Get a Grip.

[Stradawhovious]

hehe careful with putting it on and off though. Myself with a wriststrap (and liking the grip so much) I never had a need to take it off again - however you can get them stuck on the camera if you tighten the grip on too tightly (and yes this has happened to my 400D)

Good safety tip Egon!

With mine, I will have plenty of need to take it of again. The grip dosn't contain both batteries, only one. The other battery still lives in the body itslf. So if I want to use both, and I do, I will need to make sure I don't get the grip stuck.

 

[Overread36]

Hmm interesting design - with my grip (official canon batterygrip) both batteries live in the grip itself. With the 400D (which hasn't got chipped batteries) I keep 2 batteries in the grip and 2 spare outside the grip - if I on'ly had 2 I'd keep one in and one out (that way ensuring that I always have a spare battery in the pocket so when needed I can just change over and put the other on charge - rather than having all the eggs in the grip and running out of power with no warning). The 7D is a little better with power management so both batteries tend to live inside it, though I'll probably add one or two more (esp if I get into video more since that eats power far faster than stills.