im trying to build a simple glow driverthat i can leave attached to the engine and turn it on and off at the flick of a switch. ok all good there. but the problem im having is that the only battery i can get to light the plug is the nicad that came with a proper glow driver. i have tried ordinary batteries but they dont work, ive tried single AA, C, 2 AA but none work. just the nicad c cell. Any reasons for this??? im stumped.