Driffill said:
Until recently, I'd agree with the size to capacity ratio, meaning a 2700mah battery must be bigger than a 2200mah . . .
But, the lipo battery itself (lithium batteries in general) has been breaking thru the limits of conventional batteries. The 2200mah DJI phantom battery is at least 1 year old in its design, and 1 year is enough for manufactures to improve their own products. . .
That said, empirical data of claimed capacity is the best thing to rely on. In my kit I have a 12v lithium-ion battery with a claimed capacity of 6800mah, I haven't tested it to be sure of it true capacity, but in terms of size, it would have to be close on the same volume as the dji 2200mah li-po battery. I think to think I'm up with things in terms of electronics, but these lithium batteries are starting to make me wonder about size/weight/capacity limits
Essentially, you're saying there's a difference in chemistry. That may indeed be the case, and over time battery chemistries WILL and DO get better, guaranteed. But it's a pretty slow process to go from research to validation to manufacturing. At the same time, it's so easy (and really, an EXTREMELY common tactic) to exaggerate the rating on the label of a battery using non-standard test methods (or no testing at all). My Chinese 1050mah GoPro batteries all say "1300mah" on them and they're nowhere near that. Some sites selling them even have an extra field for "true capacity" because of the prevalence of this practice. Unless there's clear and evident proof that an rc battery maker has made some huge improvements in battery efficiency, I'm going with physics.
I think a lipo will always have a lower discharge capacity than a li-ion of the same volume; it's a consequence of the solid electrolyte. They names are similar but the chemistries are very different.
FWIW, I've found the DJI 2200s to be fantastic. They're true-rated and constructed extremely well, appear to outperform their C rating, and they're quite light for their rating. I've run into a few duds on the cheap from HK and will be sticking to the DJI batteries from now on.