We have had reports of unexplained HVD faults on Morningstar controllers connected with lithium battery banks that contain a BMS. This appears to be caused by the BMS disconnecting and reconnecting very quickly which results in voltage transients (spikes) on the controller battery terminals and in turn exceeding the HVD threshold.
This is typically caused by the controller’s absorption charging voltage exceeding the max allowable charging voltage of the BMS, usually due to improperly configured charge profile settings and/or excessive temperature compensation of the target charging voltage in cold temperatures.
Troubleshooting solutions you may consider:
Confirm the controller Absorption voltage is programmed within the specification of your battery manufacturers recommendation
Set a max charging voltage limit in the custom settings
Add the Voltage Sense connection (if not already in use) between the controller and the battery bank
Adjust HVD threshold on the controller to a higher value
Disable HVD - HVD provides protection for the battery and controller so this should only be done temporarily for troubleshooting purposes.
If the above steps do not resolve the issue, you can confirm the BMS is causing this issue by temporarily swapping out the lithium battery for a lead acid battery but leaving your controller programmed for lithium(this will not hurt the lead acid battery or the controller). If the HVD fault is not present while using the lead acid battery then your lithium battery BMS is the root cause of the HVD fault.
You should also consider discussing the BMS with your battery manufacturer to see if they have had reports of BMS failures. Your battery manufacturer may be able to aid with acquiring data from the BMS to determine why the BMS is disconnecting and reconnecting. They should also be able to provide recommendations on how to avoid these types of issues going forward.