a central processing unit (CPU), a microprocessor, a microcontroller, a digital signal processor (DSP), and/or one or more internal levels of cache. There may be one or more processors 1502, such that processor 1502 includes a single central processing unit, or multiple processing units capable of executing instructions and performing operations in parallel with each other, which is generally referred to as a parallel processing environment.

The presently described techniques, in various possible combinations, may be implemented at least in part in software stored on the data storage device 1504, stored on the memory device 1506, and/or transmitted via one or more of the ports 1508-1512, thereby transforming the computer system 1500 in FIG. 15 into a special-purpose machine for performing the operations described herein.

The one or more data storage devices 1504 may include any non-volatile data storage device capable of storing data generated or employed within the computing system 1500, such as computer executable instructions for executing computer processes, which may include instructions for both application programs and an operating system (OS) that manages the various components of the computing system 1500. The data storage device 1504 may include, but is not limited to, a magnetic disk drive, an optical disk drive, a solid state drive (SSD), a flash drive, and the like. The data storage device 1504 may include removable data storage media, non-removable data storage media, and/or an external storage device available via a wired or wireless network architecture with such computer program products, including one or more database management products, network server products, application server products, and/or other additional software components. Examples of removable data storage media include compact disk read-only memory (CD-ROM), digital versatile disk read-only memory (DVD-ROM), flash drives, and the like. Examples of non-removable data storage media include internal magnetic hard disks, SSDs, and the like. The one or more memory devices 1506 may include volatile memory (eg, dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and/or nonvolatile memory (eg, read only memory (ROM), flash memory, etc.).

A computer program product containing mechanisms for implementing systems and methods according to the presently described technology may reside in data storage device 1504 and/or memory device 1506, which may be referred to as a machine-readable medium. It should be appreciated that a machine-readable medium may include any tangible, non-transitory medium capable of storing or encoding instructions to perform any one or more operations of the present disclosure performed by a machine, or any tangible, non-transitory medium capable of storing or encoding data structures and/or modules utilized by or associated with such instructions. A machine-readable medium may include a single medium or multiple media (e.g., a centralized or distributed database and/or associated caches and servers) storing one or more executable instructions or data structures.

In some embodiments, the computer system 1500 includes one or more ports for communicating with other computing, network, or vehicle devices, such as input/output (I/O) ports 1508, communication ports 1510, and subsystem ports 1512. It should be appreciated that ports 1508-1512 may be combined or separated, and that more or fewer ports may be included in the computer system 1500. The I/O port 1508 may be connected to an I/O device or other device through which information is input to or output from the computing system 1500. Such I/O devices may include, but are not limited to, one or more input devices, output devices, and/or environmental transducer devices.

In one embodiment, the input device converts human-generated signals such as human voice, body movement, physical touch or pressure into electrical signals as input data input to the computing system 1500 via the I/O port 1508. In some examples, such input may be different from the various systems and methods discussed with respect to the previous figures. Similarly, the output device may convert electrical signals received from the computing system 1500 via the I/O port 1508 into signals that can be sensed or used by the various methods and systems discussed herein. The input device may be an alphanumeric input device that includes alphanumeric keys and other keys for transmitting information and/or command selections to the processor 1502 via the I/O port 1508.

The environmental transducer device converts one form of energy or signal into another form of energy or signal for input into or output from the computing system 1500 via the I/O port 1508. For example, an electrical signal generated within the computing system 1500 may be converted into another type of signal, and/or vice versa. In one embodiment, the environmental transducer device senses a characteristic or aspect of the environment local to or remote from the computing device 1500, such as battery voltage, open circuit battery voltage, charging current, battery temperature, light, sound, temperature, pressure, magnetic field, electric field, chemical characteristic, etc.

In one embodiment, the communication port 1510 can be connected to a network by means of which the computer system 1500 can receive network data useful for executing the methods and systems described herein and transmitting information and network configuration changes determined thereby. For example, charging protocols can be updated, battery measurement or calculation data can be shared with external systems, etc. The communication port 1510 connects the computer system 1500 to one or more communication interface devices, which are configured to transmit and/or receive information between the computer system 1500 and other devices via one or more wired or wireless communication networks or connections. Examples of such networks or connections include, but are not limited to, Universal Serial Bus (USB), Ethernet, Wi-Fi, Near Field Communication (NFC), Long Term Evolution (LTE), etc. One or more such communication interface devices may be utilized via communication port 1510 to communicate with one or more other machines directly through a point-to-point communication path, through a wide area network (WAN) (e.g., the Internet), through a local area network (LAN), through a cellular (e.g., third generation (3G), fourth generation (4G), fifth generation (5G)) network, or through another communication component.

The computer system 1500 may include a subsystem port 1512 for communicating with one or more systems related to charging a device to control the operation of the device and/or exchanging information between the computer system 1500 and one or more subsystems of the device according to the methods and systems described herein. Examples of such subsystems of a vehicle include, but are not limited to, motor controllers and systems, battery control systems, etc.

The system illustrated in Figure 15 is only one possible example of a computer system that can be employed or configured according to various aspects of the present disclosure. It should be understood that other non-transitory tangible computer-readable storage media storing computer-executable instructions can be utilized to implement the currently disclosed technology on a computing system.

Embodiments of the present disclosure include various operations described in this specification. The operations may be performed by hardware components or may be embodied in machine executable instructions, which may be used to cause a general or special purpose processor programmed with the instructions to perform the operations. Alternatively, the operations may be performed by a combination of hardware, software, and/or firmware.

Various modifications and additions may be made to the discussed exemplary embodiments without departing from the scope of the present disclosure. For example, although the embodiments described above, also referred to as implementations or examples, refer to specific features, the scope of the present invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Therefore, the scope of the present invention is intended to cover all such alternatives, modifications and variations, as well as all equivalents thereof.

Although specific embodiments, examples and embodiments (terms used synonymously herein) are discussed, it should be understood that this is done for illustrative purposes only. Those skilled in the relevant art will recognize that other components and configurations can be used without departing from the spirit and scope of the present disclosure. Therefore, the description and drawings are illustrative and should not be construed as limiting. Many specific details are described to provide a thorough understanding of the present disclosure. However, in some examples, well-known or conventional details are not described to avoid fuzzy descriptions.

Reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. The appearances of the phrase "in one embodiment" or similarly "in one instance" or "in an example" or similar phrases in various places in this specification are not necessarily all referring to the same embodiment, nor are separate embodiments or alternative embodiments mutually exclusive of other embodiments. In addition, various features are described that may be exhibited by some embodiments but not by others.

The terms used in this specification sheet usually have their general meaning in the art in the context of the present disclosure and in the specific context of using each term. For any one or more of the terms discussed herein, alternative language and synonyms can be used, and no matter whether the terms are described in detail or discussed herein, special meanings should not be added. In some cases, synonyms for specific terms are provided. The narration of one or more synonyms does not exclude the use of other synonyms. The examples used anywhere in this specification sheet (including the examples of any terms discussed herein) are merely illustrative and are not intended to further limit the scope and meaning of the present disclosure or any example terms. Similarly, the present disclosure is not limited to the various embodiments provided in this specification sheet.

In the case of not being intended to limit the scope of the present disclosure, the examples of instruments, equipment, methods and related results thereof according to the embodiments of the present disclosure are given below. It should be noted that, for the convenience of the reader, titles or subtitles may be used in the examples, which should never limit the scope of the present disclosure. Unless otherwise defined, technical terms and scientific terms used herein all have the same meaning as those of ordinary skill in the art to which the present disclosure belongs. In the case of conflict, this document (including definitions) shall prevail.

Various features and advantages of the present disclosure are set forth in the description, and in part will be obvious from the description, or may be learned by practicing the principles disclosed herein. The features and advantages of the present disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.

Claims (33)

1. A method for heating a battery, comprising: A repetitive signal is generated for application to a battery, the repetitive signal comprising a first portion and a second portion within a cycle, the first portion defining a sinusoidally shaped leading edge rising into a main portion, the main portion terminating in a falling edge, the first portion defining a first percentage of the cycle, the second portion comprising an alternating current following the falling edge of the first portion, the second portion defining a second percentage of the cycle, wherein the first percentage and the second percentage constitute the cycle. The method according to claim 1 , wherein the repetitive signal is a current signal. 3. The method of claim 1, wherein the sinusoidally shaped leading edge has a first frequency associated with a first harmonic having a relatively low impedance when applied to the battery compared to other harmonics. 4. The method of claim 1 wherein the alternating current is centered around approximately zero amperes. 5. The method of claim 1, wherein the alternating current defines a sine wave having a positive current portion and a negative current portion. 6. The method of claim 1, wherein the alternating current is applied with a positive direct current offset. 7 . The method of claim 3 , wherein the sinusoidally shaped leading edge changes to a second frequency of the second harmonic when an impedance of the second harmonic is lower than the impedance of the first harmonic. 8. The method of claim 1, wherein the second portion is changed from alternating current to zero charging current when a temperature of the battery rises to about a threshold value. 9. The method of claim 8, wherein the temperature of the battery is based on a sensed temperature. 10. The method of claim 8, wherein the temperature of the battery is based on an application time of the repetitive signal, wherein the second portion includes the alternating current. 11 . The method of claim 1 , wherein a repeating pattern is applied to the battery when the battery temperature is below a threshold. 12. The method of claim 1, further comprising generating an alternating current signal to apply to the battery below a temperature, and then generating the repetitive signal including the first portion and the second portion when the battery reaches the temperature. 13. A method for charging a battery, comprising: applying a detection signal to the battery, the detection signal comprising a plurality of harmonics, the plurality of harmonics comprising at least a first harmonic and a second harmonic; obtaining a voltage response and a current response at the battery based on the detection signal; generating an impedance spectrum including at least a first impedance of the first harmonic and a second impedance of the second harmonic based on the voltage response and the current response, the first impedance being less than the second impedance; and A charging signal is generated for application to the battery, the charging signal comprising a sinusoidally shaped leading edge of the frequency of the first harmonic. 14. The charging method of claim 13, wherein the charging signal is a repetitive signal having the sinusoidally shaped leading edge followed by a body portion, the body portion followed by a heating portion comprising an alternating current waveform. 15. The charging method of claim 14, wherein the AC waveform is centered around zero amperes. The charging method according to claim 13 , wherein the detection signal is a square wave centered at zero ampere. 17. The charging method of claim 16, wherein the square wave is at a 50% duty cycle for a period of about 30 milliseconds. 18. A method of charging a battery taking temperature into account, comprising: Based on the current battery temperature, identifying a first charging current that will not overheat the battery after a period of time of continuous charging at a maximum current, and identifying a second charging current that can be used at the current temperature of the battery; and A charging signal for the battery is initiated at the lower of the first charging current or the second charging current. 19. The charging method of claim 18, further comprising identifying the first charging current based on ambient temperature. 20. The charging method of claim 18, wherein the first charging current and the second charging current are limited by the ability to supply either current. 21. The charging method according to claim 18, wherein the first charging current or the second charging current is an average current of a repetitive portion of the charging signal, the repetitive portion comprising a first portion followed by a second portion, the first portion comprising a sinusoidal leading edge followed by a main portion. 22. The charging method of claim 21, wherein the second portion is a rest portion at zero ampere. 23. The charging method according to claim 22, wherein the average current is used to define the peak current of the sinusoidal leading edge and the main body portion. 24. The charging method of claim 21, wherein the second portion is a non-zero DC charging current, the average current defines a peak current of the sinusoidal leading edge and the main portion, and the non-zero DC charging current. 25. A method of heating a battery, comprising: An alternating current having a frequency greater than a frequency at an inflection point of the conductance response or less than a frequency at an inflection point of the susceptance response is applied to the battery to heat the battery. 26. The method of claim 25, wherein the frequency is greater than a frequency at an inflection point of a conductance response and less than a frequency at an inflection point of a susceptance response. 27. A method of heating a battery comprising applying an alternating current to a battery to heat the battery, the alternating current being at a frequency at which a conductance response of the battery is decreasing and a susceptance response of the battery is increasing. 28. The method of claim 27, wherein the frequency is greater than a frequency at which the conductance response begins to decrease and less than a frequency at which the susceptance response begins to decrease. 29. The method of claim 28, wherein the frequency at which the conductance response begins to decrease is located at an inflection point when the conductance response is a local maximum. 30. The method of claim 28, wherein the frequency at which the susceptance response begins to decrease is located at an inflection point where the susceptance response is a local maximum. 31. The method of claim 27, wherein the frequency is within a range between a first frequency and a second frequency, the first frequency being approximately located at a position where the conductance response of the battery begins to decrease after the conductance response of the battery is increasing, and the second frequency being approximately located at a position where the susceptance response of the battery begins to decrease after the susceptance response of the battery is increasing. 32. The method of claim 31, wherein the first frequency is located at an inflection point of the conductance response where the conductance response transitions from increasing to decreasing. 33. The method of claim 31, wherein the second frequency is located at an inflection point of the susceptance response where susceptance transitions from increasing to decreasing.