Hi All - The recent thread about carrying spare batteries prompts me to ask some more general questions. I've done a quick search of CiC but I don't think it's been addressed before. When I bought my Canon 40D nearly two years ago, it came with a Canon Brand BP-511A battery pack (aka E160814). This is a Lithium Ion 7.4V 1390 mAh system. I bought a second Canon Brand battery, but now no longer know which is which. For general purpose work I was getting about 200-300 shots per battery before having to recharge. Now, one of the batteries is giving only about 50-60 shots per charge.
First question: is this normal battery behaviour? I assume that it is.
Second question: is there anyway to rejuvenate batteries that are worked out?
Third question: is there an easy method of testing the state of a battery other than by recharging and re-fitting in the camera? I'm thinking multimeter here.
Fourth question: what are opinions on 3rd party batteries? Duracell and Energiser both market BP-511A replacements and Amazon and other reviews give high ratings.
Fifth question: are there any good professional reviews of battery ratings?
Sixth question: why oh why is there such a huge price difference between official Canon batteries (I've seen £90 quoted) and other brands (the Duracell version is about £15)?
While I'm obviously interested in the BP-511A battery, I reckon the questions can be applied generally.
Thanks for any help.
Cheers
David