JP2025506781A - Systems and methods for controlled battery heating - Patents.com - Google Patents

Abstract

Systems and methods for heating a battery that can be performed alone or in combination with charging or discharging the battery. In some embodiments, the heating involves application of an alternating current waveform, which may be a sine wave, to the battery. In some embodiments, the heating signal is applied at a frequency and/or current that results in little or no net charge to the battery.

Description

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

This application is also a joint venture under 35 U.S.C. § 119(e) with U.S. Provisional Patent Application No. 63/163,011, entitled "Powering A Load from a Battery Discharging with Harmonic Components," filed on March 18, 2021, and U.S. Provisional Patent Application No. 63/313,147, entitled "Systems and Methods for Controlled Battery Heating Sourcing Current To and From the This application is also related to a continuation-in-part application of U.S. Patent Application No. 17/699,016 entitled "System and Methods of Controlled Battery Heating Sourcing Current To and From the Battery and Discharge Signal Conditioning From the Same," filed March 18, 2022, which claims the benefit of priority to U.S. Provisional Patent Application No. 17/699,016 entitled "System and Methods of Controlled Battery Heating Sourcing Current To and From the Battery and Discharge Signal Conditioning From the Same," all of the contents of which are incorporated herein by reference.

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

Countless different types of motorized devices, such as power tools, mobile computers and communication devices, portable electronic devices, and all kinds of motorized vehicles, including scooters and bicycles, use rechargeable batteries as their operating power source. Rechargeable batteries are constrained by a finite battery capacity and must be recharged when depleted. Recharging a battery can be inconvenient because the motorized device often must not be moved during the time it takes to recharge. Depending on the size of the battery, recharging can take several hours. Furthermore, charging a battery is often accompanied by a degradation of the battery's performance. For this reason, considerable effort has been expended in developing battery charging techniques to, among other things, reduce the time it takes to recharge a battery, improve battery performance, and reduce battery degradation due to charging.

For many types of batteries, including lithium-based batteries, charging at low temperatures without damaging the cells is often not possible. In some cases, especially batteries with liquid electrolytes, the electrolyte may freeze. Attempting to charge when the electrolyte is frozen or when the battery temperature is below a certain threshold can also damage the battery through electrode plating. This can be an obvious concern in many use cases where the battery is discharged but the temperature is too low for conventional charging.

Various aspects of the present disclosure were devised with these observations in mind, among others.

One aspect of the present disclosure includes a system for heating a battery, the system comprising a processor in communication with a circuit, the processor configured to heat the battery by controlling the circuit to alternately supply current to the battery and absorb current from the battery by executing instructions, and the battery is heated by a combination of supplying current to the battery and absorbing current from the battery.

Another aspect of the present disclosure includes a battery power system comprising a battery and a processor in operative communication with a charging circuit of the battery, the processor operatively coupled to the charging circuit to control at least one harmonic component of a discharge signal from the battery. The system may further comprise a signal conditioning element disposed 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 disclosure includes a method of charging a battery, the method including alternately supplying and absorbing current from the battery to heat the battery in response to obtaining information indicating whether the battery is chargeable. The method may further include receiving a temperature measurement of the battery that provides information indicating whether the battery is chargeable. In one possible example, obtaining a response from the battery based on application of a signal having a known harmonic provides information indicating whether the battery is chargeable. In another possible example, the response is an impedance response and the information is a correlation of battery temperature to the impedance response. In various embodiments, while impedance or admittance response is discussed, it is to be recognized that the term impedance response includes its inverse admittance response, and the term admittance or admittance response similarly includes its inverse impedance or impedance response.

Another aspect of the disclosure includes a method of charging a battery, the method including applying a harmonically adjusted signal to the battery, the harmonically adjusted signal being comprised of at least one harmonic associated with a conductance response and a reactance response, in response to obtaining information indicative of whether the battery is capable of accepting a charge, to heat the battery. The method may further include receiving a temperature measurement of the battery that provides information indicative of whether the battery is capable of being charged. In another example, obtaining a response from the battery based on application of a signal having known harmonics may provide information indicative of whether the battery is capable of being charged. In one example, the response is an impedance response and the information is a correlation of battery temperature to the impedance response. The at least one harmonic may be at a higher frequency than the motion and diffusion processes of the battery. If the signal is comprised of multiple harmonics, the aggregate of the harmonics may be at a higher frequency than the motion and diffusion processes of the battery.

Another aspect of the present disclosure includes a method of heating a battery, comprising generating and applying to the battery a repetitive signal that defines a sinusoidal leading edge that rises over a period of time into a body portion terminating in a trailing edge and includes a first portion that defines a first percentage of the period, and a second portion that includes an alternating current following the trailing edge of the first portion and defines a second percentage of the period, the first percentage and the second percentage constituting the period.

Another aspect of the present disclosure includes a method of charging a battery, the method including applying a probe signal to the battery, the probe signal including multiple harmonics including at least a first harmonic and a second harmonic. The system/method further includes obtaining a voltage response and a current response at the battery based on the probe signal, generating an impedance spectrum including at least a first impedance at the first harmonic and a second impedance at the second harmonic based on the voltage response and the current response, the impedance spectrum including at least a first impedance at the first harmonic and a second impedance at the second harmonic, the first impedance being lower than the second impedance, and generating and applying to the battery a charging signal including a sinusoidal leading edge at the frequency of the first harmonic.

Another aspect of the present disclosure includes a method of heating a battery, the method including applying an alternating current to the battery at a frequency higher than the frequency at the inflection point in the conductance response or lower than the frequency at the inflection point in the susceptance response to heat the battery. More specifically, the frequency is higher than the frequency at the inflection point in the conductance response and lower than the frequency at the inflection point in the susceptance response.

Yet another aspect of the present disclosure includes a method of heating a battery, the method comprising applying to the battery an alternating current at a frequency that decreases the conductance response of the battery and increases the susceptance response of the battery to heat the battery.

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

Various objects, features, and advantages of the present disclosure described herein will become apparent from the following description of embodiments of the inventive concepts thereof, as illustrated in the accompanying drawings. It should be noted that the drawings are not necessarily to scale or containing every detail, and may depict various features of an embodiment, with emphasis instead being placed on illustrating the principles and other aspects of the inventive concepts. Also, in the figures, the same reference characters may represent the same or similar parts throughout the different drawings. The embodiments and drawings disclosed herein are intended to be considered illustrative, and not limiting.

FIG. 2 is a circuit diagram of a battery heating and charging system, further illustrating the charge path from a power source and the load path, according to one embodiment. FIG. 2 is a circuit diagram of the battery heating and charging system of FIG. 1 further showing a discharge path from the battery along with a load path from a power rail including a power supply. FIG. 3 is a circuit diagram of the battery heating and charging system of FIGS. 1 and 2 further showing the charging and load paths from the power rail (e.g., the capacitor thereon) when the power supply is not providing energy (e.g., current). FIG. 2 is a signal diagram of a first exemplary heating signal including symmetrically shaped charging and discharging current portions according to one embodiment. FIG. 13 is a signal diagram of a second exemplary heating signal including asymmetrically shaped charging and discharging current portions according to one embodiment. FIG. 13 is a signal diagram of a third exemplary heating signal including differently shaped charging and discharging current portions according to one embodiment. FIG. 11 is a diagram showing an example of a profile for heating a battery to a battery temperature at which charging is possible. 4 is a flow chart of a method for heating a battery, according to one embodiment. FIG. 4 is a signal diagram of a first combined charging and heating signal according to one embodiment. FIG. 11 is a signal diagram of a second combined charging and heating signal according to one embodiment. FIG. 2 is a signal diagram of a charging signal including a 0 A quiescent period, according to one embodiment. FIG. 4 is a signal diagram of a charging signal including non-zero current rest periods according to one embodiment. 4 is a flow chart of a method for shaping a charging signal, according to one embodiment. 4 is a flow chart of a method for identifying a charging current level taking into account battery temperature, according to one embodiment. FIG. 1 is a system diagram including signal conditioning elements that convert non-conventional non-DC current from a battery into a signal for consumption by a load that conventionally requires power conversion or a DC signal. 14A and 14B are diagrams of the conductance and susceptance responses of a lithium ion battery used to establish the frequency of a heating signal in one embodiment. FIG. 1 illustrates an example of a computer system that can be used to implement embodiments of the present disclosure.

Disclosed herein are systems, circuits, and methods for heating and charging (recharging) a battery. In this specification, the terms charging and recharging are used interchangeably. Aspects of the present disclosure may provide multiple advantages, alone or in combination, over conventional charging. For example, the charging techniques described herein may allow the battery to be heated to a level sufficient for charging to occur. In some cases, the battery temperature is monitored, and if it is below a threshold, the system initiates a heating sequence before charging and transitions to a charging sequence once the battery is sufficiently warm. The temperature thresholds may be tailored for various battery chemistries. In one example, the heating, combination of heating and charging, and the temperature thresholds for charging may depend on or be related to the freezing temperature of the liquid electrolyte, although various temperature parameters and thresholds are also contemplated. Additionally, some battery chemistries, such as solid-state batteries, do not have a liquid electrolyte but are affected by temperature, and charging at too low a temperature may damage the battery. The system may also include circuit elements that enable charging techniques that can have multiple ramifications, such as reducing the rate at which the anode is damaged and controlling heat generation by the battery by minimizing heat generation at the start of charging or above a certain level, thereby reducing damage to the electrodes and other batteries, and reducing the risk of fire or short circuits.

When discharging a battery, whether for heating or to power a load, aspects of the disclosure further include a discharge signal conditioning element disposed between the battery and the load or incorporated into the load. Traditionally, a battery is discharged to a load by a DC signal, or a DC signal from the battery is converted to an AC signal by an inverter or the like to power an AC motor. However, aspects of the disclosure include non-conventional, non-DC discharge signals, whether for heating or otherwise. The discharge signal conditioning element serves to condition the non-conventional discharge signal to be appropriate for the load or an element that powers the load with energy from the battery.

In one example, various embodiments discussed herein manage energy to and from a battery by generating a controllably shaped charge or discharge signal. The shape may be adjusted based on the battery's impedance effect on various harmonics. Optionally, when heating, the shape (which may include harmonic aspects) during charging or discharging is adjusted to heat the battery while minimizing damage to the battery or achieving other effects. Optionally, when charging, the shape or components of the charging signal (which may also include harmonic aspects) are optimized for charging. When heating, the system may select harmonic attributes associated with relatively high impedance compared to charging, where the charging signal may be controlled 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 such as constant current or constant voltage (DC techniques) are relatively simple to control as they do not involve shaping of the charging signal and do not require the charging and discharging signal shaping techniques discussed herein. The model may be used to verify and/or adjust the control for generating the signal to or from the battery (likely to be combined when heating). While in some cases aspects of the shape and/or composition of the charging signal may correspond to a harmonic (or multiple harmonics) associated with optimal transfer of energy to the battery, the objective of the system is, among other objectives, to efficiently generate and apply to the battery a charging signal of any shape. In other examples, particularly with respect to battery heating that may occur prior to charging, a signal is shaped and/or defined that is intended to minimize or eliminate the occurrence of heating and charging while the battery is being heated in preparation for charging (or discharging). The shape or composition of the signal may be any shape defined by the control, and in some cases the harmonic content is defined but controlled independently.

In one possible implementation, a feedforward technique that utilizes a model to determine the control signals for defining the charge/discharge signals may provide several advantages, including accuracy and speed of signal conditioning. Additionally, this configuration may operate with fewer components than other approaches, resulting in reduced cost and printed wiring board area, among other advantages. Additionally, with this approach, whether or not a model is used, the signal may be conditioned from heating to charging when the battery reaches the appropriate temperature, followed by signal conditioning during battery charging.

Regardless of whether or not a model is used, aspects of the system may further include feedback of battery parameters such as temperature during the heating phase, as well as during transitions to and from the charging phase. Feedback alone or in combination with the model may enable the system to, among other things, adjust for component drift, adjust for effects on circuit components such as temperature, adjust for changes in the battery, and periodically provide additional data to the system and/or model to modify the output. Additionally, the system may use battery temperature to select between heating or charging, and in some cases, transition from a heating phase to a phase where charging is optimized without heating (which may include transition phases for both heating and charging).

The term "battery" can be used in various ways in the art and herein to refer to individual cells having an anode and a cathode separated by an electrolyte (solid or liquid), as well as collections of such cells connected in various configurations. A battery or battery cell is a form of electrochemical device. A battery typically includes repeating units of opposing charge sources and electrode layers separated by an ionically conductive barrier (often a liquid or polymer membrane saturated with the electrolyte). These layers are constructed to be thin, allowing multiple units to occupy the volume of the battery, with each stack of units increasing the available power of the battery. Although many examples are discussed herein as being applicable to batteries, it should be understood that the systems and methods described may be applied to many different types of batteries, ranging from individual cells to batteries including various possible interconnections of cells, such as cells coupled in parallel, series, and series-parallel. For example, the systems and methods discussed herein may be applied to battery packs including many cells arranged to provide a specified pack voltage, output current, and/or capacity. Additionally, the embodiments discussed herein may 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 may also be applied to battery configurations of various structures, such as button or "coin" type batteries, cylindrical cells, pouch cells, and prismatic cells.

1-3 show a battery heating and charging circuit topology according to one embodiment of the present disclosure. The arrows in the figures define the current flow paths in various operating states of the system. In FIG. 1, the system is shown configured to source (charge) current to the battery to power the load. In FIG. 2, the system is shown configured to draw (discharge or absorb) current from the battery through a discharge path to a capacitor on the rail to power the load in the powered-on (connected to the rail) state. In FIG. 3, the system is shown configured to draw current from the battery to a capacitor on the rail in addition to powering the load in the powered-off (not connected to the rail) state. In both FIG. 2 and FIG. 3, there is also an arrow showing a "blip" path to the second transistor on the bottom, which activates the discharge current path.

1, 2 and 3 are schematic diagrams illustrating an exemplary charging signal generator configuration 100 for heating, charging, and/or discharging a battery 104. The generator includes a processing unit, which may include a controller such as a microcontroller, FPGA (field programmable gate array), ASIC (application specific integrated circuit), microprocessor, combinations thereof, or other processing configurations, or more generally, a control unit 106 (which may be in communication with the signal generator 108), which provides control for generating the charging signal from the charging signal shaping circuit 110. The controller may be in communication with a model (which may be part of the generator) to generate control instructions for the charging signal shaping circuit. The control unit including the controller and model (if present) may be an integrated unit. The system may also receive feedback from a battery measurement unit 116, including battery measurements 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), which may be used to obtain impedance measurements and/or to affect heating or charging control. In general, the generator may include or be operatively 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, although an alternating current (AC) source is also contemplated. In various options, the power source 118 may include a DC source that provides a unidirectional current, an AC source that provides a bidirectional current, or a source that provides a ripple current (such as an AC signal with a DC bias so that the current is unidirectional). In general, the power source 118 provides a charging energy (e.g., a current) that may be shaped or defined by the control unit 106 and the circuitry 110 to generate a controllably shaped charging signal for heating, charging, and/or discharging the battery 104. In one example, the controller 106 may provide one or more inputs to the signal generator 108, which controls a switch that generates a pulse to the circuitry 110, which may be referred to as a filter, to generate a shaped signal at the battery.

In some cases, the signal shaping circuit 110 may modify the energy from the power source 118 to generate a signal shaped based on conditions at the battery 104, such as a signal that corresponds at least in part to one or more harmonics based on the impedance when a signal including harmonics or attributes of the harmonics is applied to the battery 104. In an example such as FIG. 1, the circuit 100 may include a battery measurement unit 116 connected to the battery 104 to measure cell voltage and/or charging current as well as other battery attributes such as temperature and to measure, calculate, or otherwise obtain the impedance of the battery 104 based thereon. In one example, the battery characteristics may be measured based on signals to or from the battery. In another example, the battery cell characteristics may be measured as part of a routine to characterize the battery by applying signals with varying frequency attributes to generate a range of battery cell characteristic values associated with different frequency attributes, which may be performed before, during, or periodically during heating, charging, or discharging, and may be used in combination with probing and other techniques. Battery characteristics may vary based on many physical or chemical characteristics of the battery, including the battery's state of charge and/or temperature. Thus, the battery measurement circuitry 116 may be controlled by the controller 106 to determine various battery characteristic values of the battery 104 during heating, recharging, and/or load powering, among other things, and to provide the measured battery characteristic values to the controller 106 or other portions of the generator 100.

During charging, the controller 106 may generate a target charging signal for efficient charging of the battery 104. For example, the controller 106 may use a signal definition characterized by understanding the impedance effect of the battery 104 or the signal on the battery to generate or select a charging signal with attributes corresponding to harmonics associated with an optimal impedance (which may be a wide range of impedances) for energy transfer, which may be associated with a minimum impedance value of the battery 104. To this end, the controller 106 may execute a charging signal algorithm that outputs a shape of the charging signal based on a measured, characterized, and/or estimated state of charge of the battery 104. In general, the signal generator controls a switch to generate a pulse train at 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 thereon. Here, node 136 may be controlled in a similar manner, but with circuit 110 both sourcing and absorbing current with defined impedance attributes to and from the battery. It is to be appreciated that heating also involves transitioning current into and out of the battery, which may be characterized to optimize heating, minimize or eliminate plating, and minimize energy storage in the battery during the heating sequence. Signal generator 108 may generate one or more control signals based on a thermal or charging signal algorithm and provide these control signals to signal shaping unit 110. The control signals may approximate the shaped charging signal determined, selected, or obtained by controller 106, among other functions, by shaping or defining the signal from or to the battery. Charging signal shaping circuit 110 may further filter unwanted frequency attributes from the signal. In some cases, the shaped charging signal may be a signal of any shape, whether heating, charging, or discharging, that is not a constant DC signal, but does not conform to a traditional repetitive charging signal, such as a repetitive square wave or triangular wave charging signal.

The circuit of Figures 1-3 includes switching elements 112, 114 (considered to be part of circuit 110) that generate a controlled initial pulse train at node 136, which is then converted by filter 110 into a shaped signal to generate a signal to be applied to or from the battery, according to one embodiment. The switching elements can also be used to generate a discharge signal from the battery, with pulses similarly generated at node 136, without the presence of a charging current on rail 120.

As introduced above, the circuit 100 may include one or more components that shape a signal that intentionally causes heating of the battery 104 by a coordinated combination of charging and discharging. The circuit 100 may include a first switching element (e.g., transistor 112) and a second switching element (e.g., transistor 114), where the first switching element is connected to a power rail and thus a power supply 118 during charging and is coupled to a capacitor 122 on the rail during discharging. The capacitor may have various functions, including regulating the discharge signal, as discussed in more detail below. The first transistor 112 may receive an input signal, such as a pulse width modulated (PWM) control signal 130, that causes the first transistor 112 to operate as a switching element 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 with a drain node connected to the first inductor 140, a source connected to the rail, and a gate receiving the control signal 130 from the signal generator 110. Also, in various embodiments, the circuit 110 may include an inductor 140, as well as various other possible inductive elements. The circuit 110, and in particular the combination of the inductors 142, 140 and the capacitor 148, may be considered a boost topology when operating bidirectionally for both charging and discharging, the discharge portion of heating, or more generally, when controlling current from a battery in absorbing current to a load during normal operation, as described in more detail below.

During heating, the system may operate to both source current to the battery (commonly referred to as charging, although 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, although it is similarly recognized that during heating, the system optimizes the current from the battery for heating rather than powering the load). The system may control the heating sequence to transition rapidly between sourcing and sinking current from the battery. For sourcing (charging), the circuit controller 106 may provide a control signal 130 to control operation of the first transistor 112 as a switch that, when closed, connects the first inductor 140 to the rail 120 to allow current from the power source (and/or capacitor 122) to flow through the first inductor 140 (and second inductor 142, if present) to the battery. The second transistor 114 may receive a second input signal 132 and may be connected to the drain of the first transistor 112 at node 136. In some cases during charging situations, the second input signal 132 may be an inverse PWM signal to the first control signal 130 to the first transistor 112, with switching coordinated so that one is on and the other is off.

The inductance value or values, capacitance value or values, time and frequency of operating the transistors, and other factors can be adjusted to generate a waveform, particularly a waveform with controlled harmonics to the battery to heat the battery. With reference to the exemplary signals shown in Figures 4-6, the signal at node 136 when supplying current may be a pulse train of 0 volts to about rail voltage. The pulses at node 136 may vary in duty cycle and may be generated at varying frequencies. However, overall, the pulses are generated to provide a signal that is the same or nearly the same as the target current signal to the battery. Thus, a signal such as any of Figures 4-6 will be present at node 138 based on the combination of pulses present at node 136 (which are shaped at 138 by filter arrangement 110) at node 138. Depending on the signal, pulses of 10 seconds to 1000 seconds (or more) may be generated to create the desired charging signal.

In the discharge sequence, the upper first transistor 112 is initially turned off and the lower second transistor 114 is turned on. The second transistor may be blipped only long enough to initiate current flow from the battery to the inductors 142, 140. This transistor may be controlled to eliminate or minimize current flow through the second inductor to ground. When current (discharge) from the battery is initiated, the second transistor is turned off and the upper transistor 112 is turned on with the power supply off or on, driving current to the rail capacitor 122 and/or the load 144. When current flow from the battery is initiated, the discharge signal or the discharge portion of the signal may be similarly shaped by controlling the pulse at node 136. 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 on or off. When off, current is directed to the capacitor and/or load. When on, the power supply may include a feature that may regulate to maintain the rail voltage, and if discharging into the current causes the rail voltage to rise above a certain level, the power supply may be synchronized to maintain the set rail voltage.

Overall, the system may be controlled to transition rapidly between supplying and absorbing energy from the battery during heating. Additionally, the circuit may operate to shape the current to and/or from the battery by controlling the pulses at node 136. These features, alone or in various combinations, may allow the battery to be heated to a level sufficient for charging to occur. It is to be recognized that different types of batteries have different temperature thresholds for proper operation, including charging or load powering. Additionally or separately, heating may be performed with little or no charging to the battery, or alternatively, energy may be directed to optimal circuit efficiency using components with the multifunctional roles of heating, minimizing or avoiding electrode damage such as plating, transitioning to charging, changing the signal to one of optimal charging, and transitioning to prevent excessive heat generation, controlled heating and controlled charging, among other benefits.

As introduced above, the system may include a first capacitor 122 connected between the power rail and ground. The capacitor may be used to store discharge energy, which may then be used alone or in conjunction with power from the power source to power the load being charged. As discussed in more detail below, the capacitor 122 may also be useful for conditioning the discharge signal prior to further processing by power conversion or direct powering to the load. Also, 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 cases, when the system is providing current to the battery during heating, the discharge energy from the battery stored in the capacitor may be returned to the battery. The circuit may also include a second capacitor 148 connected to ground between the first inductor 140 and the second inductor 142. The second inductor 142 may be connected to the battery (e.g., the anode of the battery 104).

During charging or load powering from the battery after heating, the system may generally operate to prevent abrupt changes in the signal applied to or from the battery 104. In addition, during charging, the filter may convert the pulses at the input of the filter into a charging signal and may filter any unintended 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 may prevent abrupt increases in the current sent to the battery 104. Furthermore, the inductor 140 or the inductors 140 and 142 may shape the waveform applied to the battery, either alone or in combination with the capacitor 148, and the shaping of the waveform may be controllable by controlling the signal applied to the inductor. These components may be used to control the discharge waveform shape as well. In another example, the capacitor 148 may store energy from the power source while the first transistor 112 is closed. When the first transistor 112 opens in conjunction with closing the transistor 114, the capacitor 148 may provide a small amount of current to the battery 104 through the second inductor 142 to resist sudden drops in current to the battery, as well as be used to controllably shape the waveform applied to the battery to avoid sudden negative transitions during conventional charging, especially after heating. The filter circuit also removes other unwanted signals, such as noise, which may include relatively high frequency noise.

Of course, the system may include more or fewer components. For example, one or more components of a filter circuit may be removed or modified as needed to filter or regulate signals to and from the battery. Many other types of components and/or configurations of components may also be included in or associated with the system.

4-6 show exemplary possible heating waveforms. In each case, the controlled waveform transitions from a charging or supplying portion 410 (510, 610) to a discharging or absorbing portion 420 (520, 620). At a high level, the heating waveform in FIG. 4 appears as a sine wave, with the positive going portion of the waveform being the current to the battery (e.g., the current path to the battery in FIG. 1) and the negative going portion of the waveform being the current from the battery (e.g., the current path from the battery to the on-rail capacitor in FIG. 2 or FIG. 3 (but the current path through the lower transistor to ground is only for initiating 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 waveform to or from the battery.

The heating waveform in FIG. 5 is an asymmetrical sine wave, where 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 cases, especially with a fully or nearly fully discharged battery, it may be necessary to add slightly more energy than is being discharged to avoid over-discharging the battery. The heating waveform in FIG. 6, although controlled, has arbitrary shapes of the current to the battery compared to the current from the battery. Furthermore, these shapes are not consistent from one input current portion of arbitrary shape to the next input current portion of arbitrary shape, and from one output current portion of arbitrary shape to the next input current portion.

The frequency of transitions from supply to absorption, the shape of the supply vs. absorption signal, and other aspects of the heating sequence may vary. The shape of any portion of the signal, whether to or from the battery, may be based on the impedance of the battery relative to the signal being applied to or from the battery. The signal definition may be pre-defined. The signal definition may also be algorithmic depending on various battery parameters including SOC, temperature, cycle count, battery chemistry and composition, and many other possible attributes. The signal definition may also change during the heating and charging process. As described herein, impedance and harmonics may affect the selection or definition of the charging signal. As a general concept, a signal definition associated with a relatively high impedance and associated harmonics may be selected for a heating sequence having a relatively low impedance and associated harmonics for a discharge to power a charging or load sequence. Note that a relatively rapid change between supplying current to the battery and absorbing current from the battery may also be used for heating, and once a sufficient temperature is reached, the system transitions from absorbing current (when charging) so that the battery is not damaged by charging.

In a heating sequence, one or more attributes of the charging and/or discharging portions of the signal may be tailored to a relatively high impedance characteristic, as compared to a charging sequence, where the charging signal may be optimally tailored to a relatively low impedance characteristic. Current may be briefly injected into the cell and then briefly withdrawn from the cell to generate heat without initiating substantial battery charging. The frequency of transitions between current to and from the battery may affect optimal heating if the harmonics associated with the transitions are relatively high and the energy is primarily used for heating. Additionally or alternatively, the charging or discharging portions of the waveform may be defined to include harmonic attributes associated with a relatively high impedance. Thus, the current energy to or from the battery may be primarily dissipated as heat, due to the relatively high impedance (typically resistance), as opposed to charging a capacitor during charging, charging, and/or powering a load during discharging.

Battery temperature may be assessed in a variety of ways. In one example, the system may use a temperature sensor in the battery to assess the battery temperature. A variety of temperature sensors may be employed in contact with the battery, in contact with the terminals of the battery, disposed in a housing that contains the battery, etc. Various examples of sensors include thermistors, thermocouples, infrared sensors, diodes and transistors, or a myriad of different types of temperature sensors.

In another example, the use of harmonic or other frequency attribute battery responses may be used to determine 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 the battery's temperature, particularly the external temperature). The use of harmonic responses may also provide a more uniform assessment of the battery's ability to accept a charge.

In one embodiment, the system uses a characterization of the battery response to various harmonics at different temperatures. Any given battery type or specific battery may be characterized. The characterization may be stored in a look-up table in memory that may be accessed by the processor, such as by setting a threshold value. In this embodiment, it is understood that different battery chemistries and configurations result in different impedance responses at different temperatures. Thus, for a given battery, the impedance response of the signal with a particular harmonic frequency applied to the battery will vary depending on the temperature. In some cases, temperature probe signals at different discrete frequencies may be used to generate impedance responses, which may then be compared to the characterization to assess temperature, or more generally, the ability of the battery to accept a charge and therefore whether heating is required before charging can begin. The impedance response may be characterized by an imaginary component, a real component, or both the imaginary and real components of the impedance. In some embodiments, the impedance response may be used alone or in combination with a sensed measurement of the battery temperature to determine whether the battery should be heated or can be charged. Similarly, other frequency-based responses or impedance-derived terms such as susceptance, admittance, and capacitance may be used alone or in place of direct sensed temperature measurements to determine if the system is configured to heat the battery.

In general, in various embodiments where impedance values are considered, the technique evaluates harmonic values whose values are associated with some impedance, either alone or in combination. Given the roughly inverse relationship, the term impedance as used herein includes its inverse admittance, and may include its components, conductance and susceptance, either alone or in combination.

In another aspect, heating of the battery may be achieved by controllably charging or discharging the battery, or a combination thereof, as described above. In this example, the signal, whether a charging signal, a discharging signal, or a signal that alternates between charging (supplying current to the battery) and discharging (absorbing current from the battery), is composed of one or more harmonics that are adjusted to optimize the relatively high conductance and relatively high reactance of the battery. Using a charging signal as an example, the optimized combination (or balance) between high conductance and high reactance results in heating in the battery. In this example, the signal is composed of harmonics that can be identified in one or more frequency domain representations (or transforms) of the signal. The adjusted signal may also be shaped to reflect various harmonic attributes. In a very simple example, the signal may be composed of discrete sine waves at a particular frequency so that it is composed of harmonics and shaped in a harmonic form. In general, if the conductance is very high but the reactance is too low, it may generate enough heat to produce a larger signal than many charging environments can support. Similarly, if the conductance is too low, even if the reactance is high, too much energy will be converted to heat. So, for any given starting temperature and battery chemistry, the system selects a charging signal containing harmonics that balances high conductance and high reactance.

In one embodiment, a battery of a given configuration may 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 may also determine when the heating signal is applied to reach a sufficient state to initiate heating. The balance may further consider attributes that minimize the energy used for actual charging, which is instead applied to heating. This technique may be applied to generate harmonics of the discharge signal, which may be the same or different as the charge signal at various temperatures.

The frequency of the harmonics may typically be relatively higher than the kinetic and diffusion processes in any given battery for which the signal is optimized. In general, a frequency faster than the dynamic response of the electrochemical processes is selected so that the magnitude of the voltage and current does not adversely affect the electrodes or interfaces of the battery when heating occurs. Thus, a relatively high voltage signal that would normally cause plating (e.g., 6V, where a maximum of about 4V is typically specified) may be used for heating, but plating will not occur at this relatively high voltage because the signal is composed of a harmonic or series of harmonics faster than the kinetic rate. That said, in many instances, a signal is selected that falls within a specific charging (or discharging) voltage level that is relatively low. Also, in accordance with the various heating techniques described herein, the system is optimized in some cases to heat without net charging. In such cases, the system controls the charging and discharging signals so that the signals cancel each other out with a relatively uniform total energy by taking into account the difference in the energy conversion efficiency difference between the charging and discharging portions at any given temperature.

Figure 7 shows an example of a profile for heating a battery to a battery temperature at which charging is possible. In this example, the initial battery temperature is -20°C at 10% SOC. The battery may be heated until it reaches approximately -15°C, at which point charging can begin. It can be seen that even if the battery warms up by approximately 5°C before charging begins, the SOC remains at approximately 10%. It can also be seen that the battery temperature continues to rise until it reaches 100% SOC.

In many conventional battery powered systems, the system relies on a DC discharge current from a battery to power some load. The battery may be a single cell or a small number of cells, such as in a power tool, vacuum cleaner, portable speaker system, or a large pack of interconnected cells, such as those found in some electric vehicles. The cell configuration and type will typically depend, at least in part, on the capacity specified for the system in which the battery is operating, the discharge current required by the system's load, and other factors. Nevertheless, conventional batteries provide a DC discharge current to power a load. When an AC signal is required to drive a load, such as an AC motor, a converter, such as converter 146, is used to convert the DC output of the battery to the AC signal required by the load.

For controlling the heating of the battery and the charging based on the heating, and defining the shape of the harmonically adjusted charging signal during or after heating, etc., aspects of the present disclosure include a unique battery charging and heating sequence based on the starting temperature and the expected temperature change of the battery during charging. Aspects of the present disclosure further include techniques for shaping the charging signal for 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 a sinusoidal frequency and may have a corresponding shape. Aspects of the present disclosure further include a method for determining a maximum charging current that can be applied based on the current state of the battery, alone or in conjunction with one or both of the heating sequence and the shaped charging signal, and that takes into account the battery heating and/or battery temperature.

In one aspect, the charging system is configured to evaluate the battery temperature and determine the charging sequence based thereon. As mentioned above, in some situations, the temperature of the battery may be below some threshold where charging may damage the battery or may simply be ineffective. In such a situation, the system may generate a signal to warm the battery. As mentioned above, various possible warming signals are possible. Once the battery temperature exceeds a threshold, the system may begin charging the battery while continuing to warm the battery. Finally, once a second threshold is exceeded, the system may stop warming and transition to a signal intended only for charging the battery, although it is recognized that batteries tend to warm up when they are charged. An advantage of the harmonic regulated charging signal is that it optimizes the energy usage for charging, thereby causing less heating compared to various conventional charging techniques. This may allow for more current to be delivered during charging than conventional systems, due to less heat generation, among other advantages.

Turning now to specific methods of heating the battery, FIG. 8 is a flow diagram showing one possible example of a method of heating a battery, and FIGS. 9A and 9B show possible examples of combined charging and heating signals. The magnitude of the current of the signals in FIGS. 9A and 9B will depend on the cell capacity and the external temperature. For example, for some cell types, the current will be about 6A-12A peak-to-peak for a 3 or 4 Ah cell. In some cases, a larger current is possible for heating, allowing the battery to heat up faster (compared to a smaller signal). Currents larger than those specified for charging are also possible, and potentially could be relatively large (e.g., signals of currents of 60 App or more), since a heating frequency can be selected that does not affect the electrochemical process.

Referring to FIG. 8, the charging system first 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 in or located on the battery (or, in the case of a battery pack, more than one temperature sensor may be used). The system may also obtain the ambient (environmental) temperature in addition to the battery temperature. It is to be appreciated that the battery temperature may be sensed as well as calculated from other information.

Depending on the type of battery, the system may recognize a first temperature T1 below which the battery should be heated prior to charging, and a range of possible temperatures between a relatively low first temperature T1 and a relatively high upper second temperature T2 above which the system may begin charging and continue heating, above which heating is no longer necessary and the system may charge without continuing the intended heating. By way of example, the method and system are discussed with useful reference to three temperature zones: below T1, between T1 and T2, and above T2, but it will be recognized that there may be more or fewer zones and that the various heating and charging operations may be modified accordingly. For example, the intermediate zone may be divided into sub-zones that transition from substantially more to less heating and substantially less to more charging as the entire system transitions from a first state in which the system is only heating to a third state in which the system is only charging. Regardless of the division into intermediate zones or sub-zones of states, in the intermediate stages, the system may charge at a slower rate than in the final stages, where the battery is brought up to a temperature where charging can proceed without additional heating. Nevertheless, in one embodiment, the system determines the mode to start (heating, hybrid heating and charging, or charging) from the obtained temperature T of the battery (operation 802).

In the first mode (operation 904), when the temperature is too low for charging (e.g., T is equal to or lower than T1), the system accesses a signal used for heating only. Examples of such signals are discussed with reference to FIGS. 4-6 by way of example, but may be provided by circuits such as those shown in FIGS. 1-3. In one specific embodiment, the heating signal is a sinusoidal current waveform as shown generally in FIG. 4. The current waveform alternates between positive and negative currents 410 and 420 of the sinusoid centered around zero current. The frequency of the sinusoid may be selected through battery characterization and testing based on the type of battery. The purpose of the sinusoidal shape centered around zero current, or (in the case of other shapes) the alternating heating waveform when the temperature is deemed too low to charge without potentially damaging the cells, is to initially heat the battery without significant net charging, among other things mentioned above.

The method is discussed in terms of starting in a first mode (operation 804), checking the temperature, and then proceeding to a second mode and then a third mode based on the battery temperature. It is to be appreciated that the method may start in either the second or third mode depending on the starting temperature. Also, in some configurations, the heating sequence may be initiated for a period of time as opposed to the battery reaching a certain temperature (e.g., T1 or T2). Thus, for example, if the initial temperature is below T1, the system may initiate the heating sequence for a period of time and then transition to Hybrid Mode 2, described below, or to Full Charge Mode 3 in an embodiment without an intermediate mode or when timing is configured without an intermediate mode. It should be noted that other thresholds besides battery temperature (e.g., time or current applied, time at ambient temperature, modeling, and combinations thereof) are possible. Similarly, while the method is primarily discussed with respect to reaching different threshold temperatures T1 and T2, the system may operate when the temperatures are reached, when the temperatures reach a range therearound, etc.

It is to be appreciated that other heating signals may be used in the first mode. In situations where the charging sequence is first initiated when the temperature is below T1, and thus the heating mode is first initiated as a function of temperature, it may be possible to transition from a sine wave centered around zero to a sine wave with a positive DC offset to initiate some charging, or to start with a sine wave with a positive DC offset or a sine wave with more positive charging energy as in the signal of FIG. 5. The signal may then transition to the second mode, described below, when the battery reaches temperature T1 and warms up beyond T1 or even a second temperature at which the system transitions to a full charging sequence.

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 range (e.g., T is between temperature T1 and temperature T2), the system may use a mixed charging signal, examples of which are shown in FIGS. 9A and 9B. The mixed charging signal may include charging portions 902, 904 and heating portions 906, 908. These examples show a repeating pattern of a charging portion followed by a heating portion. However, the mixed signal may include any sequence of charging and heating portions. For example, the mixed charging signal may include a sequence of several charging portions (e.g., 902 or 904) followed by a heating portion (e.g., 906 or 908) followed by a subsequent sequence of heating portions. In such an example, each charging portion begins at the end of the proceeding charging portion. Similarly, the length of the charging and heating portions may vary. For example, near temperature T1, the heating portion may be relatively longer than the charging portion, whereas near temperature T2, the charging portion may be relatively longer than the heating portion (or a series of charging portions (with intervening rest periods) may occur before the heating portion), or some heating portions may be replaced by rest periods, as discussed below and elsewhere herein. In the example of FIG. 9A and FIG. 9B, the rest period includes a transition 918 (920) from a charging portion 914 (916) to a rest period (occurring at the heating portion 906 or 908) with no (or substantially no) charging or discharging current, followed by a transition to another charging portion 902 or 904. Similarly, the composite signal may have a relatively low charging energy near temperature T1 and a relatively high charging energy near temperature T2. Similarly, the composite signal may dynamically or programmatically change as the temperature increases between temperatures T1 and T2. Similarly, the definition of the signal may depend on the onset temperature, such as where the onset temperature is somewhere in the range T1 to T2.

In the illustrated example, the charging portion 902, 904 of the hybrid charging and heating signal has a sinusoidal, or more generally, shaped, non-abrupt leading edge 910, 912 followed by a body portion 914, 916 that terminates at a trailing edge 918, 920. In many examples, the leading edge (e.g., leading edge 910 or 912) does not need to be a very high frequency abrupt edge, such as a square wave, to avoid injecting high frequency harmonics into the battery when the charging portion of the signal begins. With reference to FIG. 9A, the heating portion 906 exists between the charging portions and is defined by a sinusoidal heating signal centered at about zero amperes. Thus, the sine wave oscillates between positive (charging) and negative (discharging) currents. In some examples, the heating signal has a net capacitance difference of about zero, such that the energy in the heating portion of the hybrid signal is primarily toward heating, and the net energy to charge or discharge the cell is near zero or zero. The heating portion of the charging signal shown in FIG. 9B has a DC offset, which is discussed in more detail below.

In various possible examples, the frequency of the sinusoidal heating portion of the composite signal or the heating limited signal (discussed above) may range from 1 KHz to 100 KHz. The frequency may also range below 1 KHz (such as in the range of 100 Hz to 1 KHz) depending on the cell and the particular conditions. Similarly, frequencies above 100 KHz are possible in some circumstances. In one specific example of a 3000 mAh lithium-ion rechargeable cell with a maximum discharge current specified at 35 A for conventional CCCV charging and a current specified at 4 A at 4.2 V, the heating sine wave may be 10 KHz and cycle from -10 A to 10 A (for such a cell, temperature T1 is approximately -10° C. and the cell temperature may reach 5° C. at T2). Heating as described in this and other examples herein results in the maximum possible internal heating due to contributions from resistance and susceptance mechanisms. The susceptance from the coiled electrode creates a magnetic field that is absorbed by the magnetic element of the cathode and may contribute to heating in parallel with I ² R heating through the current collector. It is to be appreciated that such relatively large currents are not typically specified at relatively low temperatures. For example, for the same type of cell, conventional charging (if possible) would be on the order of about 2 A. However, as noted above, the energy of the heating portion of the signal is primarily directed toward heating, allowing for larger currents than charging alone. The frequency and positive and negative current values of the heating signal will depend on the type of battery, the capabilities of the charging circuit, the capabilities of the power supply, and other factors. The sinusoidal heating signal may be positive and negative symmetric (e.g., cycling from +10 A to -10 A), but it is also possible to have an asymmetric signal. It is also possible to have a sine wave centered with a positive DC offset (e.g., as shown in FIG. 9B) so that there is a net charge in the heating portion, or to transition from a zero-centered sine wave to some non-zero positive offset sine wave so that the battery warms up in temperature zones T1-T2. It is also possible to operate mode 2 for a set period of time, or to operate a sequential combination of modes 1 and 2 for a set period of time, transitioning from the first mode to the second mode based on time. Other thresholds may be used to transition between signals, such as time and temperature, or using other measurements such as ambient temperature, net current into the battery, or voltage as a surrogate for temperature.

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

In some examples, the heating signal may be applied to maintain the battery in some operable range. The signal may be applied when the battery temperature falls below a temperature threshold, even if the battery is fully charged. A frequency may be selected where no net charge is applied to the battery, so that heating may be maintained without exceeding an upper charge threshold. Alternatively or additionally, the system may charge and discharge the battery in a small window (e.g., 99%-100% percent) while generating the heating signal to maintain the battery temperature. In various examples, when connected to a charger, the system may maintain the battery temperature in an optimal range for powering some loads and not fall below a threshold where the battery is operable when the battery is in a cold ambient environment where it may otherwise cool below an optimal operating temperature range.

For various modes and more, various heating signals, hybrid charging/heating signals, and charging signals can be generated using the circuits shown in Figures 1-3 and others.

As described herein, the charging signal or hybrid charging and heating signal may include a shaped leading edge, a body portion, and a dwell period, which may include a heating sine wave overlay. The charging technique and charging signal described is not a conventional constant current, constant voltage type charging where a specified constant charging current is essentially applied until the battery voltage begins to rise and the charging current is reduced. Nor is the charging technique pulsed charging, since the charging signal defines a specifically shaped leading edge. Indeed, high frequency harmonic content square pulses are typically avoided for charging due to the high impedance, at least at the initial initiation of the pulse, to uncontrolled high frequency harmonic content square pulses.

Referring to FIG. 11, a method for generating a shape of the charging portion of a signal (e.g., a hybrid charging/heating signal or a charging signal) includes obtaining an impedance spectrum of a battery, selecting a frequency from the impedance spectrum where the impedance is relatively low, and using that frequency to define a shaped leading edge of the charging portion of the signal. In one example, the system uses or references an imaginary impedance (reactance) value. The shaped leading edge and the entire signal can be generated using the circuits shown in FIGS. 1-3 and others.

To obtain the impedance spectrum, in one possible example, the method includes applying a probe signal to the battery (operation 1102). The probe signal may include a series of harmonics that the system may use to evaluate the impedance of the battery for various harmonics. The probe signal may be a charging signal or a dedicated signal. The probe signal may be interleaved during charging, or may be discrete at the beginning of charging, intermittent or periodic during charging, etc. In one example, the probe signal may be a square wave or a square pulse. In one specific example, the probe signal is a square wave centered at zero amperes. In one possible example, the probe signal is a square wave centered at zero amperes and has a +4V (positive) portion and a -4V (negative) portion, where the average current is 0A. The duty cycle is 50%. The frequency, duty cycle, current or voltage magnitude, or other attributes of the probe signal may vary depending on the cell type, device type, temperature, state of charge, and other possible parameters. These parameters may be determined based on the characterization of any given cell type. In one embodiment, a square wave probe is applied to the battery for a single time period of about 30 milliseconds. In other words, the probe signal may include positive and negative square pulses of a current. The pulses may have the same pulse duration (e.g., 15 milliseconds each) or may have different durations. The probe signal may include only positive pulses (charging the battery) or only negative pulses (discharging current from the battery). Each pulse may include the same magnitude of current or may be asymmetric. Although other probe signals are possible, a square pulse or square wave has harmonic content of a wide range of frequencies and can be efficiently generated by a variety of conventional charging hardware topologies. In general, the purpose of the probe signal is to very simply and discretely introduce a wide range of harmonic content into the battery in order to evaluate the impedance of the battery to various harmonics. Thus, the probe signal, whether a square wave or square pulse or other signal, is intended to introduce a series of harmonics into the battery in an instant. For a square wave centered at zero amps, the current to and from the battery can be equal in magnitude with little or no net charging effect. The idea is to probe the cell without changing the state of charge. In situations where changing the SOC is acceptable (e.g., charging at less than 100% SOC and in moderate temperature conditions), some net charging is possible and acceptable. Also, negligible net charging from the probe signal is acceptable as well, provided the probe is not frequent and the net charging is negligible. In some configurations, a wide range of different probes with different harmonic content can be injected. Even though uncontrolled and/or high frequency harmonics can have a detrimental effect on the battery, the system applies square pulses for only very short durations to obtain the impedance spectrum, substantially avoiding such effects.

In the presence of the probe signal, the system measures the current and voltage at the battery terminals (operation 1104). The current and voltage signals are acquired in the time domain. For each current and voltage measured in the presence of the probe signal, the system obtains a frequency spectrum (operation 1106) that may further generate an impedance spectrum. In one example, the system generates a domain transform of the current and voltage signals to generate a voltage frequency spectrum and a current frequency spectrum. The domain transform may be a discrete wavelet transform using a Morlet wavelet. In some cases, the wavelet may be considered a Gabor wavelet or a complex Morlet wavelet. In one possible implementation, the system may generate the impedance spectrum using fixed-point arithmetic, which allows the use of a relatively low-cost and simpler microcontroller or other computer platform, which is more common in charging environments that do not require or are not traditionally available with significant additional computing power.

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 impedance at various frequencies is generated by dividing complex voltage values at various frequencies by complex current values at the same frequencies. This generates 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).

Notwithstanding the above techniques, the system generates an impedance spectrum that identifies the battery's impedance for specific frequencies of harmonics of the signal applied to the battery. Thus, in a simple example, a square pulse probe signal applied to a battery will have many harmonics present. With the techniques discussed herein, the system generates a discrete impedance of the battery for some or all of the discrete harmonics in the probe signal. This spectrum, at a generalized level, indicates the battery's resistance for a specific frequency of the charging signal. The battery may have a greater or lesser impedance (or, more generally, resistance) for various frequency harmonics of the probe signal.

The system may identify from the impedance spectrum a particular harmonic to be used to define the leading edge of the charging portion of the signal (operation 1108). To determine the shape of the leading edge of the charging signal, the system determines an optimal frequency from the impedance spectrum generated by the probe signal. In one particular example, the optimal frequency is the frequency associated with the lowest impedance (specifically, reactance in some embodiments) in the impedance spectrum. Thus, the system selects the frequency associated with the lowest impedance. Of course, there may be moments when the system may alternatively 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 in the shape of a frequency associated with a lower impedance will transfer energy for charging more efficiently compared to a frequency associated with a higher impedance. The optimal frequency is then set as the leading edge of the charging portion of the charging signal or composite signal. Thus, the leading edge 1010 defines a portion of a sine wave at the identified frequency, as shown in the examples of FIGS. 10A and 10B.

In addition to the shape of the leading edge of the charging portion, the system also determines overall attributes of the signal, including the length of time of the dwell period relative to the charging time (including the shaped portion and the body portion), the total duration of the signal, and other attributes. In one possible example, the duration of the charging signal and the dwell period are preset based on the battery characterization. The duration of the charging signal includes the shaped leading edge and the body portion following the shaped leading edge. In various possible examples, the charging portion may be in the range of 100 microseconds to 10 milliseconds. The total duration includes the charging portion and the dwell period (or heating portion). The dwell period (or heating portion) may be in the range of 100 microseconds to 10 microseconds. In other possible examples, the duration may be in the range of 100 microseconds to 10 milliseconds. The peak current at the peak of the shaped leading edge and the body portion of the charging portion of the cell may be around 20A, but the peak current value may vary significantly from the exemplary peak current depending on the cell type, temperature, characterization, and other factors. An example of determining the charging current, including the peak current, is discussed below.

The method of determining the leading edge shape may be repeated periodically, intermittently, throughout the heating or charging cycle to reach various targets (such as SOC) or otherwise. In one embodiment, the probe signal and subsequent operations (1104-1110) are repeated approximately every 1/2% to 1% change in SOC. In another example, the probe signal and subsequent operations are performed over time (e.g., every 5 seconds, 30 seconds, or 60 seconds). The frequency of the probe signal and subsequent operations may change over time. For example, the cell changes faster when heating, so the speed of the probe, etc. may change. As the cell approaches full charge, the speed of the probe may also change.

Aspects of the present disclosure also include a method of generating a current level for a charging signal, where the current level is set such that the battery does not overheat during the course of a charging cycle. This method may be adapted for use in conjunction with the techniques described herein, such as by setting the current level of a shaped hybrid charging/heating signal or a shaped charging signal. This method may also be used to set the current level of any form of charging signal, alone or in combination, to account for battery heating that occurs during charging in various charging situations and to prevent the battery from overheating during charging, among other advantages.

12, the method 1200 begins with accessing the battery temperature and the ambient temperature (operation 1202). The technique may take into account the battery temperature and the ambient temperature, or may take into account only the battery temperature, or may take into account other parameters. As described herein, the battery temperature may be obtained, or more generally, may be 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 being charged. The ambient temperature may also be accessed from a third party device (e.g., some form of temperature sensor in proximity to the device being charged) with a temperature signal available via some signal (e.g., Bluetooth or Wi-Fi). In some configurations, the ambient temperature may be obtained over a network connection, such as from a third party service accessible over a network connection. In any event, the system may have access to one or both of the battery temperature and the ambient temperature. The system may also have access to a forecast 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 that will remain below a maximum threshold temperature during charging if the battery is charged at or below that maximum current. The maximum threshold temperature may be, for example, a specified maximum temperature above which charging will be stopped. The maximum threshold temperature may also be some other specified maximum temperature that the system will not exceed.

The maximum current may take into account the state of charge and identify a charging current that, when applied to the battery, does not heat the battery above a maximum threshold temperature at the end of the charging cycle. Thus, for example, at the same temperature, the maximum current may be higher for a relatively higher starting state of charge compared to a relatively lower maximum current for 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 that includes battery temperature variables and ambient temperature variables). The model may also be a look-up table that receives battery temperature and ambient temperature values as keys and identifies a charging current value based on these keys. The model may be based on battery characterization, which in one example identifies the temperature profile of the battery over a range of charging conditions and how these charging conditions affect the battery temperature.

In response to the battery temperature and the ambient temperature, the model generates a maximum value for the charging current. In one example, the model may estimate a fully discharged state, where the identified charging current value represents the current at which the battery will be charged to a fully charged state and will not exceed the maximum threshold temperature. The system then accepts this state of charge and generates a current value at which the battery will be fully charged without exceeding the threshold temperature. In such an example, the current value may be slightly larger than for a fully discharged state. As an advantage of the technique not considering the state of charge, the system may operate with a default current that does not exceed the temperature threshold and does not require access to an ongoing accurate state of charge evaluation. This may be beneficial in various situations, such as when the battery is first being charged and the current or accurate SOC is not available.

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

It should be noted that the maximum current, or any other current value, may be limited by the capabilities of the charging environment. Thus, the system may access a charging limit based on the charging environment (operation 1206). In some cases, the charging hardware itself may be limited as to the amount of charging current it can provide. For example, the system may be able to charge from a higher current source, while connected to a lower current source, limiting the maximum charging current the system may provide. In other examples, other limitations may be imposed on the system that determine the current limit available for charging the battery. For example, the charging hardware may be limited based on the limitations of the power source. Nevertheless, the system may take into account the system-based current limit. This is relevant when the maximum current from operation 1204 exceeds the system current limit, which is effectively the maximum current.

Finally, the system may access a third current parameter that is associated with the amount (e.g., maximum amount) of charging current to the battery based on the current temperature of the battery. As described herein, a battery below a certain temperature threshold may not be charged at the same rate as above this threshold or threshold range. As the battery warms up, more charging current becomes available. Characterization of any given battery type may identify the maximum current that may be applied based on its temperature without damaging the battery. As described herein, temperature affects the battery's ability to receive a charge. In this example, the system accesses a model that determines the current maximum current based on the current battery temperature. Where the current limit described above identifies the maximum current that may be applied to keep the battery 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 is currently acceptable based on the current temperature of the battery. This value may change as the battery warms up. Also, if the value is below a threshold (e.g., T<T1 described above), the model indicates that no charging current will be applied until the battery reaches or exceeds the threshold.

To summarize the above, as an example, the system can identify three maximum current limits: (1) a first current limit that is the maximum current to which the battery can be charged given the battery temperature and the ambient temperature, but not exceeding a certain temperature in the future; (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.

The system then selects the smallest of the three generated current limits. Here, for example, at a relatively low battery temperature and in a cold environment, the first current limit may be relatively higher than the third current limit. This is because the battery cannot initially accept a maximum charge at a low temperature and the battery temperature does not rise as high as in a relatively warm ambient environment due to the relatively low ambient temperature. Thus, the system selects the third charge limit because charging at the relatively high first current limit would exceed the third current limit. However, as the battery warms up, the third current limit may rise to a level above 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 will select a current that allows for instantaneous fast charging but will not cause the battery to overheat later in the charging cycle. In either or any situation, if the maximum current from the system is less than one or both of the first and third limits, the system will use the second current limit since it cannot provide a higher first or third limit.

As described above, when in either the hybrid heating and charging mode or the charging only mode, the system applies a complex shaped charging signal having a charging portion and a heating portion or a resting portion, either or both of which may include a positive offset such that some charging current is shifted in either the heating portion or the charging portion. Maximum charging current values may be translated into various portions of the complex charging signal.

In one particular example, the maximum charging current is the average value of the entire 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) as well as other parameters of the charging signal, such as the total period and the rest period (which may be understood as 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 discussed above, in determining the shape of the charging portion, the system may have access to time parameters of the entire signal, such as the total period and the rest period of the signal. With this information, the system can determine the time of the charging portion (shape and body) of the signal.

In one possible example, the system uses a current limit (average current) to set the peak current of the main body of the signal, taking into account the charge transfer that occurs at the shaped leading edge. For comparison, if the system selects a very high frequency harmonic for the shaped leading edge that may appear as a conventional square wave, sets the current limit to 5A, and determines a 50% duty cycle (50% for the charging and main body combined, 50% for the resting portion), the peak current of the charging portion will be 10A. However, the system will generate a relatively low frequency harmonic as the shaped leading edge (rather than the high frequency sharp leading edge of a square wave) in the case of a hybrid charging and heating signal or a charging signal, since such charging energy is transferred not only at the shaped leading edge but also in the main body of the charge. In the same example of a 50% duty cycle, if the average current is set to 5A, the peak current at the shaped leading edge and the upper part of the main body will be greater than 10A, since some charge is transferred at the shaped leading edge of the charging portion and the rest is transferred in the main body of the charge. In such an example, the system considers both the shaped leading edge and the body to be within 50% so that the shaped leading edge transfers less energy compared to a conventional square pulse, and the body peak current is higher than 10 A. Therefore, the system considers the charge transferred in the shaping and body portions of the charge portion of the signal in determining the peak current.

In nearly all instances, the peak current will be greater than the maximum current selected by operations 1204-1209. In some cases, the system may determine a peak current greater than the current that may be provided by the system's hardware. In such instances, the system may generate a positive charging current offset for the rest period such that the average current may be reached over the entire period of the signal (charging portion and rest portion). In other instances, the system may adjust the total period such that the charging portion becomes larger and the average current may be reached over a period of the signal by lengthening the time that the charging signal portion delivers charging current while the rest period remains the same. In another instance, the system may maintain the total period while shortening the rest period.

According to various aspects of the present disclosure, a system may include a controlled discharge signal from a battery, whether as part of a heating sequence or to power a load, including various possible harmonics (e.g., harmonic content at a specified frequency or a shaped discharge signal). Referring again to FIGS. 1-3, and also to FIG. 13, the system may include a battery 104 (1304) and a controller 100 (1300) that manages the battery discharge signal alone or in combination with a charging signal in the context of heating, while the discharge control may provide optimal discharge of the battery in the general operation of a battery-powered system. 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 as a battery management system. Notwithstanding this control arrangement, the system as a whole provides a discharge signal that may, in various possible examples, be tuned to one or more of the leading edge of the signal, other aspects of the edge of the signal, the harmonics that make up the body of the signal, and/or the trailing edge of the signal for a particular frequency that results in suppression and/or minimization of the impedance attributes of the battery in the presence of the discharge signal during operation of the system, or may be tuned to allow the battery to transition to charging or powering a load with initial heating. Nevertheless, the harmonic content of the discharge signal is controlled, and more generally, the discharge signal has non-conventional, non-DC attributes. The one or more harmonic components may be selected and controlled based on an evaluation of the attributes of the battery in the presence of the complex impedance or discharge harmonics to select and minimize impedance attributes (e.g., complex impedance) in the presence of the discharge signal when powering a load, to generate harmonics with relatively high impedance so that energy is primarily consumed as heat in a heating mode of operation, or other harmonic attributes may be controlled for various possible reasons. Controlling the discharge in this manner has several possible advantages for the battery over similar batteries discharged using conventional techniques, including optimized heating during discharge, extended battery life and increased capacity, increased discharge current, and other advantages.

However, in such a harmonic controlled discharge signal environment, conventional downstream systems are likely not suitable for receiving such a discharge control signal from the battery. Thus, in one example, a discharge signal conditioning element 1302 is disposed between the battery 1304 and the load 1306 (144) or incorporated into the load. The discharge signal conditioning element serves to condition the non-conventional discharge signal suitable for the load or an element that powers the load with energy from the battery. In one example, referring to FIG. 1, the discharge signal conditioning element is a suitable capacitor 122 or capacitor bank, or other energy storage element, that receives the discharge signal from the battery and is arranged to store sufficient energy for the load. Also, in one example, the load system 1306 may include a DC-AC converter or other form of power conversion 146 (FIG. 1) for powering the load, with the capacitor or capacitor bank being disposed between the battery and the DC-AC conversion component of the load system. The harmonic controlled discharge signal then charges a capacitor bank, which provides the DC power required by the DC-AC converter or directly by the load. The capacitor bank is sized and positioned according to the power demand of the load.

In another example, the load is configured to receive a harmonically adjusted discharge signal from the battery. For example, in the case of a DC powered load, the load may include a capacitor 122 at the input to the load that removes harmonic content from the discharge signal, as in the embodiment described above. In another example, the discharge signal may be controlled by a buck or boost circuit that drives the load. In such an example, the buck or boost circuit may be controlled to adjust the harmonic content of the discharge signal while simultaneously adjusting the discharge signal to the load. Although the signal conditioning elements and the load system are shown as separate blocks, the signal conditioning may be integrated with the load system.

In some cases, a heating waveform, particularly a sinusoidal heating waveform, may be set at a frequency and may include frequency attributes based on a combination of real and imaginary components of impedance. In particular, with respect to admittance, the frequency of the heating waveform may be based on real admittance (conductance) and imaginary admittance (susceptance) responses. It will be understood that while this discussion is presented in the context of admittance, specifically conductance and susceptance, it may also apply to resistance (the inverse of conductance) and reactance (the inverse of susceptance).

14A illustrates a real admittance (conductance) response 1400 over a range of frequencies for a sinusoidal signal applied to an exemplary lithium-ion cell at 50% state of charge. As shown in FIG. 14A, it can be seen that from frequency A to 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, and continues to decrease for frequencies above frequency B. In the illustration, frequency A is at an inflection point 1402 in the conductance response curve, where conductance increases with increasing frequency up to frequency A, and then begins to decrease for frequencies above frequency A. Also, in the illustrated example, the conductance is maximum at frequency A.

Referring to FIG. 14B, from near frequency A up to higher frequency B, for the same representative lithium ion cell at 50% SOC, the susceptance varies from a relatively small first susceptance value to a maximum peak susceptance value at frequency B. In the illustration, frequency B is at an inflection point 1402 in the susceptance response curve, where the susceptance increases with increasing frequency up to frequency B, after which it begins to decrease for frequencies above frequency B.

In various possible examples, the sinusoidal frequency of the heating signal described above in various embodiments may be established based on the conductance response, the susceptance response, or a combination of both responses. As noted above, admittance is discussed with the understanding that it also applies to the inverse values of resistance and reactance.

In one possible example, the heating frequency may be set as a value between the frequency at which the conductance peaks (e.g., frequency A) and the frequency at which the susceptance peaks (e.g., frequency B). In another aspect, the heating frequency may be set at a frequency value between the inflection point frequency of the battery's conductance response and the inflection point frequency of the battery's susceptance response. In the frequency zone between A and B, the conductance decreases relatively rapidly and the susceptance increases relatively rapidly. The heating frequency may be selected from a value in the frequency zone between A and B.

In a more specific example, the frequency of the heating signal lies in a range about the midpoint between frequency A and frequency B (e.g., frequency X). With reference to Figures 14A and 14B, the conductance peaks at about ¹⁰ Hz and the susceptance peaks at about ¹⁰ Hz. With particular reference to this, it can be seen that the conductance peaks at frequencies less than ¹⁰ Hz and the susceptance peaks at frequencies less than ¹⁰ Hz, where the term "about" represents the fact that the precise scale of the graph is not of a granularity to specify exact frequencies, but instead the figures are used to show approximate characteristics of the conductance and susceptance curves. Nevertheless, in this example, the heating frequency is selected at frequency X, which is approximately halfway between frequency A and frequency B.

From an electrochemical and electrodynamic point of view, at frequency A, the total distance traveled by electrons in the cell during charging can be large, facilitating the cancellation of charges in the applied electric field. As a result, there may be no other materials in the cell that exhibit polarizability, and the cell cannot support the high susceptance required for more uniform and multicomponent charge propagation and electron transfer. At frequency B, susceptance and polarizability are at their highest, while electron transfer is greatly reduced, and therefore I ² R heating of the current collector is also reduced. At frequencies between A and B, such as X, the conductivity and I ² R heating remain high, while the susceptance is much higher than at frequency "A," indicating that additional components and electrode area are involved in the heating. The susceptance is known to be due to the coiling of the electrodes in a cylindrical cell, and can be assumed to be relatively uniform throughout the cell. Also, frequencies in the selected range can be sufficiently removed from the time constants associated with chemical, electrochemical, and possibly electrokinetic mechanisms, thus avoiding nucleation and SEI growth during heating.

The frequency zone between the conductance maximum (inflection point) and the susceptance maximum (inflection point) defines an area within which a frequency that balances these problems and benefits may be selected. This frequency zone may also be based solely on either conductance or susceptance. For example, in identifying a maximum at a conductance inflection point, a frequency within some range of the frequency at the inflection point may be selected. In a more detailed example, this frequency may be higher than the frequency at the inflection point. The degree to which the frequency is higher may be set by some fixed offset, based on some difference (e.g., a percentage) below the conductance value at the inflection point, or otherwise. For susceptance, in identifying a maximum at a susceptance inflection point, a frequency within some range of the frequency at the inflection point may be selected. In a more detailed example, this frequency may be lower than the frequency at the inflection point. The degree to which the frequency is lower may be set by some fixed offset, may be based on some difference (e.g., a percentage) below the susceptance value at the inflection point, or may be otherwise. Also, for conductance or susceptance, the heating frequency may be selected based on the conductance or susceptance minimum, choosing a frequency lower than the conductance minimum or higher than the susceptance minimum. In Figures 14A and 14B, the susceptance minimum is the same frequency (slightly lower) as the conductance maximum 1402.

The term "about" will be understood by those of skill in the art and will vary to some extent depending on the context of its use. When used herein to refer to values of frequency, temperature, current, and the like, the term "about" is intended to encompass ±10% (including ±5%, ±1%, and ±0.1%) variations from the specified value as such variations are appropriate in the practice of the disclosed methods.

In the various examples above, including the discussion of Figures 14A and 14B, the heating frequency may be selected based on a variety of criteria. In some examples, the frequency may be based on an inflection point, a midpoint, or some other criteria, with it being recognized that there is some flexibility as to the exact number selected. Thus, for example, a frequency referenced to an inflection point may be at or near the inflection point, meaning that it may be within 10% of the value, or any other percentage value as previously mentioned. Similarly, in the case of a midpoint between two frequencies, the value may be within 10% on either side of the midpoint.

15, an exemplary computer system 1300 having one or more computing units capable of implementing the various systems and methods discussed herein is detailed. The computer system 1500 may be part of a controller, may be in operative communication with the various embodiments discussed herein, may perform various operations associated with the methods discussed herein, may process various data offline to characterize a battery, or may be part of an overall system discussed herein. The computer system 1500 may process and/or provide various signals discussed herein. For example, such a computer system 1500 may be provided with battery measurement information. The computer system 1500 may also be applicable to, for example, the controllers, models, and regulation/shaping circuits discussed with respect to the various figures, and may be used to implement the various methods described herein. Of course, the specific implementation of these devices may be of various possible specific computer architectures, not all of which are specifically discussed herein, but which will be understood by those skilled in the art. It will further be appreciated that the computer system may be considered and/or include an ASIC, FPGA, microcontroller, or other computer configuration. Various such possible implementations may include fewer or more of the components described below, and may have interconnections and other modifications, as will be appreciated by those skilled in the art.

The computer system 1500 may be a computer system capable of executing a computer program product to execute a computer process. The computer system 1500 receives data and program files, reads the files, and executes the programs therein. Some of the elements of the computer system 1500 are shown in FIG. 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. The computer system 1500 may also include other elements that one skilled in the art will recognize, but which are not explicitly shown in FIG. 15 or otherwise discussed herein. The various elements of the computer system 1500 may communicate with each other by one or more communication buses, point-to-point communication paths, or other communication means not explicitly shown in FIG. 15. Similarly, in various embodiments, the various elements disclosed in this 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 cache levels. The presence of one or more processors 1502 may result in processor 1502 having a single central processing unit or multiple processing units capable of executing instructions and performing operations in parallel with one another (commonly referred to as a parallel processing environment).

In various possible combinations, the techniques described herein may be implemented at least in part in software stored in data storage device 1504, in software stored in memory device 1506, and/or in software communicated via one or more of ports 1508-1512, such that computer system 1500 of FIG. 15 is a dedicated machine for performing the operations described herein.

The one or more data storage devices 1504 may include non-volatile data storage devices capable of storing data generated or employed within the computer 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 computer system 1500. Data storage devices 1504 include, but are not limited to, magnetic disk drives, optical disk drives, solid state drives (SSDs), flash drives, and the like. Data storage devices 1504 may include removable data storage media, non-removable data storage media, and/or external storage devices available via a wired or wireless network architecture with one or more computer program products, such as database management products, web server products, application server products, and/or other additional software components. Examples of removable data storage media include compact disc read-only memories (CD-ROMs), digital versatile disc read-only memories (DVD-ROMs), 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 (e.g., dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and/or non-volatile memory (e.g., read-only memory (ROM), flash memory, etc.).

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

In some embodiments, computer system 1500 includes one or more ports, such as input/output (I/O) port 1508, communication port 1510, and subsystem port 1512, for communicating with other computer, network, or vehicle equipment. Of course, ports 1508-1512 may be combined or separated, and computer system 1500 may include more or fewer ports. I/O port 1508 may be connected to devices, such as I/O devices, that input or output information to computer 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, motion, physical touch or pressure, and/or the like, into electrical signals as input data to the computer system 1500 via the I/O port 1508. In some examples, such inputs may be different than the various systems and methods discussed with respect to the preceding figures. Similarly, the output device may convert electrical signals received from the computer system 1500 via the I/O port 1508 into signals that can be detected or used by the various methods and systems discussed herein. The input device may be an alphanumeric input device including keys, such as alphanumeric characters, for communicating 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 for input to or output from the computer system 1500 via the I/O port 1508. For example, an electrical signal generated within the computer system 1500 may be converted into another type of signal, and/or vice versa. In one embodiment, the environmental transducer device senses characteristics or aspects of the environment proximate to or remote from the computer equipment 1500, such as battery voltage, open circuit battery voltage, charging current, battery temperature, light, sound, temperature, pressure, magnetic field, electric field, chemical properties, and/or similar properties.

In one embodiment, the communication port 1510 may be connected to a network from which the computer system 1500 may receive network data useful in performing the methods and systems described herein, as well as transmitting information and network configuration changes it determines. For example, charging protocol updates, sharing battery measurement or computational data with external systems, etc. The communication port 1510 connects the computer system 1500 to one or more communication interface devices configured to transmit and/or receive information between the computer system 1500 and other devices over 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, Bluetooth, Near Field Communication (NFC), Long Term Evolution (LTE), etc. One or more such communication interface devices may be utilized to communicate with one or more other machines via communication port 1510 directly over a point-to-point communication path, via a wide area network (WAN) (e.g., the Internet), via a local area network (LAN), via a cellular (e.g., third generation (3G), fourth generation (4G), fifth generation (5G)) network, or via another communication means.

Computer system 1500 may include a subsystem port 1512 for communicating with one or more systems associated with a device to be charged in accordance with the methods and systems described herein to control the operation of the device and/or exchange information between computer system 1500 and one or more subsystems of the device. Examples of such subsystems for a vehicle include, but are not limited to, motor controllers and systems, battery control systems, etc.

The system depicted in FIG. 15 is merely one possible example of a computer system that may employ or be configured in accordance with aspects of the present disclosure. Of course, other non-transitory, tangible, computer-readable storage media may be utilized that store computer-executable instructions for implementing the techniques disclosed herein on a computer system.

Embodiments of the present disclosure include various operations described herein. These operations may be performed by hardware components or embodied in machine-executable instructions that may be used to perform the operations by a general-purpose or special-purpose processor programmed with these instructions. Alternatively, these operations may be performed by a combination of hardware, software, and/or firmware.

Various modifications and additions can be made to the exemplary embodiments described without departing from the scope of the present disclosure. For example, while the above-described embodiments (also referred to as implementations or examples) depict certain features, the scope of the present invention also includes embodiments including different combinations of features and embodiments that do not include all of the above features. Accordingly, the scope of the present invention is intended to include all such alternatives, modifications, and variations, together with their respective equivalents.

Although specific implementations, examples, and embodiments (terms used interchangeably herein) have been discussed, it is to be understood that they are for illustrative purposes only. Those skilled in the art will recognize that other components and configurations can be used without departing from the spirit and scope of the present disclosure. For this reason, the above description and drawings are to be taken as illustrative and not limiting in any way. Numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, in certain instances, well-known or conventional details are not set forth in order to avoid obscuring the description.

Reference to "one embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase "in one embodiment," as well as the phrase "in one example" or "in one instance," or similar phrases in various places throughout this specification, do not necessarily all refer to the same embodiment or to separate or alternative embodiments that are mutually exclusive of other embodiments. Furthermore, various features are described that may be exhibited in some embodiments but not in other embodiments.

The terms used herein generally have their ordinary meaning in the art, in the context of this disclosure and in the particular context in which each term is used. In addition, alternative expressions and synonyms may be used for any one or more of the terms discussed herein, and no special emphasis should be placed on the recitation or explanation of a term in this specification. In some cases, synonyms of a particular term are provided. The recitation of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification, including examples of any term discussed herein, is for illustrative purposes only and is not intended to further limit the scope and meaning of the disclosure or any exemplary term. Similarly, the disclosure is not limited to the various embodiments described herein.

Without intending to limit the scope of the disclosure, examples of instruments, devices, methods, and their associated results according to embodiments of the disclosure are provided above. For the convenience of the reader, the examples may be given titles or subtitles, but this is not intended to limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meanings that are commonly understood by those of ordinary skill in the art to which the disclosure pertains. In the event of any conflict, the present specification, including definitions, will control.

Various features and advantages of the present disclosure have been set forth in the foregoing description, and some will be apparent from the description or may be learned by practice of 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:
1. A method comprising: generating and applying to a battery a repetitive signal defining a sinusoidal leading edge over a period of time that rises into a body portion terminating in a trailing edge, the repetitive signal including a first portion defining a first percentage of the period, and a second portion including an alternating current following the trailing edge of the first portion and defining a second percentage of the period, the first percentage and the second percentage constituting the period. The method of claim 1, wherein the repetitive signal is a current signal. The method of claim 1, wherein the sinusoidal leading edge is a first frequency associated with a first harmonic that has a relatively low impedance when applied to the battery compared to other harmonics. The method of claim 1, wherein the alternating current is centered around zero amperes. The method of claim 1, wherein the alternating current defines a sine wave having a positive current portion and a negative current portion. The method of claim 1, wherein the AC current is applied with a positive DC offset. The method of claim 3, wherein the sinusoidal leading edge is changed to a second frequency of the second harmonic if the impedance of the second harmonic is lower than the impedance of the first harmonic. The method of claim 1, wherein the second portion goes from alternating current to zero charging current when the temperature of the battery rises to about a threshold. The method of claim 8, wherein the temperature of the battery is based on a sensed temperature. The method of claim 8, wherein the temperature of the battery is based on a time of application of the repetitive signal, and the second portion includes the alternating current. The method of claim 1, wherein the repeating pattern is applied to the battery when the battery temperature is below a threshold. The method of claim 1, further comprising generating and applying an alternating current signal to the battery below a certain temperature, and then generating the repeating signal including the first portion and the second portion when the battery reaches the temperature. 1. A method for charging a battery, comprising:
applying a probe signal including a plurality of harmonics including at least a first harmonic and a second harmonic to the battery;
obtaining a voltage response and a current response at the battery based on the probe signal;
generating an impedance spectrum based on the voltage response and the current response, the impedance spectrum including at least a first impedance of the first harmonic and a second impedance of the second harmonic, the first impedance being lower than the second impedance;
generating and applying to the battery a charging signal including a sinusoidal leading edge at a frequency of the first harmonic;
Including, charging method. The charging method of claim 13, wherein the charging signal is a repeating signal in which the sinusoidal leading edge is followed by a body portion, and the body portion is followed by a heating portion that includes an alternating current waveform. The charging method of claim 14, wherein the alternating current waveform is centered around zero amperes. The charging method of claim 13, wherein the probe signal is a square wave centered at zero amperes. The charging method of claim 16, wherein the square wave has a 50% duty cycle over a period of approximately 30 milliseconds. A method of charging a battery that takes temperature into account, comprising:
Identifying a first charging current based on a current battery temperature, the first charging current being a current that will not overheat the battery at a time after maximum current sustained charging, and identifying a second charging current being a current that may be used at the current temperature of the battery;
initiating a charging signal for the battery at the lower of the first charging current or the second charging current;
Including, charging method. The charging method of claim 18, wherein identifying the first charging current is further based on an ambient temperature. The charging method according to claim 18, wherein the first charging current and the second charging current are limited by the supply capacity of either of the currents. The charging method of 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 including a first portion followed by a second portion, and the first portion including a sinusoidal leading edge followed by a main portion. The charging method of claim 21, wherein the second portion is a rest portion at zero amperes. The charging method of claim 22, wherein the average current is used to define the leading edge of the sinusoid and the peak current of the main body portion. 22. The charging method of claim 21, wherein the second portion is a non-zero DC charging current, and the average current defines the sinusoidal leading edge and peak current of the body portion and the non-zero DC charging current. 1. A method for heating a battery, comprising:
A method comprising applying an alternating current to a battery at a frequency higher than an inflection point in a conductance response or lower than an inflection point in a susceptance response to heat the battery. The method of claim 25, wherein the frequency is higher than the frequency at an inflection point in the conductance response and lower than the frequency at an inflection point in the susceptance response. A method for heating a battery, comprising applying an alternating current to the battery at a frequency that decreases the conductance response of the battery and increases the susceptance response of the battery to heat the battery. The method for heating a battery of claim 27, wherein the frequency is higher than the frequency at which the conductance response begins to degrade and lower than the frequency at which the susceptance response begins to degrade. The method for heating a battery according to claim 28, wherein the frequency at which the conductance response begins to decrease is at an inflection point where the conductance response is at a maximum. The method for heating a battery according to claim 28, wherein the frequency at which the susceptance response begins to decrease is at an inflection point at which the susceptance response is at a maximum. 28. The method of heating a battery of claim 27, wherein the frequency is in a range between a first frequency near where the conductance response of the battery begins to increase and then decrease, and a second frequency near where the susceptance response of the battery begins to increase and then decrease. The method of heating a battery of claim 31, wherein the first frequency is at an inflection point of the conductance response where the conductance response transitions from increasing to decreasing. The method of heating a battery of claim 31, wherein the second frequency is at an inflection point of the susceptance response where the susceptance response transitions from increasing to decreasing.

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