If your battery has a broken bar or the settings for that size/voltage of battery are set wrong, this message will appear. It has happened to me before. I didn't know what was happening. After messing with the battery I would find loose battery bars. Resoldered it and and started charging. Also I've mistakenly put the wrong profile on for the wrong battery. The charger was looking for a 3 cell lipo and not a 7.2v side x side pack.