I recently posted a review on the aftermarket Battery + Grip for the 550D / T2i. Someone asked me how I would be doing my test comparing the battery life. Since I can't shoot continuous video until the battery dies, I thought doing a Timelapse test could possibly show if the photo count would be significantly more or less. For this test i'll be using the Intervalometer (timer remote) purchased for just $23.00 dollars + free shipping. One important thing to remember when buying an Intervalometer is the maximum number of pictures it can take. Some are limited, not sure why, but the one here had a 00 mode for unlimited shooting.
I won't be using the grip because that will take forever for the batteries to die. I'll just be comparing one battery against the other trying to figure out how many photos it can take before the camera batteries run out of juice. I'll let you know how the test goes when I can find a full day to run the timelapse (and something interesting to shoot too). You can purchase this Timer remote for as little as $23.00 + Free Shipping.