My camera manual for EOS 50D says I can use either BP-511A, BP-511, BP-512 or BP-514. The camera came with a single BP-511A. Does anyone know what A stand for? How is BP-511A different from BP-511?
Also, I found an online shop that sells BP-511 replacements, and they state that it replaces BP-511, BP-512, BP-522 and BP-535. How does BP-522 and BP-535 come into the picture? These two are not mentioned in my manual.
Should I assume that pretty much any Canon EOS battery with the same size, voltage and shape is good with my camera? Are the Canon EOS battery packs compatible across all EOS models? I know that battery grips are different, but I don't know about the battery packs.
Update:
Here's a battery compatibility table I compiled based on the responses I got here and information from various web sources featuring the mid-range and advanced Canon EOS models.
Battery Delivered Optional
D30 BP-511 BP-511A
D60 BP-511 BP-511A
10D BP-511/BP-512 BP-511A
20D BP-511A BP-511, BP-512, BP-514AC
30D BP-511A BP-511, BP-512, BP-514
40D BP-511A BP-511, BP-512, BP-514
50D BP-511A BP-511, BP-512, BP-514
5D BP-511A BP-511, BP-512, BP-514
60D LP-E6 n/a
7D LP-E6 n/a
5D mk2 LP-E6 n/a
5D mk3 LP-E6 n/a
Note that there is no optional battery pack for the LP-E6 at the moment. The BP-514AC is said to have an optional DC coupler. I'm not sure what that means. But I imagine you can attach something to it that will allow you to plug it directly into the electrical outlet to charge it. It is sort of a battery and a charger all in one. I think...
Here are the battery capacity specs for the above mentioned battery packs. These numbers apply to the original Canon battery packs. Replacements can have higher capacity.
BP-511 1100 mAh 7.4 V
BP-511A 1390 mAh 7.4 V
BP-512 1100 mAh 7.4 V
BP-522 2200 mAh 7.4 V
BP-535 3500 mAh 7.4 V
So if you can use a BP-511 and you're going for the original (OEM) battery pack, go for the BP-511A which will give you the best battery life.
Give me some feedback if you find this helpful or if you see any errors.