I've been using the Energizer rechargeables in my AT Pro for over 3 years now with great results. Once charged, they seem to last as long as regular alkaline batteries. Plus you're not spending money every time you need to change the batteries out. I recommend them.
I bought a set of RNB batteries for my AT Pro. "16 hours and 40 minutes got me down to 2 bars. We can only guess how many more hours the battery pack would work until it completely goes dead.Maybe another 10 or 15 hours? I am happy with mine.The real bonus for me will be hunting in the cold weather."
Maha PowerEx 4 AA 2700 mAh NiMH Rechargeable Batteries with case, about 12$ for a pack on the bay. I use them and they work just fine on my AT Pro..