For battery suggestions, the venerable old NiCd is the most durable thing you can get. LiFe is making serious inroads for receiver packs because it is lighter, but for a trainer there's really no concern about that. Grab one of the cheap multi chemistry chargers from HobbyKing for about $30. It will be able to fast charge any battery type you ever use. Just make sure you get one that can cycle because cycle testing is the way we verify our packs to make sure they are still good from time to time. For NiCd brands, you want Sanyo cells with welded construction. Most of the big brands have that, but I get mine from www.hangtimes.com. Go with a 5 cell pack to give your servos a little more power and prevent receiver brownouts in case you go with Spektrum radios.