WO2016020149A1

WO2016020149A1 - Self-discharge characterizing device and method for characterizing a self-discharge of energy stores

Info

Publication number: WO2016020149A1
Application number: PCT/EP2015/066013
Authority: WO
Inventors: Stefan Butzmann; Marco Friedrich; Bernhard Springer
Original assignee: Robert Bosch Gmbh
Priority date: 2014-08-04
Filing date: 2015-07-14
Publication date: 2016-02-11
Also published as: DE102014215290A1

Abstract

Self-discharge characterizing device (1) for one or a plurality of interconnected battery cells (10 – 15), wherein the self-discharge characterizing device (1) comprises an electrical reference energy store (22), which provides a reference voltage and which can be charged with energy from the battery cell or battery cells (10 – 15), wherein after charging the reference voltage is at least approximately equal to a battery voltage of the one or the plurality of battery cells (10 – 15), and the self-discharge characterizing device is designed to use, at a point in time after the charging of the reference energy store (22), changes in the battery voltage and the reference voltage for the purpose of detecting a self-discharge of the battery cell(s) (10 – 15) and/or a state of the battery cell(s) (10 – 15), wherein the self-discharge characterizing device comprises a compensation current path (11) between the reference energy store (22) and the one or the plurality of battery cells (10 – 15) for measuring a voltage compensation current (A), wherein the voltage compensation current (A) matches the battery voltage and the reference voltage to one another, and a compensation current measuring device (21, 23, 25, 26) for measuring the voltage compensation current (A) is arranged in the compensation current path, wherein the self-discharge characterizing device is designed to derive the self-discharge and/or the battery state of the one or the plurality of battery cells (10 – 15) from a measured voltage compensation current (A).

Description

title

Self-discharge characterizing device and method for characterizing a self-discharge of energy storage devices

State of the art

This invention relates to a device for characterizing a

Self-discharge of one or more series-connected battery cells. Furthermore, the invention relates to a method for characterizing a self-discharge.

Battery cells are subject to a certain self-discharge, which manifests itself in the occurrence of a self-discharge current within the battery cell. One

Self-discharge current flows directly across the electrolyte and / or through a separating layer between an anode and a cathode of the battery, whereby aging, dendrites, contamination, production faults or external mechanical effects can influence, in particular increase, the self-discharge current. Cell delays and processes caused by aging increase this self-discharge current. Therefore, the self-discharge can be characterized via the self-discharge current. Self-discharge also lowers the voltage of the battery cell or battery. From a battery cell is due to the stored energy in principle a threat. The above states of cells resulting in increased self-discharge current may possibly lead to overheating and self-destruction of a battery, especially if the self-discharge current rises sharply. This can be serious

Have consequences. By characterizing the self-discharge, an increased self-discharge current can be detected in good time before the occurrence of a critical condition and the battery can be brought to a safe state. For example, the charging of the battery can be prevented or energy can be discharged from the battery. A direct measurement of the

Self-discharge current would be associated with an intrusion into the cell itself, which would require additional connections to the cell or additional sensors in the cell. Disclosure of the invention

According to the invention a Selbstentladungscharakterisiereinrichtung is proposed, with which the self-discharge and / or the battery state of one or more interconnected battery cells can be characterized. For this purpose, the Selbstentladungscharakterisiereinrichtung on a reference energy storage, which is charged with energy from the or the battery cells or other energy source. The reference energy storage and the battery cell are connected in parallel, wherein each of the positive poles and the

Negative poles of the reference energy storage and the battery cell

be interconnected or interconnected. Of the

References energy storage may be about a battery or preferably one

Be condenser, such as a supercapacitor or the like. In a particular embodiment, the reference energy storage has a lower one

Self-discharge than that of the battery cell, that is, its

Reference voltage without further action sinks less than the

Battery voltage. The reference energy storage may have a reference voltage that is at least approximately equal to a battery voltage of the one or more battery cells. Due to the self-discharge of the battery cells, the battery voltage drops after charging. This can be especially true in the

Comparison with the reference voltage the self-discharge and, derived from this, the battery condition can be characterized. Under certain circumstances, the sinks

Reference voltage, for example, if the reference energy storage also has a self-discharge, or if this energy is taken to supply the Selbstentladungscharakterisiereinrichtung. When power is taken to supply the self-discharge characteristic of the battery, the battery voltage decreases to an increased degree.

By a battery cell is meant in this patent application, in particular a rechargeable battery cell. The battery cell (s) are not part of the Selbstentladungscharakterisiereinrichtung, but their object of measurement. In this patent application will be discussed below for reasons of concise presentation of the invention of a battery cell, but always is the

Application of the invention to a plurality of battery cells and includes. In the Selbstentladungscharakterisiereinrichtung is between the

References energy storage and the one or more battery cells arranged a balancing current path. A voltage difference between the battery voltage and the reference voltage causes over the

Equalizing current path, a compensating current flows, which in turn causes the battery voltage and the reference voltage to equalize. The direction of the compensation current depends on which of the battery voltage and the reference voltage is higher. This in turn depends on the self-discharge or external discharge ratios of the two energy stores. The equalizing current in the equalizing current path can be determined by means of a compensating current measuring device, which in the

Balancing current path is arranged to be measured. For example, the compensating current measuring device has a shunt resistor, at which a voltage proportional to the compensating current can be tapped and measured; Other known methods of current measurement can also be used. The self-discharge current of the battery flows at any time in its interior. This constantly changes the electric charge of the

Battery cell (s) and thus also their battery voltage. The reference voltage may also change due to self-discharge; thus, the changes

Differential voltage between the battery voltage and the reference voltage at any time. The differential voltage drives the compensating current through the

Equalizing current path across the shunt resistor. This results in a time course of the compensation current, during which the compensating current approaches asymptotically to an end equalizing current, provided that there are no further influences. Such influences may affect the magnitude of the final equilibrium current or, if singular events, cause jumps in the asymptotic approach to a final state. By measuring the equalizing current at one or more times during or at the end of the described balancing process, increased self-discharge of the battery cell (s) can be detected by measuring the measured values and / or the timing of the compensating current with known values for defective and non-defective cells be compared.

The dependent claims show preferred developments of the invention. In one embodiment, the measurement of the compensation current may be digital and preferably by means of a microcontroller. Alternatively, it is conceivable in a further embodiment to carry out the characterization of the self-discharge by means of analog circuit technology.

In an exemplary embodiment, the characterization of the

Self-discharge at least approximately permanent. This can be useful, for example, for singular events in the battery.

In an alternative exemplary embodiment of the

Selbstentladungscharakterisiereinrichtung repeated this, the measurement of the compensation current several times after each time interval. This can be done by means of a switch in the current path of the

References energy storage is arranged to the battery and can be effected by closing, that the current flows in the current path and thus the self-discharge is characterized. The switch can be controlled, for example, by a microcontroller. This microcontroller can also do the

Characterize the self-discharge. An intermittent operation of the self-discharge characterizing device may be useful if a slowly developing increase in self-discharge occurs or is expected.

In a further embodiment, it is also conceivable to obtain information about the self-discharge of the battery from the asymptotic course of the compensation current. In particular, the current profile with a

stored standard current history are compared.

In a further embodiment of the self-discharge characterizing device, it is supplied with electrical energy from the reference energy store or from the battery cell or from a supply energy store which is separate from the reference energy store. To do that for the

Self-discharge characterizer to achieve required voltage level, this may be connected to a DC / DC converter, which adjusts the voltage level of the reference energy storage or or the battery cells or the supply energy storage thereto. In a further embodiment of the self-discharge characterizing means, the reference energy storage has less capacity than the one or more battery cells. As a result, only a small amount of charge is removed from the battery cell by the operation of the self-discharge characterizing device.

In a further aspect of the invention, a battery cell is proposed, which has a self-discharge characterizing device according to the invention according to one of the embodiments described above.

In a further aspect of the invention, a method is proposed, with which a self-discharge of the battery and / or a battery state is detected by means of one of the self-discharge characterizing devices described above. For this purpose, an electrical reference energy storage before detection is at least approximately brought to the same potential as the one or more battery cells. Then, by taking advantage of changes in the battery voltage and the reference voltage, the

Self-discharge and / or battery condition are detected. The self-discharge does not have to be explicitly recorded as current, but can also be characterized in the form of suitable data.

Hereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawings:

FIG. 1 shows a schematic circuit diagram of a first embodiment of a self-discharge characterizing device,

Figure 2 is a schematic circuit diagram of a second embodiment of the Selbstentladungscharakterisiereinrichtung.

Figure 1 shows schematically a circuit diagram of a

Self-discharge characterizing device 1 for measuring a

Self-discharge current of a battery cell 10. One terminal of the battery cell 10 is connected to ground potential 20. The other terminal of the battery cell 10 is connected via a shunt resistor 21 to a first terminal of the

References energy storage 22 connected. A second connection of the

References energy storage 22 is connected to ground potential 20 so that a Parallel connection of the battery cell 10 with the reference energy storage 22 is present. The reference energy storage 22 is connected to the battery cell 10 via a current path 11 in which a shunt resistor 21 is arranged. In order to be able to measure a voltage across the shunt resistor 21, its two terminals are each connected via connecting lines 25 and 26 with a

Voltage measuring device 23 is connected, which can measure a difference voltage between the connecting lines 25 and 26. Prior to detection of the self-discharge current, the reference energy storage 22 is brought to the voltage of the battery cell 10. After equalizing the voltages of the battery cell 10 and the balancing voltage source 22 discharges the

Battery cell 10 through the self-discharge current. This results in a voltage difference being created between the reference energy storage 22 discharging to a different extent, in particular considerably less, and the battery cell 10, by means of which a compensation current A is interposed between the energy supply

References energy storage 22 and the battery cell 10 and via the shunt

Resistor 21 flows. When the self-discharge of the reference energy storage 22 is lower than that of the battery cell 10, the equalizing current A flows through the current path 11 to the battery cell 10, as indicated by the arrow in FIG. 1. Between the connection lines 25 and 26 between the shunt resistors 21 and the voltage measuring device 23 results in a differential voltage corresponding to the equalizing current and the of the

Differential voltage detection device 23 is detected. The

Differential voltage detection device 23 is connected via a signal line 27 to a microcontroller 24 which receives the signals from the

Differential voltage detection device 23 evaluates and from the

Equalizing current A is the self-discharge current or a state of

Battery cell dissipates. The differential voltage detection device 23 may be, for example, a differential voltage amplifier, wherein on the

Signal line 27, the amplified voltage difference can be applied as a voltage. In the microcontroller 24, an analog-to-digital converter can be arranged, with which the amplified differential voltage is converted into digital data. As an alternative to a differential voltage amplifier, the differential voltage at the shunt can also be measured directly in the microcontroller. The digital data can be processed and converted into the self-discharge current or a state of the battery cell. In the current path 1 1, a switching device 35 can be arranged in a variant, which is shown in Figure 1, by means of which the flow of current through the current path 1 1 is interruptible. By means of Switching device can be an intermittent characterization of

Self-discharge can be effected by the switching device 35 allows the current flow only for a single, time-limited characterization. In another, not shown variant, the switching device 35 is missing in the current path 1 1. In particular, if a continuous characterization of

Self-discharge is desired, the switching device 35 can be omitted.

FIG. 2 schematically shows a circuit diagram of a second embodiment of the self-discharge characterizing device, which in essential parts of the first embodiment

Embodiment is the same. Like features and elements are designated by like reference numerals and will not be described again separately. Reference is made to the comments on Figure 1. 2, instead of just one battery cell 10, a series connection of battery cells 10 - 15 is shown whose self-discharge or state is to be detected. Both variants are for everyone

Embodiments conceivable. The second embodiment includes the first embodiment and extends it to the features and functions described below. For the power supply of the microcontroller 24, an additional third energy source 30 is provided. This is connected with one connection to the ground potential 20 and with a second connection to one

Charging connection 32 to the not connected to the ground potential 20 terminal of the battery cells 10 - 15 connected. In the charging connection 32, a charging switch 31 is arranged, which is preferably designed as a semiconductor switch. The control terminal of the semiconductor switch serving as a charging switch 31 is connected to the microcontroller 24 via a control line 34. Of the

Microcontroller 24 can thus trigger the charging of the third energy source 30 by switching on the charging switch 31 via the control line 34. Then, the potentials of the battery cells 10-15 and the third power source 30 at the terminals connected to the connection line 32 are made equal. In this case, a charging current L flows from the battery cells 10-15 to the third energy source 30. To the charging line 32, a DC / DC converter 29 may also be connected, which adapts the voltage of the third power source 30 to the voltage required by the microcontroller 24. Of the

Microcontroller can thus switch through the charging switch 31 at appropriate time intervals, whereby each of the third power source 30 is charged. The

Battery cells 10-15 are thus only temporarily charged by the charging of the third energy source 30. During this time, for example, measuring be exposed to the compensation current A. The DC / DC converter 29 is connected to the microcontroller 24 via a power supply line 28.

Claims

claims

1 . Self-discharge characterizing means (1) for one or more

interconnected battery cell (s) (10 - 15),

characterized in that the

Selbstentladungscharakterisiereinrichtung (1) an electrical

A reference energy store (22) providing a reference voltage and chargeable with energy from the battery cell (s) (10 -15), wherein after charging, the reference voltage is at least approximately equal to a battery voltage of the one or more battery cell (s). (10 - 15), and the

Selbstentladungscharakterisiereinrichtung is adapted to, at a time after charging the reference energy storage (22)

Changes in battery voltage and reference voltage to

Use of the purpose of detecting a self-discharge of the battery cell (s) (10 - 15) and / or a state of the battery cell (s) (10 - 15), wherein the Selbstentladungscharakterisiereinrichtung a compensation current path (1 1) between the reference energy storage (22) and the one or more battery cells (10-15) for measuring a

Voltage equalizing current (A), wherein the

Voltage compensation current (A) the battery voltage and the

Equalizes reference voltage, and

in the equalizing current path, a compensating current measuring means (21, 23, 25, 26) for measuring the voltage equalizing current (A) is arranged, the self-discharging characterizing means being arranged to derive from a measured voltage equalizing current (A)

Discharge self and / or the battery state of the one or more battery cell (s) (10 - 15).

2. self-discharge characterizing device (1) according to claim 1,

characterized in that the

Selbstentladungscharakterisiereinrichtung (1) is adapted to repeat the measurement of the compensation current (A) after time intervals several times and thus measured a temporal current profile of the Equalizing current (A) for determining a self-discharge of

Battery cell (s) (10 - 15) and / or battery condition.

Self-discharge characterizing device (1) according to one of

preceding claims, characterized in that the

Energy supply of the Selbstentladungscharakterisiereinrichtung (1) from the reference energy storage 22 or from the or the battery cell (s) (10 - 15) or from one or the battery cell (s) (10 - 15) rechargeable supply energy storage is carried out, in particular via a DC / DC Walker (46).

Self-discharge characterizing device (1) according to one of

preceding claims, wherein the reference energy storage (22) has less capacity than the battery cell (s) (10-15).

Battery cell (10-15) having a self-discharge characterizing device (1) according to one of the preceding claims, by means of which the

Self-discharge and / or the state of the battery cell (s) (10-15) is detectable.

Method for characterizing a self-discharge and / or a battery state of one or more battery cells (10 - 15) by means of a self-discharge characterizing device (1) according to one of claims 1 to 6, wherein the reference energy store (22) at least

approximately the same potential as the battery cell (s) (10 to 15) is brought and used to characterize the self-discharge and / or the battery state of the one or more battery cell (s) (10-15) changes in the battery voltage and the reference voltage by measuring a compensating current (A) and from that the

Self-discharge and / or the battery state of the one or more battery cell (s) (10 - 15) is derived.