Introduction - Quite a few years ago we were all happy to recharge our power packs from the car battery, although some found that this was not a good idea after a days flying when the car refused to start - flat battery. As time went by our power packs got bigger and bigger and more powerful to go with our larger electric aircraft.  This is becoming a problem!  We then turned to leisure batteries which are by no means cheap, a 75 amp battery could easily set you back by £120 and upwards.  As my aero fleet increased and a sizeable number were electric requiring 6 cell packs at 5000 mah I was now going down the "adding more expense" route to my pastime.