BATTERY SYSTEM FOR AN ELECTRIC VEHICLE, METHOD FOR DIAGNOSING A BATTERY SYSTEM, AND ELECTRIC VEHICLE

Abstract

The invention relates to a battery system (10) for an electric vehicle, comprising a battery pack (5) having a positive pole (22), a negative pole (21), at least one battery cell (2) and a pack voltage divider (25), and comprising at least one coupling network having a negative terminal (11) and a positive terminal (12), wherein the pack voltage divider (25) comprises a positive pack resistor (RP2) and a positive sub-pack-resistor (RSP2) which are connected to one another in series between the positive pole (22) and a reference point (50), and a negative pack resistor (RP1) and a negative sub-pack-resistor (RSP1) which are connected to one another in series between the negative pole (21) and the reference point (50). The at least one coupling network comprises a coupling voltage divider (15) having a positive coupling resistor (RK2) and a positive sub-coupling-resistor (RSK2) which are connected to one another in series between the positive terminal (12) and the reference point (50), and having a negative coupling resistor (RK1) an a negative sub-coupling-rcsistor (RSK1) which are connected to one another in series between the negative terminal (11) and the reference point (50). The invention also relates to a method for diagnosing a battery system (10) according to the invention, wherein a positive pack voltage (UP2) falling at the positive sub-pack-resistor (RSP2) is measured, a negative pack voltage (UP1) falling at the negative sub-pack-rcsistor (RSP I) is measured, a positive coupling voltage (UK2) falling at the positive sub-coupling-resistor (RSK2) is measured, a negative coupling voltage (UK1) falling at the negative sub-coupling-resistor (RSK1) is measured, and an evaluation of the measured voltages (UP1, UP2, UK1, UK2) is carried out. The invention also relates to an electric vehicle comprising a battery system (10) according to the invention.

Claims

1. A battery system (10) for an electric vehicle, comprising a battery pack (5), which has a positive pole (22), a negative pole (21), at least one battery cell (2) and a pack voltage divider (25), and at least one coupling power supply system, which has a negative terminal (11) and a positive terminal (12), wherein the pack voltage divider (25) comprises a positive pack resistance (RP2) and a positive sub-pack resistance (RSP2), which are connected in series with one another between the positive pole (22) and a reference point (50), and a negative pack resistance (RP1) and a negative sub-pack resistance (RSP1), which are connected in series with one another between the negative pole (21) and the reference point (50), characterized in that the at least one coupling power supply system has a coupling voltage divider (15), which comprises a positive coupling resistance (RK2) and a positive sub-coupling resistance (RSK2), which are connected in series with one another between the positive terminal (12) and the reference point (50), and a negative coupling resistance (RK1) and a negative sub-coupling resistance (RSK1), which are connected in series with one another between the negative terminal (11) and the reference point (50).

2. The battery system (10) as claimed in claim 1, characterized in that the positive pole (22) is connectable to the positive terminal (12) by means of a positive pack switch (SP2), and/or in that the negative pole (21) is connectable to the negative terminal (11) by means of a negative pack switch (SP1).

3. The battery system (10) as claimed in either of the preceding claims, characterized in that a resistance ratio of the pack voltage divider (25) differs from a resistance ratio of the coupling voltage divider (15).

4. The battery system (10) as claimed in one of the preceding claims, characterized in that the pack voltage divider (25) comprises a positive measuring switch (SM2), by means of which the positive pack resistance (RP2) and the positive sub-pack resistance (RSP2) are disconnectable from the positive pole (22) or the reference point (50), and/or a negative measuring switch (SM1), by means of which the negative pack resistance (RP1) and the negative sub-pack resistance (RSP1) are disconnectable from the negative pole (21) or the reference point (50).

5. The battery system (10) as claimed in one of the preceding claims, further comprising a charging power supply system, which has a positive charging connection (32), a negative charging connection (31) and a charging voltage divider (35), wherein the charging voltage divider (35) comprises a positive charging resistance (RL2) and a positive sub-charging resistance (RSL2), which are connected in series with one another between the positive charging connection (32) and the reference point (50), and a negative charging resistance (RL1) and a negative sub-charging resistance (RSL1), which are connected in series with one another between the negative charging connection (31) and the reference point (50).

6. The battery system (10) as claimed in claim 5, characterized in that the positive charging connection (32) is connectable to the positive terminal (12) by means of a positive charging switch (SL2), and/or in that the negative charging connection (31) is connectable to the negative terminal (11) by means of a negative charging switch (SL1).

7. The battery system (10) as claimed in either of claims 5 to 6, characterized in that a resistance ratio of the charging voltage divider (35) differs from a resistance ratio of the pack voltage divider (25).

8. The battery system (10) as claimed in one of claims 5 to 7, characterized in that a resistance ratio of the charging voltage divider (35) differs from a resistance ratio of the coupling voltage divider (15).

9. A method for diagnosing a battery system (10) as claimed in one of the preceding claims, wherein a positive pack voltage (UP2) in the form of a voltage drop across the positive sub-pack resistance (RSP2) is measured, a negative pack voltage (UP1) in the form of a voltage drop across the negative sub-pack resistance (RSP1) is measured, a positive coupling voltage (UK2) in the form of a voltage drop across the positive sub-coupling resistance (RSK2) is measured, a negative coupling voltage (UK1) in the form of a voltage drop across the negative sub-coupling resistance (RSK1) is measured, and an evaluation of the measured voltages (UP1, UP2, UK1, UK1) is performed.

10. An electric vehicle, comprising a battery system (10) as claimed in one of claims 1 to 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Embodiments of the invention will be explained in more detail with reference to the drawing and the description below.

[0037] In the drawing:

[0038] FIG. 1 shows a schematic illustration of a battery system.

DETAILED DESCRIPTION

[0039] In the description below relating to the embodiments of the invention, identical or similar elements are denoted by the same reference symbols, wherein a repeated description of these elements in individual cases has not been provided. The FIGURES represent the subject matter of the invention merely schematically.

[0040] FIG. 1 shows a schematic illustration of a battery system 10 for an electric vehicle. The battery system 10 comprises a battery pack 5, which has a positive pole 22, a negative pole 21 and a plurality of battery cells 2. The battery cells 2 are in this case connected in series between the positive pole 22 and the negative pole 21. A system voltage Us which is provided by the battery cells 2 connected in series is present between the poles 21, 22 of the battery pack 5. The system voltage Us is 400 V, for example.

[0041] The battery system 10 also comprises a coupling power supply system. The coupling power supply system has a negative terminal 11 and a positive terminal 12. The coupling power supply system is used in particular for connecting the battery system 10 to a vehicle power supply system of the electric vehicle. The coupling power supply system also has a DC-link capacitor CL, which is connected between the positive terminal 12 and the negative terminal 11.

[0042] The battery system 10 comprises a positive pack switch SP2 and a negative pack switch SP1. The positive pole 22 is connectable to the positive terminal 12 and disconnectable from the positive terminal 12 by means of the positive pack switch SP2. The negative pole 21 is connectable to the negative terminal 11 and disconnectable from the negative terminal 11 by means of the negative pack switch SP1. Therefore, the battery pack 5 can be electrically connected to the coupling power supply system and disconnected from the coupling power supply system by means of the pack switches SP1, SP2.

[0043] The pack switches SP1, SP2 are in the form of electromechanical relays or contactors, for example. In particular, the two pack switches SP1, SP2 can together form a two-pole relay or contactor.

[0044] The battery system 10 further comprises a charging power supply system. The charging power supply system has a positive charging connection 32 and a negative charging connection 31. The charging power supply system is used in particular for charging the battery cells 2 of the battery pack 5 by means of an external charger.

[0045] The battery system 10 comprises a positive charging switch SL2 and a negative charging switch SL1. The positive charging connection 32 is connectable to the positive terminal 12 and disconnectable from the positive terminal 12 by means of the positive charging switch SL2. The negative charging connection 31 is connectable to the negative terminal 11 and disconnectable from the negative terminal 11 by means of the negative charging switch SL1. Therefore, the charging power supply system can be electrically connected to the coupling power supply system and disconnected from the coupling power supply system by means of the charging switches SL1, SL2.

[0046] The charging switches SL1, SL2 are in the form of electromechanical relays or contactors, for example. In particular, the two charging switches SL1, SL2 can together form a two-pole relay or contactor.

[0047] The battery pack 5 has a pack voltage divider 25. The pack voltage divider 25 comprises a positive pack resistance RP2 and a positive sub-pack resistance RSP2 as well as a negative pack resistance RP1 and a negative sub-pack resistance RSP1. The positive pack resistance RP2 and the positive sub-pack resistance RSP2 are connected in series with one another between the positive pole 22 and a reference point 50. The negative pack resistance RP1 and the negative sub-pack resistance RSP1 are connected between the negative pole 21 and the reference point 50.

[0048] The pack voltage divider 25 further comprises a positive measuring switch SM2 and a negative measuring switch SM1. The positive measuring switch SM2 is connected in series with the positive pack resistance RP2 and the positive sub-pack resistance RSP2. The negative measuring switch SM1 is connected in series with the negative pack resistance RP1 and the negative sub-pack resistance RSP1. The positive pack resistance RP2 and the positive sub-pack resistance RSP2 are in this case disconnectable from the positive pole 22 and connectable to the positive pole 22 by means of the positive measuring switch SM2. The negative pack resistance RP1 and the negative sub-pack resistance RSP1 are disconnectable from the negative pole 21 and connectable to the negative pole 21 by means of the negative measuring switch SM1.

[0049] The measuring switches SM1, SM2 are, for example, in the form of switchable transistors, in particular field-effect transistors, for example MOSFETs.

[0050] When the positive measuring switch SM2 is closed, a positive pack voltage UP2 forms as a voltage drop across the positive sub-pack resistance RSP2, and this positive pack voltage UP2 is measured by a measuring channel (not illustrated here). When the negative measuring switch SM1 is closed, a negative pack voltage UP1 forms as a voltage drop across the negative sub-pack resistance RSP1, and this negative pack voltage UP1 is measured by a measuring channel (not illustrated here). The sum of the positive pack voltage UP2 and the negative pack voltage UP1 corresponds, by means of a conversion, to the system voltage Us, which is present between the poles 21, 22 of the battery pack 5. In this case, the conversion is performed taking into consideration the ratio between the positive pack resistance RP2 and the positive sub-pack resistance RSP2 and the ratio between the negative pack resistance RP1 and the negative sub-pack resistance RSP1.

[0051] The coupling power supply system has a coupling voltage divider 15. The coupling voltage divider 15 comprises a positive coupling resistance RK2 and a positive sub-coupling resistance RSK2 as well as a negative coupling resistance RK1 and a negative sub-coupling resistance RSK1. The positive coupling resistance RK2 and the positive sub-coupling resistance RSK2 are connected in series with one another between the positive terminal 12 and the reference point 50. The negative coupling resistance RK1 and the negative sub-coupling resistance RSK1 are connected in series with one another between the negative terminal 11 and the reference point 50.

[0052] A positive coupling voltage UK2 forms as a voltage drop across the positive sub-coupling resistance RSK2, and this positive coupling voltage UK2 is measured by a measuring channel (not illustrated here). A negative coupling voltage UK1 forms as a voltage drop across the negative sub-coupling resistance RSK1, and this negative coupling voltage UK1 is measured by a measuring channel (not illustrated here). The sum of the positive coupling voltage UK2 and the negative coupling voltage UK1 corresponds, by means of a conversion, to a voltage which is present between the terminals 11, 12. In this case, the conversion is performed taking into consideration the ratio between the positive coupling resistance RK2 and the positive sub-coupling resistance RSK2 and the ratio between the negative coupling resistance RK1 and the negative sub-coupling resistance RSK1.

[0053] When the pack switches SP1, SP2 are closed, the voltage which is present between the terminals 11, 12 corresponds to the system voltage Us, which is present between the poles 21, 22 of the battery pack 5.

[0054] The charging power supply system has a charging voltage divider 35. The charging voltage divider 35 comprises a positive charging resistance RL2 and a positive sub-charging resistance RSL2 as well as a negative charging resistance RL1 and a negative sub-charging resistance RSL1. The positive charging resistance RL2 and the positive sub-charging resistance RSL2 are connected in series with one another between the positive charging connection 32 and the reference point 50. The negative charging resistance RL1 and the negative sub-charging resistance RSL1 are connected in series with one another between the negative charging connection 31 and the reference point 50.

[0055] A positive charging voltage UL2 forms as a voltage drop across the positive sub-charging resistance RSL2, and this positive charging voltage UL2 is measured by a measuring channel (not illustrated here). A negative charging voltage UL1 forms as a voltage drop across the negative sub-charging resistance RSL1, and this negative charging voltage UL1 is measured by a measuring channel (not illustrated here). The sum of the positive charging voltage UL2 and the negative charging voltage UL1 corresponds, by means of a conversion, to a voltage which is present between the charging connections 31, 32. In this case, the conversion is performed taking into consideration the ratio between the positive charging resistance RL2 and the positive sub-charging resistance RSL2 and the ratio between the negative charging resistance RL1 and the negative sub-charging resistance RSL1.

[0056] When the pack switches SP1, SP2 and the charging switches SL1, SL2 are closed, the voltage which is present between the charging connections 31, 32 corresponds to the system voltage Us, which is present between the poles 21, 22 of the battery pack 5.

[0057] The positive pack resistance RP2 in this case has a value of 5 MΩ. The positive sub-pack resistance RSP2 in this case has a value of 50 kΩ. The negative pack resistance RP1 in this case has a value of 5 MΩ. The negative sub-pack resistance RSP1 in this case has a value of 50 kΩ. A resistance ratio of the pack voltage divider 25 approximately corresponds to a ratio of the positive pack resistance RP2 to the negative pack resistance RP1. In this case, the resistance ratio of the pack voltage divider 25 is therefore:

RP2/RP1=5/5=1

[0058] The positive coupling resistance RK2 in this case has a value of 7 MΩ. The positive sub-coupling resistance RSK2 in this case has a value of 70 kΩ. The negative coupling resistance RK1 in this case has a value of 3 MΩ. The negative sub-coupling resistance RSK1 in this case has a value of 30 kΩ. A resistance ratio of the coupling voltage divider 15 approximately corresponds to a ratio of the positive coupling resistance RK2 to the negative coupling resistance RK1. In this case, the resistance ratio of the coupling voltage divider 15 is therefore:

RK2/RK1≈7/3 2.333

[0059] The positive charging resistance RL2 in this case has a value of 6 MΩ. The positive sub-charging resistance RSL2 in this case has a value of 60 kΩ. The negative charging resistance RL1 in this case has a value of 4 MΩ. The negative sub-charging resistance RSL1 in this case has a value of 40 kΩ. A resistance ratio of the charging voltage divider 35 approximately corresponds to a ratio of the positive charging resistance RL2 to the negative charging resistance RL1. In this case, the resistance ratio of the charging voltage divider 35 is therefore:

RL2/RL1=6/4=1.5

[0060] The resistance ratio of the pack voltage divider 25, the resistance ratio of the coupling voltage divider 15 and the resistance ratio of the charging voltage divider 35 therefore each differ from one another.

[0061] The invention is not restricted to the exemplary embodiments described here and the aspects highlighted therein. Rather, a multiplicity of modifications which are within the scope of a person skilled in the art is possible within the scope set forth in the claims.