With a TM, I would guess that you are using 2 cell packs. The Apache 1215 has served me well over the past 14 months. Ay $30 they are a terrific charger and a great bargain. If you plan to go to very large packs, or a number of different sized packs, then I would suggest you look at the Astro 109 for $130. Lightflight RC handles both and Dave is a great vendor.
http://www.lightflightrc.com/