DE102021133462B4 - battery and battery control methods - Google Patents

Abstract

Method for operating a battery, in particular a battery which is connected to a consumer and a central control and monitoring unit of the consumer, wherein the battery has a battery management system (BMS) and at least one cell pack, wherein an individual measurement of the temperature of the battery and/or at least one cell pack is carried out in regular measurement periods, wherein
the individual measurement of the temperature is carried out in idle mode of the battery, whereby an alarm function is carried out for regular checking after a defined idle period, thereby
characterized by
the individual temperature measurements are stored in a non-volatile data memory, and a continuous temperature exposure in idle mode (TE _R ) of the battery is determined from the individual measurements and stored in the non-volatile data memory.

Description

The present invention relates to a method for operating a battery according to the preamble of claim 1 and a battery according to the preamble of claim 11.

Batteries, especially HV batteries, which have a large number of cell packs, are monitored for electrical and physical conditions, including monitoring the temperature, which is done regularly when the battery is in operation. This also includes monitoring thermal conditions, particularly the detection of so-called thermal breakdowns. The disadvantage of known solutions is that the battery is only monitored when it is in operation.

While the system is in sleep mode, no status monitoring is possible. The system is only woken up via TLF wakeup or CAN wakeup and wakes up the entire system. These two technologies are used to enable coordinated waking up of a defined/selectable/arbitrary number of cell packs.

The battery control unit used for this requires a power supply via the low-voltage network (LV) of the consumer, usually the vehicle. To minimize consumption, the control unit is switched off when the vehicle and the battery are idle, for example when parking. This means that the status data is not monitored while parking.

From the DE 101 31 259 A1 A method for determining a battery temperature is known.

From the DE 10 2011 089 962 A1 A method for controlling the temperature of at least one battery element, a battery and a motor vehicle with such a battery are known.

It is the object of the present invention to provide an improved method for detecting and predicting the condition of the battery.

This object is achieved according to the invention by a method according to the features of claim 1 and a battery according to the features of claim 10. Advantageous embodiments are specified in the respective associated subclaims.

The object is then achieved by a method for operating a battery, in particular a battery which is connected to a consumer and a central control and monitoring unit of the consumer, wherein the battery has a battery management system (BMS) and at least one cell pack. The consumer can in particular be a motor vehicle, although this should not be restricted to this, and can also be a rail vehicle, watercraft or an aircraft. The invention can also be used for stationary battery storage systems.

According to the invention, an individual measurement of the temperature of the battery and/or at least one cell pack is carried out in regular measurement periods, the individual measurement of the temperature being carried out when the battery is in idle mode, for which purpose an alarm function is carried out during idle mode for regular checking after a defined idle period. The individual temperature measurements are subsequently stored in a non-volatile data memory, and a continuous temperature exposure in idle mode (TE _R ) of the battery is determined from the individual measurements and stored in the non-volatile data memory.

In this case, the term “cell pack” should be understood as a synonym for an internal component of the battery, such as battery cell, battery compartment, etc.

A more comprehensive embodiment of the method consists in measuring the temperature and/or the temperature profile of the battery and/or at least one cell pack during operation of the battery and also storing this in the non-volatile data memory as a temperature exposure in operating mode. This temperature exposure in idle mode and the temperature exposure in operating mode are ideally combined and merged to form an overall temperature exposure of the battery and/or the at least one cell pack.

The data storage device can be arranged at any location within or on the battery and in particular within the battery management system and is connected to the respective components in a suitable and not further described manner in such a way that it conducts data and, if necessary, also conducts current.

Since recording the temperature over the entire time would require a very large amount of storage space, an improvement in the method is to store the temperature exposures as discrete values of a total time period per temperature range and/or to store and update this temperature range of, for example, ΔT = 5 °C to 10 °C. This storage of the temperature as a frequency distribution represents a mas This represents a significant reduction in the amount of data that needs to be stored, compared to storing every single temperature point at every point in time over the lifetime. By storing the temperature as a frequency distribution, it is possible to determine how long the battery has remained within a temperature range. In this way, appropriate follow-up steps for warning, control and/or regulation can be derived based on summary exposure times in very high or very low temperature ranges.

In order to keep the number of individual measurements as low as possible, particularly in idle mode, and thus to limit battery discharge to a minimum, one improvement is to estimate the temperatures and thus the total exposure times of the battery and/or the at least one cell pack, for example in a temperature interval, between two individual measurements on the basis of a calculation formula. When making this estimate, it can advantageously be assumed that there is a constant increase or decrease in temperature between two individual measurements for the calculation formula. This estimate should be made in particular if the measurement period between two individual measurements is less than or equal to 2 hours and/or does not cover turning points in relation to the local time of day, such as the morning hours, midday or times of sunset. A further improvement is therefore that the geographical location of the battery, the time of year there and/or the history data of the position of the sun are used to determine the measurement period. Ideally, the measurement periods are less than or equal to one hour.

When defining the measurement period, it is necessary to consider how many memory cycles are possible in the data memory and how high the maximum energy consumption of the microprocessor can be. Ideally, the measurement periods are as short as possible.

A key advantage of this invention is that instead of an active measurement with high energy consumption, a very energy-saving estimation of the battery temperature is carried out over the entire lifetime (operation and non-operation).

• T ist konstant
• T(t) hat einen linearen (geraden)Verlauf
• T(t) hat den Verlauf gemäß einer Gleichung zweiter oder höherer Ordnung, insbesondere einer Hyperbel

Advantageously, the temperature curve between individual measurements at time t ₁ and t ₂ is estimated according to at least one of the following calculation formulas T(t):

• T is constant
• T(t) has a linear (straight) course
• T(t) has the course according to a second or higher order equation, in particular a hyperbola

For T(t), the step response in first order is as follows: $$\mathrm{\Delta }\text{T}\left(\text{t}\right)=\text{k}\left(1-\text{e}\left(-\text{t/}\mathrm{\tau }\right)\right)$$

The exposure time of the battery or battery cell can be estimated as follows: $$\mathrm{\Delta }{\text{t = t}}_2-{\text{t}}_1=\left|\mathrm{\tau }\text{ln}\left[\left({\text{T}}_1-{\text{T}}_{\text{au}ß\text{en}}\right)/\left({\text{T}}_2-{\text{T}}_{\text{au}ß\text{en}}\right)\right]\right|.$$

• k: Offset zwischen Umgebungstemperatur direkt außerhalb der Zelle oder des Zellenpacks und der Temperatur der Zelle oder des Zellenpacks, unabhängig von der Isolation.
• T: Temperatur der Batterie in K
• T_außen: Temperatur in K der Atmosphäre
• τ: charakteristische Abkühlzeit ohne Isolation in Sekunden, die laborseitig mittels Thermotests ermittelt wurde.

Herein means

• k: Offset between ambient temperature directly outside the cell or cell pack and the temperature of the cell or cell pack, independent of insulation.
• T: Battery temperature in K
• T _outside : temperature in K of the atmosphere
• τ: characteristic cooling time without insulation in seconds, determined in the laboratory by means of thermal tests.

A particular advantage and a component of the invention is that no direct measurement of the ambient temperature is necessary, which would have to be carried out via the central control unit of the vehicle and would have a correspondingly high energy requirement.

• - der Temperatur der Batterie und/oder der mindestens einen Zellpackung oder zusätzlich
• - der Außentemperatur (T_außen) veranlasst.

The method can be further improved in that the battery management system (BMS) and/or the central control and monitoring unit of the consumer comprises at least one microcontroller, which, after a defined rest phase, carries out the individual measurements

• - the temperature of the battery and/or the at least one cell pack or additionally
• - the outside temperature (T _outside ).

• - Warn- und Hinweissignale gesendet werden und/oder
• - Steuer- und/oder Regelungsdaten an die Batterie und/oder einen angeschlossenen Verbraucher gesendet werden, insbesondere Daten über eine prognostizierte Leistungsabgabe/-dauer.

From the individual measurements recorded and stored in this way, the derived data or the measured values, the battery management system (BMS) can advantageously determine the temperature exposure in idle mode (TE _R ) and/or in operating mode (TE _B )

• - warning and information signals are sent and/or
• - Control and/or regulation data are sent to the battery and/or a connected consumer, in particular data on a forecast power output/duration.

In this context, warning and information signals are all optically and/or acoustically perceptible indications, in particular those that provide information on the status or performance data of the battery and information derived from this, such as changes in the range for a consumer's journey due to the performance, including the ageing effects from long exposure times in certain temperature ranges.

In this case, “standby mode” of the battery means that the consumer is switched off and the battery is not used as a voltage source for this. In particular, in standby mode the battery is not used by a consumer to power it (working mode), not even in short-term generator mode. Furthermore, “standby mode” does not mean “charging mode”, in which the battery is charged at a stationary charging station. Furthermore, “checking” or “checking step” means all measurements, recordings and data evaluations that can also be related to and for the purpose of detecting a thermal event (thermal runaways).

An advantageous variant of the method is that the rest period until the next individual measurement depends on the respective level of the last individual measurement, so that, for example, at very high or very low temperatures, a short period of time, for example less than 30 minutes, is selected until the next individual measurement in order to estimate the ageing of the battery as accurately as possible. At moderate temperatures, however, a longer period of time of up to 2 or 3 hours can be selected between the individual measurements because this has only a smaller influence on the ageing of the battery.

The particular advantage is that this method allows for a virtually complete monitoring of the condition of the battery system with regard to temperature exposure, so that its aging and in particular its performance and service life can be optimally estimated.

One improvement is that the wake-up function is outsourced from the main control unit to at least one microcontroller that is not located on the main control unit or the motherboard. This has the advantage that this simple wake-up function can be performed by any downstream microcontroller, so ideally the battery microcontroller should be chosen whose operation requires the least energy.

When waking up, all components are activated that are required to measure the battery temperature, calculate the above formulas and store the data in the non-volatile memory. If the waking up is done by a downstream microcontroller without waking up the main board, it must be ensured that all of the necessary components described are also present on this downstream microcontroller.

Overall, an improvement is that the time period from the last cyclical wake-up to an externally initiated wake-up or system start, which is smaller than the defined wake-up cycle, is recorded and stored in order to avoid a "blind spot" between the last cyclical wake-up of the battery and the externally initiated wake-up. For this purpose, at least one corresponding time-recording hardware component is provided on a cell measurement board or a microprocessor of a higher-level main control system.

The invention further includes a battery for a consumer, the consumer being in particular a vehicle (car). The battery is designed as a high-voltage battery (HV battery) and comprises a battery management system (BMS) and at least one temperature sensor for detecting the temperature of the battery and/or at least one cell pack of the battery. Advantageously, a plurality of temperature sensors are arranged, in particular one temperature sensor is arranged on each cell/pack. The temperature sensors are arranged on or at the battery cells whose own temperature or the temperature of a neighboring cell is to be monitored. The temperature sensor is connected to the control unit in a data-conducting manner.

The battery management system (BMS) is designed to carry out temperature detection and data storage according to one of the previous process variants.

In an improved embodiment of the battery, the battery management system (BMS) has at least one temperature sensor and/or is connected to at least one temperature sensor, by means of which the outside temperature can be detected directly or indirectly. In a further improvement of the battery according to the invention, a central control and monitoring unit of the consumer is connected to the battery and/or the battery management system (BMS), wherein the central control and monitoring unit is designed to carry out partial calculations of the temperature exposure, storage of the associated data and/or measured values or control the rest period.

In a further embodiment of the battery, it comprises at least one further temperature sensor on or on a main board, wherein the temperature sensor is connected in a data-conducting manner directly or indirectly to a microprocessor and/or a main control unit of the battery. Since this (central) temperature sensor is arranged spatially away from the battery cells or cell packs, a temperature measurement can be taken using this central temperature sensor, which is usually closer to the ambient temperature and can also serve as a control measurement for specific cell temperatures.

In this context, “being connected” or “being in connection” is not to be understood in a restrictive sense and means one or more connections to the voltage and power supply as well as to data-conducting communication. The communication can in particular be designed as one of the usual bus technologies or serial interfaces, through separate individual cables or modulated onto one or more current-carrying individual cables.

The great advantage of this solution is that a complete history of the temperature exposure of the battery is carried out in a very energy-saving manner when the consumer is switched off and the battery is in idle mode, and this data can be used to evaluate the service life, safety and performance of the battery.

Further details and advantages of the invention will now be explained in more detail with reference to an embodiment shown in the drawings.

• 1 den Temperaturverlauf der Batterie über eine Expositionsdauer im Betriebs- und im Ruhebetrieb,
• 2 den Temperaturverlauf der Batterie nach 1, wobei lineare Abschätzungen der Temperaturverläufe im Ruhebetrieb vorgenommen wurden und
• 3 den Temperaturverlauf der Batterie nach 1 mit einer zur 2 alternativen Abschätzung der Temperaturläufe im Ruhebetrieb.

They show:

• 1 the temperature profile of the battery over an exposure period in operating and idle mode,
• 2 the temperature curve of the battery after 1 , whereby linear estimates of the temperature profiles were made during idle operation and
• 3 the temperature curve of the battery after 1 with a 2 alternative estimation of the temperature runs during idle operation.

In the 1 is the temperature curve 1 of the HV battery (not shown) over an exposure period in operating mode I and in idle mode II. The temperature curve 1 shown as a solid line represents the theoretical, ideal graph of cooling, assuming complete knowledge. If the consumer (not shown) and/or the battery is switched off at switch-off time 2, the battery cools down steadily depending on the outside temperature T _outside marked with the reference number 7, which was assumed to be constant in this case. At the four wake-up or measurement times 3.1 ... 3.4 shown, after a time interval of 2 hours each, an individual measurement was taken and the current temperature of the battery or at least one cell pack was determined.

The last time interval (end phase 6) between the measurement time 3.4 and the renewed start of operating mode I at the start time 4, when the car is used again, for example, is shorter than the previous time intervals. For the sake of simplicity, it was assumed that the time of waking and the time of measurement are identical, which is of course not the case in reality, since there are different processes in the case of waking that cover a certain period of time, as well as the actual measurement process, which has little or no relevance for the time spans of several minutes to hours from an individual measurement to the subsequent individual measurement. As soon as the battery has been woken up, the temperature is recorded at very high sampling rates of 10 Hz, for example. The battery temperature is therefore always (approximately) at the time of waking up, so that a measurement is always taken at the time of starting the vehicle, for example.

To calculate the time of this “blind spot” between the last cyclical wake-up of the battery and the externally initiated wake-up of the battery, a corresponding hardware component is advantageously integrated on the cell measurement board or the microprocessor of a higher-level main control system.

In the simplest embodiment of a complete recording of the temperature-dependent exposure of the battery over time at a particular temperature level, the temperature of the respective last individual measurement can be assumed to be constant and continued until the subsequent individual measurement in a conservative, safety-oriented estimate. In the present example, this would result in five temperatures/levels, from the switch-off time to the first measurement time 3.1 in idle mode I, three temperatures/levels between the measurement times 3.1 ... 3.3 and the temperature or temperature level from the fourth measurement time 3.4 to the start time 4.

Alternatively, the exposure could be estimated and recorded using temperatures in such a way that the temperature determined at the respective measurement time 3.1 ... 3.4 is assumed to be constant in advance. This would be done analogously for the final phase, for which the temperature at the start time 4 would be assumed to be constant in advance.

Alternatively, the average of the temperatures at two waking times can be used.

In the example after 2 is the temperature curve 1 of the battery after 1 given, whereby a linearly decreasing estimate of the temperature profiles 5.1 ... 5.4 in idle mode II was made for the respective periods between the individual measurements 3.1 ... 3.4. As can be clearly seen, the temperature change in the final phase 6 before the start time 4 is only very slight and, with regard to the gradient, very similar to the previous period 5.4, so that the temperature profile according to 5.4 could be prescribed up to the start time.

In the embodiment according to 3 is to be understood analogously to the previous figures, whereby the temperature curve in the resting phase II between the individual measurements was estimated using a first-order Eulerian equation.

The following relationship was assumed for each time interval between two individual measurements 3.1 ... 3.4 in the resting phase II: $$T_{\text{B}}\left(t\right)=T_{\text{B}}\left(t_1\right)\left(e\left(-t/\tau \right)\right)+T_{\text{au}ß\text{en}}\left(1-e\left(-t/\tau \right)\right)$$

• ▪ t₁, t₂ die Zeitpunkte der Messung
• ▪ T_B die Temperatur der Batterie und/oder eines Zellpacks, wobei T_B(t₁) entspricht T₁ und T_B(t2) entspricht T₂.
• ▪ T_außen die Temperatur außerhalb der Batterie und/oder des Zellpacks, insb. Umgebungstemperatur
• ▪ τ die charakteristische Abkühlzeit als laborseitig bestimmter Verlauf der Abkühlung der Batterie ohne Isolierung.

Here is/are

• ▪ t ₁ , t ₂ the times of the measurement
• ▪ T _B is the temperature of the battery and/or a cell pack, where T _B (t ₁ ) corresponds to T ₁ and T _B (t2) corresponds to T ₂ .
• ▪ T _outside the temperature outside the battery and/or the cell pack, especially the ambient temperature
• ▪ τ is the characteristic cooling time as the laboratory-determined cooling course of the battery without insulation.

Furthermore, the outside temperature can be estimated from the measured battery temperatures and the characteristic cooling time, so that it is independent of the direct measurement of the ambient temperature. The ambient temperature can be estimated, for example, using the following equation: $$T_{\text{au}ßen}=\left(T_{\text{B}}\left(t\right)-T_{\text{B}}\left(t_1\right)\mathrm{\ast }\left(e\left(-t/\tau \right)\right)/\left(1-e(-t/\tau \right)\right)$$

Analogous to the previous process variants, the temperature curve in the final phase 6 can be estimated from the previous curve 5.4 by means of extrapolation.

It is understood that the parabolic temperature curve of the cooling of the battery can also be estimated and approximately described using other suitable mathematical methods.

In particular, a critical fault (thermal runaway) can be immediately concluded if the temperature of the battery continues to rise during idle mode, contrary to the lower temperature level of the environment.
Furthermore, a critical fault can be immediately concluded if the temperature of an individual cell or cell module continues to rise, contrary to the temperatures of the other cells or cell modules.

list of reference symbols

1

temperature curve

2

shutdown time

3

Wake-up and measurement time (also 3.1, ... 3.4)

4

start time

5

Temperature profile, estimated (also 5.1 ... 5.4)

6

final phase

I

operating mode

II

idle mode

Claims (12)

Method for operating a battery, in particular a battery which is connected to a consumer and a central control and monitoring unit of the consumer, wherein the battery has a battery management system (BMS) and at least one cell pack, wherein an individual measurement of the temperature of the battery and/or at least one cell pack is carried out in regular measurement periods, wherein the individual measurement of the temperature is carried out when the battery is in idle mode, wherein a wake-up function is carried out for the idle mode for regular checking after a defined idle period, characterized in that the individual measurements of the temperature are stored in a non-volatile data memory, and From the individual measurements, a continuous temperature exposure in idle mode (TE _R ) of the battery is determined and stored in the non-volatile data memory. procedure according to claim 1 , characterized in that the temperature and/or the temperature profile of the battery and/or at least one cell pack is measured during operation of the battery and is stored in the non-volatile data memory as temperature exposure in operating mode (TE _B ). procedure according to claim 1 or 2 , characterized in that the temperature exposure in idle mode (TE _R ) and the temperature exposure in operating mode (TE _B ) are combined to form a total temperature exposure (TE _G ) of the battery and/or the at least one cell pack. Method according to one of the preceding claims, characterized in that the temperature exposure (TE _G , TE _R , TE _B ) is stored and updated as discrete values of a total time period per temperature range. Method according to one of the preceding claims, characterized in that the temperatures of the battery and/or the at least one cell pack between two individual measurements are estimated on the basis of a calculation formula. procedure according to claim 5 , characterized in that the calculation formula assumes a continuous increase or decrease in temperature between two individual measurements. Method according to one of the Claims 5 or 6 , characterized in that the temperature curve between individual measurements is estimated using at least one of the following calculation formulas - a linear curve - a curve according to an equation of at least 2nd order, such as a hyperbolic section, in particular as a continuously falling hyperbolic section and/or as Δt = t ₂ - t ₁ = | τ In [(T ₁ - T _outside )/(T ₂ -T _outside )]|, where τ in seconds represents the characteristic cooling time without insulation. Method according to one of the preceding claims, characterized in that the battery management system (BMS) and/or the central control and monitoring unit of the consumer comprises at least one microcontroller which, after a defined rest phase, initiates the individual measurement of - the temperature of the battery and/or of the at least one cell pack and/or - the outside temperature (T _outside ). Method according to one of the preceding claims, characterized in that the battery management system (BMS) sends - warning and information signals and/or - control and/or regulation data to the battery and/or a connected _consumer , in particular data on a predicted power output/duration, depending on the temperature exposure in idle mode (TE _R ) and/or in operating mode (TE B ). Method according to one of the preceding claims, characterized in that the time period which is smaller than the specified measurement period of an individual measurement is recorded and stored during an externally initiated wake-up and/or system start, for which purpose at least one time-recording hardware and/or software component is provided on at least one cell measurement board and/or the central controller. Battery (1) for a consumer (3), in particular a vehicle, designed as a high-voltage battery (HV battery), comprising a battery management system (BMS) and at least one temperature sensor for detecting the temperature of the battery and/or at least one cell pack, characterized in that - the battery management system (BMS) is designed to carry out the method according to one of the Claims 1 until 10 to execute. battery after claim 11 , characterized in that the battery management system (BMS) has at least one temperature sensor and/or is connected to at least one temperature sensor by means of which the outside temperature (T _outside ) can be detected.