As it stands the iPhone 6 has a battery size of 1,810mAh. However thanks to the folks at Nowhereelse.fr (via MacRumors), they appear to have gotten their hands on what looks like a battery belonging to an unlaunched iPhone. The battery size in question is 1,715mAh which makes it smaller than the iPhone 6.
This has led to speculation that it could be for the rumored 4-inch iPhone 6c, although the last we heard about that phone, apparently Apple had decided to scrap their plans for it. So perhaps this battery could indeed be for the smaller device, but we may never find out if the rumors about it being scrapped are true.
Alternatively if this battery were to be used in Apple’s next-gen iPhones, safe to say that many users will probably not be too happy about it. It would also mean that Apple would have somehow increased the power efficiency on their devices in order to stuff a smaller battery but yet somehow offer up the same battery life as its predecessor.
Granted software optimization does help with battery life, from a marketing standpoint it does look better if the numbers are bigger. In any case we suppose only a teardown of the next-gen iPhones will tell us what kind of battery sizes we are looking at, so until then take it with a grain of salt.