I run 2x 2s lipos. They always charge and balance correctly, to within .01-.02V (or so my charger says)
My runs are always fine for 30-40mins, but then the car will start chugging. I plug the lva in and in only one of the batts the cells are bout .25V apart (usually 3.3 - 3.65). So I always call it day, then re-balance them properly.
Any idea what causes this? Is it the car or the batt?