Karry (Kairui) new energy electric vehicle does not power on at irregular intervals.

Brand: karry

Model: SQR5025

Fault phenomenon: It fails to power on from time to time. It powers on with the key. It powers on occasionally, but fails to power on after a few attempts.

The following fault code is displayed when the fault detector is connected:

There were 3 alarm faults. Since the vehicle had no power and the battery current sampling was abnormal, it was preliminarily judged that the battery was working abnormally.

The battery and battery management system (BMS) are both from Anhui Tianxin Energy Technology Co., Ltd. The BMS uses an efficient host computer for monitoring. The host computer independently checked the working status of the battery and found no other abnormal information except the insulation alarm. It is worth noting that as long as this battery has an abnormal working state, it will be notified in the form of an insulation alarm.

After the battery initially reported low motor power, a BMS replacement was performed. Although the new BMS was the same vehicle model and battery as the original, an interlock issue occurred due to a different software version. To resolve the issue, the original BMS was reinstalled with the interlock function disabled, and the test run was normal. It was ultimately confirmed that the issue was caused by the interlock.

Battery pack appearance

In order to accurately locate the problem, the method of short-circuiting each socket one by one was adopted. Finally, the motor socket was located to have poor contact. However, since this specific type of socket was not available, a temporary solution was decided to be adopted - directly short-circuiting the internal socket. With this method, the fault was successfully eliminated during the test run.

High voltage interlock schematic

Although the problem was fixed, the damaged outlet needed to be replaced to ensure long-term safe operation.

New energy electric vehicle framework and driving process