If you have any sort of suitable output, you can forgo the charger and battery.

I hooked my Hobbico starter to a pair of 7.4 volt RC car batteries, and it produces far more power this way, while lasting me through several weekends of starts for each charge. This was cheaper than using the commercial battery packs and far better.

The starters can work with 12v through 16v w/o problems and some people run them even higher.