I like the AC-6 from Hobbypartz.com
It has AC/DC operation so you can use it anywhere. It has an adjustable charge rate so you can charge faster and of course a built in balancer. It does have a 50 watt max rate, which you will only see if charging large packs for 1/8th scale use, and even then it will still charge perfect, just not as fast. But for normal 2s or 3s packs it will charge about as fast as you want.