you should use 1.5 alkaline batteries in both. Rechargable batteries are 1.2 volts so you do loose a few volts over a couple of batteries. the transmitter should still light up though. i would suggest putting some alkaline in the car and transmitter and see what happens. the redacats are kinda known for bad radio systems but they do make good on it as long as it hasnt been over 30 days. I would suggest buying a new radio system though, like futaba or jr.