I agree that having a standard nomenclature for size and voltage is a great thing, and something it seems that is being ignored across the board for consumer electronics. As GeneC said, I don't understand why two Canon cameras would use two different batteries, both the same size but with slightly different "keys" so they can't be interchanged. Actually, I do understand why - it's a great opportunity for manufacturers to make extra money.

I can say, however, that I am happy that some companies diverge from standard sizing on boats. I can fit almost 800AH into a pretty small spot on our boat because of the availability of the slimline Mastervolts. If I was to use golf cart batteries, I'd be at about 560AH and would have to steal space from an additional storage area (in addition to having to deal with the issues around charging and discharging batteries with different locations).

Also, with regards to "standard sizing" - when I was looking at what I could cram into our battery location I found that most 4D's and 8D's differed in size AND capacity. The designation seemed more like a guideline than a standard.