I have had the same (or similar) problem with two different extended batteries: The batteries seemed to not take a charge. When plugged into the charger, the phone would run, and a flash would appear in the battery icon—but the charge percentage didn't rise above 0%. If I changed to another battery, it would work normally. Well today I found the solution (here) Solution: (1) Turn the phone off. (2) Remove the battery. (3) Wait 10 seconds. (4) Plug in the charger. (5) Insert the battery. (6) Turn on the phone. I now have two working batteries :-) I think that the circuit in the battery that protects it from overcharging and undercharging needs a reset.