The ibec is set to 6.1 volts. It is a 5 cell. The reason I used the NiMh batteries is because I had never heard or read not to. I did however talk with Tech-Aero about this and was told that it may be part of the problem. I have also been using NiMh batteries in a plane with the older larger ignition module and RCexl Opti switch for the last year and a half with no problem. I have A123 batteries and will try that. Thanks Truckracer