DE102016014617A1 - Method for operating a battery - Google Patents

Abstract

The invention relates to a method for operating a battery (14) having a plurality of cells (16, 18, 20), of which at least one cell (16, 18, 20) has an unknown cell voltage, wherein at least one substitute value for the unknown cell voltage is determined by means of a Battery model is determined and that by means of the battery (14) taking into account the substitute value power is provided if the substitute value is within a tolerance range (22).

Description

The invention relates to a method for operating a battery.

From the DE 10 2010 062 187 A1 For example, there is known a method for determining an open-circuit voltage of a battery which changes, for example due to aging, in which the open-circuit voltage is determined when the battery is charged. On the basis of a measurement of individual voltages of cells of the battery, a state estimation regarding a state of charge and an aging state is carried out.

If individual voltages of certain cells of a battery can not be determined, for example due to an accident and / or due to wear, operation of the battery is usually discontinued. In the case of a powered by the battery vehicle this must be temporarily shut down accordingly.

The invention is in particular the object of providing a method with advantageous properties in terms of reliable operation. It is achieved by a method according to the invention according to claim 1. Further developments of the invention will become apparent from the dependent claims.

The invention relates to a method for operating a battery, in particular to an at least partial power supply of a particular at least partially driven by electric motor vehicle, especially a motor vehicle, especially in at least one accident, especially in at least one accident mode, with multiple cells, of which at least one Cell has an unknown cell voltage.

It is proposed that at least one substitute value for the unknown cell voltage is determined on the basis of a battery model, and that power is provided, in particular for a drive of the vehicle, taking into account the substitute value, if the substitute value is within a tolerance range.

Advantageously, the battery has at least one battery pack, which comprises the cells. Particularly advantageously, at least some or all cells are connected in series. Preferably, in a normal operating state, a cell voltage is determined for each cell, in particular by means of and / or by at least one cell monitoring circuit. Preferably, the cell monitoring circuit is connected via corresponding lines to cell poles of the cells. In particular, the cell monitoring circuit is provided for monitoring and / or measuring the cell voltages and / or at least one cell temperature. Particularly preferably, in the normal operating state, an operating voltage of the battery is determined on the basis of the cell voltages, in particular as the sum of the cell voltages. It is conceivable that the method comprises the normal operating mode. In particular, the method may be provided for operation of the battery in the accident mode operating state and, advantageously, additionally in the normal operating state. By "provided" is intended to be understood in particular specially programmed, designed and / or equipped. The fact that an object is intended for a specific function should in particular mean that the object fulfills and / or executes this specific function in at least one application and / or operating state. By "providing" a method for a purpose, it should be understood, in particular, that the method includes at least one method step specifically aimed at the purpose and / or that the method is specifically directed to the purpose and / or that the method serves a fulfillment of the purpose and is at least partially optimized for this fulfillment. By "providing" a method step for a purpose, it should be understood, in particular, that the method step specifically aims at the purpose and / or that the method step is directed specifically to the purpose and / or that the method step serves to fulfill the purpose, and is at least partially optimized towards this fulfillment.

In particular, the unknown cell voltage is unknown due to the accident. For example, the accident may include an interruption between the cell monitoring circuit and the cell with the unknown cell voltage, in particular an interruption due to vibration, due to shock, due to shock, due to material expansion, due to temperature differences, due to mechanical stress or due to other occurring in particular external or age-related causes. Furthermore, it is conceivable that a contact with several cells is interrupted and / or several cells have unknown cell voltages, for example also due to a failure and / or damage of individual integrated circuits of the cell monitoring circuit, which in particular monitor a certain number of cells in the normal operating state.

Advantageously, the replacement value in the operation of the battery is processed and / or treated analogously to an available cell voltage value. Preferably, the tolerance range includes a safe operating range. The tolerance range particularly preferably comprises an upper critical operating range and / or a lower critical range Operating range. In particular, the tolerance range extends over a voltage range between an upper safety limit and a lower safety limit. In particular, provision of power is interrupted if the substitute value is outside the tolerance range, in particular above or below the upper or lower safety limit.

Advantageous properties with regard to operation of a battery can be achieved by the method according to the invention. In particular, a robustness of a battery can be achieved in the event of failure of a cell voltage measurement. Furthermore, a frequency of breakdowns and / or a risk of a vehicle being stuck can be reduced. In addition, a possibility may be provided to bring a vehicle with a partially defective power supply to a workshop. In particular, the method can be applied inexpensively to existing batteries. It is advantageously possible to retrofit existing energy supply geometries and / or batteries. In addition, advantageous properties can be achieved with regard to a gentle treatment of available resources.

In an advantageous embodiment of the invention, it is proposed that in at least one method step the substitute value be determined as the difference between a known battery pack voltage and a sum of available known cell voltages of the battery, in particular in the case of a single unknown cell voltage. In particular, the battery model in this case includes a consideration of a voltage of the battery based on individual cell voltages. As a result, a quick determination of a replacement value can be made possible.

In a further embodiment of the invention, it is proposed that the substitute value is determined on the basis of a last available charge state of the cell and on the basis of a current pack current, in particular in the case of a plurality of unknown cell voltages of a plurality of cells. In particular, replacement values for a plurality of unknown cell voltages of a plurality of cells are determined. In the normal operating state and / or in the accident operating state, the cell monitoring circuit preferably determines the state of charge of the cell and, in particular, the state of charge of several, in particular of all cells. Advantageously, the battery model in this case comprises further parameters of the battery and / or at least some or all cells, for example at least one capacitor and / or at least one impedance and / or at least one electrical resistance and / or at least one temperature or the like. As a result, a transitional operation of the battery can be made possible for different failures.

Advantageous stable operation characteristics can be achieved with a vehicle having a control unit provided for performing the method of operating a battery. In particular, the vehicle has the battery. Advantageously, the vehicle, in particular the control unit, the cell monitoring circuit.

Further advantages will become apparent from the following description of the figures. In the figures, an embodiment of the invention is shown. The figures, the description of the figures and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Showing:

1 a vehicle having a control unit, which is provided for carrying out a method for operating a battery of the vehicle,

2 a schematic flow diagram of the method for operating the battery and

3 a schematic representation of a tolerance range for a determined by the method substitute value of a cell voltage.

The 1 shows a vehicle 10 with a battery 14 and with an electric motor 26 which is in a normal operating condition from the battery 14 is energized. The battery 14 includes several cells 16 . 18 . 20 of which, for reasons of clarity, only three are provided with reference numerals. Multiple cells 16 . 18 . 20 the battery 14 are each connected in series and form a pack of the battery 14 , Furthermore, in each case one pack of the battery is in the present case 14 in each case via a supply line with the electric motor 26 connected. It is of course also conceivable that the battery 14 includes exactly one pack. The vehicle 10 has a control unit 12 which comprises a cell monitoring circuit, not shown in detail, connected to the cells 16 . 18 . 20 the battery 14 connected is. The cell monitoring circuit is designed to provide parameters such as a cell voltage, a pack voltage, a pack current, a state of charge of cells 16 . 18 . 20 , a capacity of cells 16 . 18 . 20 and / or to determine and / or query a temperature.

The control unit 12 is intended to provide a method of operating the battery 14 perform, wherein at least one of the cells 16 . 18 . 20 has at least one unknown cell voltage. This may be the case, for example, in an accident as described above. The method is then executed in a fault mode. In particular, in the event of a fault, a single cell voltage or cell voltages of several cells may be unknown, for example due to aging of the battery. According to the method, a substitute value for the unknown cell voltage is determined on the basis of a battery model and by means of the battery 14 provided the replacement value is provided, provided that the replacement value is within a tolerance 22 lies (cf. 3 ). With the aid of the provided power, the electric motor can initially continue to be operated in the event of a fault, in order, for example, to be able to approach a workshop.

The 2 shows a schematic flow diagram of the method. In a first process step 28 it is determined whether a cell voltage or several cell voltages can not currently be determined. If all cell voltages can be determined, the check is successfully completed. The method may, if necessary, include a restart of the check, for example a check at regular intervals. If one or more cell voltages are unknown and / or not determinable, in particular by the cell monitoring circuit, in a second method step 30 First, a last available value for the now unknown cell voltage checked. If this value is outside the tolerance range 22 , becomes an operation of the battery 14 in a third process step 32 completed. The vehicle 10 is shut down for security reasons, for example. If this value is within the tolerance range 22 , becomes in a fourth process step 34 checks how many cell voltages are unknown.

Is a single cell voltage, especially the battery 14 or also the pack, unknown, becomes in a fifth process step 24 the substitute value U _Substitute as the difference from a known pack voltage U _{Pack of} the battery 14 and a sum of available known cell voltages U _{Cell, i of} the battery 14 certainly. In particular, several unknown cell voltages for different packs can also be determined simultaneously in this way. For example, let's say the number of cells 16 . 18 . 20 the battery 14 or the corresponding pack of the battery 14n and the cell with the unknown cell voltage is indicated by the index m. In this case, the substitute value can be determined as

U _substitutes can have a certain error ΔU _error . To take this into account, the substitute value in a sixth step 52 output. In a seventh process step 54 It is checked whether U _{substitutes are} within the tolerance range 22 and whether, if necessary, a new replacement value calculation is necessary, for example, during continued operation of the battery 14 or the vehicle 10 , Like in the 3 shown includes the tolerance range 22 a safe operating area 36 , an upper critical operating range 38 , a lower critical operating range 40 , an upper safety limit 42 , a lower safety limit 44 , as well as areas 46 . 48 out of tolerance 22 , In the present case, an operation of the battery 14 only continued if U _substitutes + ΔU _error <U _{critical, upper} and U _Substitute - ΔU _Error U _{critical, lower} , where U _{crttical, upper} and U _{critical, lower} the lower safety _limit 44 and the upper safety limit 42 describe. Of course, it is conceivable to incorporate further methods for calculating an error.

Furthermore, the method is provided, replacement values for a plurality of unknown cell voltages of a plurality of cells 16 . 18 . 20 to investigate. In particular, in this case, in an eighth process step 50 the substitute value, in particular the substitute values, based on a last available charge state of the cell 16 . 18 . 20 , especially the cells 16 . 18 . 20 , and based on a current _pack current I _Pack determined. However, it is also conceivable substitute values always as for the eighth process step 50 described to determine. A determination according to the fifth method step 24 however, offers the advantage of rapid detection in the case of a single unknown cell voltage.

In the eighth process step 50 Unavailable cell voltages are determined from the battery model, which in this case is information regarding a capacity of cells 16 . 18 . 20 , a pack current I _pack , a state of charge of cells, an internal resistance, a physical and / or electrical position and / or an arrangement of cells and / or a temperature. The battery model in this case is based in particular on the fact that, starting from a last stored cell voltage, the substitute value is determined on the basis of a current which flows through the cell. The mentioned additional parameters can be used to improve a quality of the model.

Starting from the last stored cell voltage, the cell with the unknown cell voltage is assigned a charge state SOC. It is conceivable that the SOC is directly available as a separate value and / or determined by the cell monitoring circuit. Based on the SOC, it is possible to determine which amount of charge is currently in the cell.

Now lies for a calculation _cycle t _{cycle of} the eighth process step 50 for example, 10 ms, a current of I _pack, for example, 20 A, so must be deducted from this amount of charge 200 mAs, all of which are to be understood by way of example only. An SOC (n) to be determined in an n-th calculation cycle can thus be determined as SOC (n) = SOC (n-1) -t _cylce * I _pack , where SOC (n-1) identifies the last detected SOC. Based on some or all of the above-mentioned further cell data, for example based on an impedance, the substitute value can be determined from the new SOC (n).

Analogous to the case of the fifth method step 24 then becomes the sixth and seventh process step 52 and 54 carried out. This can be done in parallel in particular for several cells with unknown cell voltages. In particular, in the case of a precise battery model can be the tolerance range 22 be chosen small. It is also conceivable, the tolerance range 22 to choose temporally changeable. For example, the tolerance range 22 be increased continuously and / or graduated during the Störbetriebbetriebszustands to take into account, for example, aufaddierenden calculation errors.

LIST OF REFERENCE NUMBERS

10

vehicle

12

control unit

14

battery

16

cell

18

cell

20

cell

22

tolerance

24

step

26

electric motor

28

step

30

step

32

step

34

step

36

operating range

38

operating range

40

operating range

42

safety limit

44

safety limit

46

Area

48

Area

50

step

52

step

54

step

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010062187 A1 [0002]

Claims (5)

Method for operating a battery ( 14 ) with several cells ( 16 . 18 . 20 ), of which at least one cell ( 16 . 18 . 20 ) has an unknown cell voltage, characterized in that at least one substitute value for the unknown cell voltage is determined on the basis of a battery model and that by means of the battery ( 14 ) is provided, taking into account the substitute value, provided that the substitute value is within a tolerance ( 22 ) lies. Method according to claim 1, characterized in that in at least one method step ( 24 ) the substitute value as the difference from a known battery pack voltage ( 14 ) and a sum of available known cell voltages of the battery ( 14 ) is determined. Method according to claim 1 or 2, characterized in that the substitute value is determined on the basis of a last available charge state of the line ( 16 . 18 . 20 ) and based on a current pack current. Method according to one of the preceding claims, characterized in that substitute values for a plurality of unknown cell voltages of a plurality of cells ( 16 . 18 . 20 ) be determined. Vehicle ( 10 ) with at least one control unit ( 12 ), which is provided for carrying out a method according to one of the preceding claims.

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