METHOD FOR OPERATING A BATTERY SYSTEM

Abstract

A method for operating a battery system with a plurality of cells, a battery system, a vehicle including such a battery system and a computer program element for operating such a battery system. The method for operating a battery system includes monitoring a state of health of each of the plurality of cells, detecting at least one malfunctioning cell, analysing the state of health of the malfunctioning cell, limiting a discharge power over a time period if the malfunctioning cell has a worst state of health in the battery system or limiting a charge power over a time period if the malfunctioning cell has a best state of health in the battery system, and reducing a minimum state of charge of the battery system over the time period.

Claims

1. A method for operating a battery system with a plurality of cells, comprising: monitoring a state of health of each of the plurality of cells; detecting at least one malfunctioning cell; analysing the state of health of the malfunctioning cell; limiting a discharge power over a time period if the malfunctioning cell has a worst state of health in the battery system or limiting a charge power over a time period if the malfunctioning cell has a best state of health in the battery system; and reducing a minimum state of charge of the battery system over the time period.

2. The method according to claim 1, further comprising evaluating a trend of the state of health of each of the plurality of cells.

3. The method according to claim 2, further comprising limiting a charge or discharge power and a charge or discharge maximum time, if the malfunctioning cell has a worst trend of state of health in the battery system.

4. The method according to claim 1, further comprising allowing driving to an end of a driving cycle.

5. The method according to claim 1, further comprising turning off a cell balancing unit to maintain differences of the state of health of the cells at a status before a malfunction occurs.

6. The method according to claim 1, monitoring a state of health comprising monitoring a cell capacity, a cell resistance and/or a cell self-discharge rate.

7. The method according to claim 2, evaluating a trend of the state of health comprising monitoring a cell capacity, a cell resistance and/or a cell self-discharge rate per a time unit.

8. The method according to claim 1, the malfunction of the cell being detected based on at least one lost or corrupted voltage signal.

9. The method according to claim 1, the malfunction being based on a fault in a voltage sense wire, in a battery monitoring system and/or a lost communication in the battery monitoring system.

10. A battery system, comprising: a plurality of cells; and a control unit, the control unit being configured for: monitoring a state of health of each of the plurality of cells, detecting at least one malfunctioning cell, analysing the state of health of the malfunctioning cell, and limiting a discharge power over a time period if the malfunctioning cell has a worst state of health in the battery system or limiting a charge power over a time period if the malfunctioning cell has a best state of health in the battery system.

11. The battery system according to claim 10, being configured to operate without interruption even a malfunctioning cell.

12. The battery system according to claim 10, wherein the control unit comprises a processing element configured for executing instructions stored in a memory.

13. A vehicle comprising the battery system according to claim 10, the vehicle being a battery electric vehicle (BEV), a plug-in-hybrid electric vehicle (PHEV) and/or a hybrid electric vehicle (HEV).

14. The vehicle according to claim 13, being configured to block starting the vehicle after a time period is expired, in case of a malfunctioning cell in the battery system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Exemplary embodiments of the disclosure will be described in the following with reference to the following drawings:

[0033] FIG. 1 shows schematically and exemplarily an embodiment of a battery system according to the present disclosure.

[0034] FIG. 2 shows schematically and exemplarily an embodiment of a method for operating a battery system with a plurality of cells according to the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0035] FIG. 1 shows a battery system 1 including a plurality of cells 10. The battery system 1 may be integrated in an electric vehicle such as battery electric vehicle (BEV), a plug-in-hybrid electric vehicle (PHEV) and/or a hybrid electric vehicle (HEV). To supply power for driving the electric vehicle, the battery system 1 requires the plurality of cells 10 connected in series or parallel to each other.

[0036] The battery system 1 further includes a battery monitoring system (BMS) 30 for monitoring a voltage of each cell 10 continuously, which are connected to the BMS 30 by voltage sense wires 20 via a connector 40. The battery system 1 also includes a control unit, which may be integrated in the BMS 30 or a separate component of the battery system 1. The control unit is configured to continuously monitor a state of health of each cell 10 and perform a countermeasure in case of a voltage signal loss.

[0037] The battery system 1 may have a defect on the voltage sense wire 20, welding spots 50 of the voltage sense wire 20, connector 40 and/or BMS 30. The malfunction of any one of the cells 10 or the battery system 1 may cause a loss of one voltage signal or several voltage signals, which would lead to a disconnection of the battery system 1 and a loss of propulsion energy of the electric motor.

[0038] Accordingly, the control unit monitors S1 a state of health of each of the plurality of cells 10, wherein the state of health may be a cell capacity, a cell resistance and/or a cell self-discharge rate. As soon as the control unit detects S2 at least one malfunctioning cell, a cell balancing unit is turned off S3 and the state of health of each cells 10 just prior to occurring the malfunction is maintained.

[0039] The control unit analyses S4 the collected data, in particular the state of health (SoH) of the malfunctioning cell. If the malfunctioning cell 10 has a worst SoH in the battery system 1, the control unit limits S51 or decreases a discharge power and slowly reduces a minimum state of charge (SoC) of the battery system 1 over a time period. However, if the malfunction cell 10 has a best SoH in the battery system 1, the control unit limits S52 or decreases a charge power and slowly reduces a minimum SoC of the battery system 1 over a time period.

[0040] Further, the control unit analyses S6 a trend of the SoH of each cells 10 by evaluating the SoH per a predefined time unit. If the malfunctioning cell 10 has a worst trend of state of health in the battery system 1, the control unit limits S71 charge and/or discharge power and reduces a charge or discharge maximum time until the malfunction is repaired. In other case, a normal operation is allowed S72, since the charge and/or discharge power may be limited by other cells 10 with a worse trend of the SoH.

[0041] Accordingly, the battery system 1 may operate without interruption even a malfunction of any one of the cells 10, thus a robust and reliable power supply may be ensured.

[0042] It has to be noted that embodiments of the disclosure are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the device type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

[0043] While the disclosure has been illustrated and described in detail in the drawings and description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The disclosure is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed disclosure, from a study of the drawings, the disclosure, and the dependent claims.

[0044] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.