HV Batteries SOC Suddenly Increases or Decreases

Created by John Jackson, Modified on Thu, 2 Oct at 2:40 PM by John Jackson


When the SOC of the HV Batteries jumps suddenly to a High Value (eg 100%) during Charging, or suddenly drops to a Low Value (eg <10%) it is likely that one or more of the Battery Modules in the HV Rack are much lower SOC than the rest. Therefore these Low Battery Modules will need to be connected to the BMU on their own and charge them up to the same SOC / Voltage of the other Battery Modules. Then reconnect them all and Charge them all to 100% together.


NOTE - The minimum Number of Batteries that can be charged together in a stack are 4. If using the instructions below you identify that you have less than 4 Batteries which are low SOC then please contact Support for further assistance


Rectifying a Battery Unbalance
If a battery unbalance has been confirmed please follow the below instructions to rectify the issue:
  1. Disconnect each battery.
  2. Adjust the Number of Batteries in the BMU to match the number that are being charged. (Min = 4)
  3. Reconnect just the Low Batteries only and charge up so SOC matches the rest of the Modules.
  4. Reconnect all of the Batteries in the HV Rack and reset number of Batteries back to the total.
  5. Grid charge all of the HV Batteries to 100% (this allows a recalibration of the BMS)

Please review attached video to enter the BMU System info and enter Volt/Temp section to read the Max and Min Cell Voltages. The box to the right of the Min Voltage Value will tell you the Battery Module Number and Cell number of the lowest Cell Voltage so you can identify which of the Battery Modules are the lowest. If more than one Cell in the HV Rack is equal to the Min Cell Voltage then the Module and Cell Number will scroll through each affected Low Cell. This will allow Low Voltage Battery Modules to be identified so they can then be charged up to match the Max Cell Voltage value before connecting them all back in series in the HV Rack.



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