If like me with the arrival of DSLR cameras you've gone nuts and snapped pretty much anything that has got in your way then you'll know about running out of power at a crucial moment and losing the best shot of the day because of a flat battery. Simple answer, buy another. The Canon NB-2LH fits my EOS-350D perfectly and is also designed to be fitted into the BG-E3 Battery Grip for the EOS 350/400D. My advice, don't risk it, buy another battery.
I've given this item four stars rather than five because of the price - some compatibles are cheaper but may not perform as well.