That's a good idea too. However, if you only fly one or two planes then field charging would cost about as much as new higher, capacity battery packs. If you have more planes then obviously it would cost a bit to buy all new packs. Then a field charger would be handy and economical. If you're like me, you couldn't be bothered with having to hook up my batteries to a field charger, field battery (which also needs some maintenance) or car battery, and have to time them etc. etc. AND cycle them periodically to get the most from them. It sounds like you just want more flying time. Higher capacity packs are the easiest way to go.