I replaced one battery in my transmitter battery pack. For as long as I’ve had it, the transmitter was only good for just barely 1 1/2 hrs of flying time per charge. I finally tested it and found that one cell was completely shorted out, 0 volts. I think that it’s always been like this but I never looked into it. The new battery is a Radio Shack 700mah AA cell. The other batteries are 600mah cells. I hope it works alright.