CN114583292A - Device for monitoring battery cells of a battery string in a sleep state - Google Patents

Device for monitoring battery cells of a battery string in a sleep state Download PDF

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Publication number
CN114583292A
CN114583292A CN202111458683.1A CN202111458683A CN114583292A CN 114583292 A CN114583292 A CN 114583292A CN 202111458683 A CN202111458683 A CN 202111458683A CN 114583292 A CN114583292 A CN 114583292A
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CN
China
Prior art keywords
battery
btx
band
voltage
battery cell
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Pending
Application number
CN202111458683.1A
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Chinese (zh)
Inventor
C·维克
S·博里
S·格洛格
M·霍伊泽
J·班德纳
P·谢尔
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Volkswagen AG
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Volkswagen AG
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Application filed by Volkswagen AG filed Critical Volkswagen AG
Publication of CN114583292A publication Critical patent/CN114583292A/en
Pending legal-status Critical Current

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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/396Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/482Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for several batteries or cells simultaneously or sequentially
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/42Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing

Abstract

The invention relates to a device (1) for monitoring battery cells (BT 1-BTX) of a battery string (10) in a sleep state, the device comprises a differential voltage unit (30) for each battery cell (BT 1-BTX), wherein a band-pass filter (35) is arranged downstream of each differential voltage unit (30), wherein the outputs of each two band-pass filters (35) are connected to the inputs of a differential amplifier (36) having a downstream rectifier (37), wherein the output of the rectifier (37) is connected to an input of a comparator (38), wherein the output of the comparator (38) is connected to at least one logic unit (40) for generating a monitoring signal, wherein the device (1) has an excitation circuit (20) which is designed to generate a discharge current within a predetermined time.

Description

Device for monitoring battery cells of a battery string in a sleep state
Technical Field
The present invention relates to an apparatus for monitoring battery cells of a battery string in a resting state.
Background
In the case of a battery cell in a battery string that has not yet been found to be damaged, for example, due to manufacturing defects, inadmissible heating or other damage, thermal runaway (thermal runaway) may occur. For security reasons, efforts are made to detect this event as early as possible. The known sensor device has various disadvantages.
For example, gas or pressure sensing devices are known, by means of which it is detected whether the battery cell is degassed. This is a relatively short time point before possible heat propagation, so that the reaction time is correspondingly shortened. Conventional cell voltage measurements are also slow relative to each other. Directly measuring the temperature on all battery cells is very complicated in terms of circuit technology. Another possible method is an impedance spectrum which performs current and voltage measurements and from which an impedance with amplitude and phase is determined as a function of frequency. Such a measurement cycle lasts several minutes and consumes a lot of energy.
Disclosure of Invention
The technical problem on which the present invention is based is therefore that of: an alternative device for monitoring battery cells of a battery string in a sleep state is provided, which enables an early warning of heat propagation.
A solution to this technical problem is obtained by the device according to the invention. Further advantageous embodiments of the invention emerge from the dependent claims.
The device for monitoring the battery cells of a battery string in a sleep state has a differential voltage unit for each battery cell of the battery string. Here, the battery string is a series connection of battery cells. Here, the battery string may be a battery module or an entire battery, for example a high-voltage battery of an electric vehicle or a hybrid vehicle. Here, by means of these differential voltage units, differential voltage measurements are made at both cell poles of the battery cell. Downstream of these differential voltage units, a band-pass filter is respectively arranged in order to limit the frequency range to a frequency band of particular effectiveness. The frequency band depends on the battery cell type, wherein in this case the results of the impedance spectrum measurements of these battery cell types can be used. The outputs of every two band-pass filters are connected to the inputs of a differential amplifier in order to detect in this way a deviation between the two output signals at the band-pass filters. In this case, respectively adjacent bandpass filters can be routed to a differential amplifier, but bandpass filters which are further away from one another can also be routed to a differential amplifier. The output of the differential amplifier is connected to a rectifier, preferably a bidirectional rectifier. Then, a unipolar voltage signal is present at the output of the rectifier. The output of the rectifier is then connected to the inputs of comparators, whose outputs are connected to the inputs of a logic unit for generating the monitoring signal, wherein the logic unit is an or gate in the simplest case. The device also has a drive circuit which is designed to generate a discharge current for a predetermined time. In this way, the battery string is subjected to a temporary load, which can be detected in the voltage change across the battery cells. These differential voltage changes are now compared to each other in a specific frequency band. In case the output signal at the bandpass filter deviates from the remaining output signal, this indicates that: there is damage to the battery cell and/or overheating compared to the other battery cells, which can therefore be detected without direct temperature measurement. If this is the case, the logic unit generates a signal in order to introduce the corresponding measures. For example, more complex monitoring devices can be activated, which have a higher quiescent current requirement, but for which an accurate check of the battery cells is possible. Alternatively or additionally, an alarm message may be generated and/or cooling of the battery cells may be initiated. The equipment has the advantages that: the device provides an initial indication of a possible failure of the battery cell without the need for a more complex microprocessor, where the quiescent current requirements are very low since many cells can be formed with passive components. Provision can be made here for: the active component, such as a differential amplifier, is connected to the supply voltage only during the measurement time, i.e. the driver circuit switches the device on and off.
In one embodiment, the excitation circuit has a relay or a semiconductor switch (e.g., MOSFET or IGBT) and a control circuit. The advantage of relays is galvanic isolation, but the achievable switching times are short compared to semiconductor switches, so that semiconductor switches should be preferred to perform faster measurements.
In a further embodiment, the control circuit is designed as a timer, and the control circuit then activates the excitation circuit or the device after a predetermined time and deactivates the excitation circuit or the device again after a predetermined time, respectively.
In a further embodiment, the drive circuit has a separate load resistor, or the semiconductor switch together with its volume resistance (durchgapswinderstand) forms the load.
In another embodiment, a differential voltage unit includes: two DC voltage filters respectively assigned to the battery poles; and a differential amplifier. The direct-current filter can also be referred to as a DC Blocker (DC-Blocker) and is designed in the simplest case as a capacitor. By the separation of the dc voltage component, the subsequent signal processing is significantly simplified, since then all signals can be measured against the same reference ground.
In a further embodiment, an amplifier is arranged between the dc voltage filter and the input of the differential amplifier. The amplifier is used here primarily for amplifying the voltage signal, but additionally filters out high-frequency components due to its inertia, which is advantageous for the subsequent differential amplifier and bandpass filter.
In another embodiment, the predetermined time is greater than 100 ms and less than 1 s, and preferably between 150 ms and 250 ms. In this way, a sufficiently long voltage response is generated, wherein the quiescent current requirements are very low.
In another embodiment, the lower limit frequency of the band-pass filter is greater than 50 Hz and the upper limit frequency is less than 500 Hz, further preferably the band-pass is a lower limit frequency of 100 Hz and an upper limit frequency of 300 Hz.
In a further embodiment, at least one battery cell is assigned a temperature sensor, wherein the device is designed to estimate the temperature of the battery cell based on the measurement result of the differential voltage unit and the measurement value of the temperature sensor without the temperature sensor.
In another embodiment, the device is part of a traction network of an electric or hybrid vehicle.
Drawings
The invention is described in more detail hereinafter according to a preferred embodiment. The sole figure shows a schematic block circuit diagram of an apparatus for monitoring battery cells of a battery string in a sleeping state.
Detailed Description
A block circuit diagram of a device 1 for monitoring a battery string 10 with a plurality of battery cells BT 1-BTX is shown in fig. 1. Here, a circuit-technical implementation of the device 1 for the first four battery cells BT 1-BT 4 is shown, wherein the continuation for the other battery cells BTX is only indicated by dashed lines. The device 1 has a drive circuit 20 having: as a timer 22, a load resistor 23 and a switching element 24 of the control unit 21, the switching element is preferably designed as a semiconductor switch 25. The device 1 also has a differential voltage unit 30 corresponding to the number of battery cells BT 1-BTX. Each differential voltage unit 30 has two dc voltage filters 31, which are each connected to the battery poles of the associated battery cells BT 1-BTX. The output terminals of the dc voltage filter 31 are connected to the input terminals of an amplifier 32, wherein two output terminals of the amplifier 32 are connected to the input terminals of a differential amplifier 34. The device 1 further has a band-pass filter 35, wherein the output terminals of the differential amplifier 34 are connected to the input terminals of the band-pass filter 35, respectively, which has, for example, a lower limit frequency of 100 Hz and an upper limit frequency of 300 Hz. The outputs of each two band pass filters are connected to the inputs of a further differential amplifier 36. Shown here are: the bandpass filters 35 of the first battery BT1 and the third battery BT3 are directed to a common differential amplifier 36; and the bandpass filters 35 of the second battery BT2 and the fourth battery BT4 are directed to a common differential amplifier 36. Other allocations are possible, such as: the respective directly adjacent band-pass filters 35 are combined in pairs. The outputs of the differential amplifier 36 are connected to the inputs of rectifiers 37, the outputs of which are connected to respective inputs of a comparator 38. A reference voltage source Vref is connected at the respective other input of the comparator 38. The output of the comparator 38 is connected to a logic unit 40, wherein the logic unit 40 is for example an or gate. The output of the logic unit 40 provides a monitoring signal which may be a trigger or wake-up signal of a more complex measuring device 50 for the battery cells BT 1-BTX. Finally, the device 1 also has at least one temperature sensor T assigned to the first battery cell BT 1.
The working principle of the device 1 shall now be briefly elucidated. The battery string 10 is in a sleep state such that no charge or discharge current flows. The control unit 21 of the excitation circuit 20 then activates the remaining part of the device 1 at a predefined time (for example every 15 minutes) and switches the switching element 24 closed for a predefined time, for example 200 ms, so that a load current can flow through the load resistor 23, wherein the switching element 24 is then opened again. This load current causes a voltage change at the battery cells BT 1-BTX. Ideally, these differential voltage variations at the battery poles are all of the same magnitude, i.e., all battery cells are subjected to the same large load. The dc voltage component is now blocked by a dc voltage filter 31 and only the alternating voltage component is allowed to pass for further processing, wherein the very high frequency components are filtered out by an amplifier 32 or a differential amplifier 34. Then, at the output of the differential amplifier 34, there is an alternating voltage of the individual battery cells BT 1-BTX as a voltage response to the brief load current of the excitation circuit 20. The frequency band of the voltage response is then limited to a range of significant forces by a band pass filter 35. Ideally, these signals at the output of the bandpass filter 35 are the same for all of the battery cells BT 1-BTX. Now, it is ascertained whether the two battery cells BT 1-BTX differ or not, by means of the following differential amplifier 36, which compares the signals of the two band-pass filters 35, respectively. If the voltage response of one battery cell BT 1-BTX differs from the voltage response of the other battery cells BT 1-BTX, this indicates that the different battery cell BT 1-BTX has manufacturing defects, is mechanically damaged, and/or is overheated. Since it is not now clear which of these battery cells BT 1-BTX is faulty, the output signal at the differential amplifier can be either positive or negative. This problem is solved by subsequent rectification by the rectifier 37. It is clear that the rectifier 37 converts a negative voltage into a positive voltage. These voltage signals of the rectifier 37 are now compared with a reference voltage source Vref at a comparator 38. If there is now a fault in the battery cells BT 1-BTX, the voltage present at the assigned rectifier 37 is greater than the reference voltage and a voltage signal is generated at the output of the comparator 38. This in turn generates a voltage signal at the output of the logic cell 40. The logic can also be modified in such a way that, for example, a voltage signal is always present at the output at the comparator 38 and the voltage only goes to zero if the voltage at the rectifier 37 is high. In this case, the logic unit 40 is an and gate.
List of reference numerals
1) Device
10) Battery pack string
20) Excitation circuit
21) Control unit
22) Timer
23) Load resistance
24) Switching element
25) Semiconductor switch
30) Differential voltage unit
31) DC voltage filter
32) Amplifier
34) Differential amplifier
35) Band-pass filter
36) Differential amplifier
37) Rectifier
38) Comparator with a comparator circuit
40) Logic unit
50) Measuring device
T) temperature sensor
BT 1-BTX) battery cell
Vref) reference voltage source

Claims (10)

1. A device (1) for monitoring battery cells (BT 1-BTX) of a battery string (10) in a sleeping state, the device comprises a differential voltage unit (30) for each battery cell (BT 1-BTX), wherein a band-pass filter (35) is arranged downstream of each differential voltage unit (30), wherein the outputs of each two band-pass filters (35) are connected to the inputs of a differential amplifier (36) having a downstream rectifier (37), wherein the output of the rectifier (37) is connected to an input of a comparator (38), wherein the output of the comparator (38) is connected to at least one logic unit (40) for generating a monitoring signal, wherein the device (1) has an excitation circuit (20) which is designed to generate a discharge current within a predetermined time.
2. Device according to claim 1, characterized in that the excitation circuit (20) has a relay or a semiconductor switch (25) and a control unit (21).
3. The device according to claim 2, characterized in that the control unit (21) is designed as a timer (22).
4. A device according to any one of claims 2 or 3, characterized in that the excitation circuit (20) has a separate load resistance (23) or the semiconductor switch (25) constitutes a load.
5. Device according to any one of the preceding claims, characterized in that the differential voltage unit (30) has: two DC voltage filters (31) which are each associated with a battery pole of a battery cell (BT 1-BTX); and a differential amplifier (34).
6. The device according to claim 5, characterized in that an amplifier (32) is arranged between the direct current filter (31) and the input of the differential amplifier (34), respectively.
7. Device according to any one of the preceding claims, characterised in that said predetermined time is greater than 100 ms and less than 1 s.
8. Device according to any one of the preceding claims, characterized in that the lower frequency of the band-pass filter (35) is greater than 50 Hz and the upper frequency is less than 500 Hz.
9. An apparatus according to any one of the preceding claims, characterized in that at least one battery cell (BT 1-BTX) is assigned a temperature sensor (T), wherein the apparatus (1) is designed to estimate the temperature of the battery cell (BT 1-BTX) based on the measurement of the differential voltage unit (30) without the temperature sensor (T).
10. An arrangement according to any one of the foregoing claims, characterised in that the arrangement (1) is part of the traction network of an electric or hybrid vehicle.
CN202111458683.1A 2020-12-02 2021-12-02 Device for monitoring battery cells of a battery string in a sleep state Pending CN114583292A (en)

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Application Number Priority Date Filing Date Title
DE102020215243.8A DE102020215243B4 (en) 2020-12-02 2020-12-02 Device for monitoring battery cells in a battery string in the idle state
DE102020215243.8 2020-12-02

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DE102022121923A1 (en) 2022-08-30 2024-02-29 Cariad Se DETECTING AN ELECTRICAL CELL VOLTAGE OF A SINGLE BATTERY CELL IN A SERIES CONNECTION OF BATTERY CELLS

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DE102020215243B4 (en) 2023-05-11

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