I replace all my receiver packs with 4.8 volt 2200 Mah packs and add voltwatch monitors to every plane . When i was flying my Superstar Trainer , i flew a whole gallon of fuel one day on that pack , and still had juice to spare . I recommend the voltwatch monitors as cheap insurance , and takes the guesswork out of pack capacity . You can use the voltmeter too , but why mess around with that when you can check your condition at a glance .