I have the same engine. you can use a 1100 to 1600 ma 4 cell nicad or NeMih pack depending on how much you fly on a given day. I use a switch with the charge jack built in. Just hook the battery to the switch and charge as usual. you connect the output side of the switch to the electronic module. Make sure you do not turn the engine over with the power on with out the plug wire connected to the spark plug, and the plug 's shell connected to ground on the engine. If not you can damage the module.
Gary