The 50D batteries I have say they are 2000mAh. However, after reading a vast number of resources, I can tell you that the stated mAhs are almost always grossly inflated on 3rd party batteries. However, I purchased an Opteka battery grip for my XTi that came with two batteries, and they worked fairly well. However, it is very common for 3rd party batteries to deteriorate in performance over time (much quicker than the standard OEM batteries, I believe).


All I can tell you is that both sets of Opteka batteries I've owned (for the XTi and 50D) have surpassed my expectations. It's important, though, to use them once they are charged. I think they will probably lose some of their luster if left idle for too long (although I haven't tested this). What I do know is that a comparable 3rd party battery is less than half of the OEM price...and if the 3rd party battery has half the life or more of an OEM battery, you've still come out even or ahead.