Overvoltage or undervoltage alarm .
Possible Cause：The battery string voltage is not within the range set on the controller.
1. Check that SCBs are connected securely. If a connector is rusted or oxidized, rub the corrosion layer.
2. If a connector is loose, secure it.
3. Measure each battery voltage when storage batteries are discharging. If a battery voltage is lower than the average voltage by 90% or lower than other battery voltages by more than 0.2 V, replace the storage battery.
Measure each battery voltage when storage batteries are being charged. If a battery voltage is less than or equal to 11.0 V or greater than or equal to 15 V, discharge the storage battery and then charge it in equalized charging mode. If the voltage still deflects from the threshold, replace the storage battery.