I dont know that this will help but:

I had a similar problem , while balance charging, the balance conector on the charger had become a little loose.
A 'batt. voltage error' message was displayed, so , I tried again , putting finger pressure on the charger side balance tap. As soon as I released finger pressure , I go the error.

A small strip of thin lexan wedged between the balance tap and the balance tap case fixed it.