So I have a pair of Canon BP-511 batteries, a pair of Digipowers (Best Buy Brand), and finally a pair of Sterlingtek's. I decided to put these to the test today, to see just how many shots I could get out of each pair. My 40D takes about 108 shots in a row, at 6.5fps. Yes, the buffer is 75, but by the time you're at 75 shots, already part of the buffer has been cleared as the camera has written some images to the card. The process is simple. I have 2 of like batteries in my grip, fully charged, and hold the shutter down until the buffer fills up. I await the buffer to clear, and fire away again. When a card fills up, I just swap, and my wife formats the card on our laptop so that no time is wasted. Here are the results. Canon BP-511's (2 batteries) Test 1: 3022 shots Test 2: 3001 shots Test 3: 3480 shots Test 4: 3334 shots Test 5: 2599 shots Test 6: 3252 shots Test 7: 3250 shots Test 8: 3163 shots Test 9: 2939 shots Test 10: 2833 shots Total after ten charges: 30,873 shots in 10 charges Digipowers Test 1: 2554 shots Test 2: 2488 shots Test 3: 2541 shots Test 4: 2501 shots Test 5: 2575 shots Test 6: 2302 shots Test 7: 2529 shots Test 8: 2285 shots Test 9: 2322 shots Test 10: 2110 shots Total after ten charges: 24,207 shots in 10 charges Sterlingteks Test 1: 3950 shots Test 2: 3844 shots Test 3: 4005 shots Test 4: 2033 shots - something must've gone wrong here Test 5: 3790 shots Test 6: 4010 shots Test 7: 4003 shots Test 8: 4025 shots Test 9: 3888 shots Test 10: 3920 shots Total after ten charges: 37,468 shots in 10 charges My conclusion. The Sterlingteks certainly outperform the Canons, and most definitely the Digipowers. The Sterlingteks did show in test 4 some weirdness, as noted...which makes me wonder if their inexpensive price tag is showing through. Nonetheless, the Sterlingtek batteries provided 23% more shots per 10 charges than the Canons did. Tomorrow I'll use a friend's Nikon D300 to perform the same tests. Has anyone else done similar tests on a Nikon?