XT battery life?

I have started shooting pics for my son's high school wrestling team. Yesterday I shot over 1000 images and went though four batteries!!

I have a Rebel XT with a battery grip. When the camera is in servo focus mode, I am only getting about 500 shots out of two batteries. Is this normal? I would assume the camera would use more juice in servo focus, but this seems a little extreme. The batteries are aftermarket from Sterlingtek, I have have the camera set to not preview shots on the LCD and I am not reviewing my shots often. No flash used. Do I need to buy some new batteries?

Shaun

Were they freshly charged? Personally I always feel the genuine Canon batteries work better than the cheap knock-offs.

I can't say I've ever run out of power with my XT. Mind, the most photos I've shot is 200 in a day and with single AF.

Are you depressing the shutter button to keep the lens focussing? And which lens are you using? Whenever the shutter button's partly depressed, in addition to the lens being focussing, the IS will be working away if you've got that. If you spend the entire match leaning on the shutter button so you're ready for the shot, you will go through batteries pretty fast, especially with IS on.

Yes, I charged them all the night before. I did not pay much for the batteries, but would hope they would last for awhile? I have rotated them around for about 6000 shots in the last 8 months.

Shaun