Battery Backup Guide

I <3 Jonathan Davis asked:


I am going to buy a backup battery for my camera on ebay, I have found one that is made for my model of camera and has all the same specifications apart from the capacity.

The capacity on my current battery is 740mAH and the capacity on the new one is 680mAH.

What does it mean by capacity and does it matter that the new one will have a slightly lower capacity?

Thanks

Jugi asked:


I’m looking to get a new digital camera. I’ve been looking at a lot of the very small ones, and noticing that they all seem to come with their own rechargeable battery. My current camera uses AA batteries, and when I use lithium batteries, they seem to last forever. (Regular batteries are eaten up quickly.) I do tend to take lots of pictures - basically anything that moves (and I guess everything that doesn’t too). Would I be sacrificing on battery life by choosing a model that comes with its own rechargeable battery? I’d hate to be on vacation somewhere and the thing just dies in the middle of the day. Also, are backup batteries expensive?
My main concern is how many pictures I can get out of a single charge.