The purpose of the battery self-discharge performance test is to verify the charge retention capability and charge recovery capability of EV battery systems under long-term standing conditions. At the same time, the voltage difference of the minimum monitoring units in the battery self-discharge performance test can be used as a basis for whether there is a hidden danger of internal short circuit inside the battery system.

During the standing process, disconnect the high and low voltage connections of the battery system, turn off the cooling system, and disconnect any other necessary connections. The SOC of the battery system can be determined on a case-by-case basis.

The temperature of the test is 45℃, and the temperature environment is provided by the temperature chamber for battery systems; the test period is 168h and 720h. The specific test procedure is as follows.

1) Discharge the battery system to the specified discharge cut-off conditions in a specific discharge procedure at ambient temperature.

2) Allow to stand for not less than 30 minutes.

3) Charge the battery system to full charge with a specific charging procedure.

4) Allow to stand for not less than 30 minutes.

5) Adjust the SOC of the battery system to the target value.

6) Place the battery system in 45℃ environment for 168h or 720h.

7) Allow to stand for not less than 8h at ambient temperature.

8) Discharge the battery system to the specified discharge cut-off conditions in a specific discharge procedure at ambient temperature.

9) Allow to stand for not less than 30 minutes.

10) Charge the battery system to full charge with a specific charging procedure.

11) Allow to stand for not less than 30 minutes.

12) Discharge the battery system to the specified discharge cut-off conditions in a specific discharge procedure at ambient temperature.

Record the test results in Table 1-1.

Table 1-1 Battery self-discharge performance test record sheet

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