Can I put an iPhone 8 Plus battery in iPhone 8?

Hi Ivan,

The short answer is no, you'll never get an 8 plus battery to fit in an iPhone 8. I'm not sure where you got your information, but the two models most definitely do not share the same battery dimensions.

The thing about Lithium Ion batteries is that their mAh capacity is determined strictly by the physical dimensions of the battery. Unlike other technologies, there aren't any improvements you an make to them like you can with Ni-Cd batteries where you can fit more storage capacity into the same physical space.

So the iPhone 8 is rated at 1821 mAh and the 8 plus comes in at 2691 mAh. Since those capacities are directly tied to the physical size, that tells you right there that the 8 plus battery is almost half again as big as the 8 battery.

That's backed up by a site called batteries4pro.com that lists the physical dimensions of the batteries.

iPhone 8: 92.7mm x 38.5mm x 3.5mm = 12,491 mm^3

iPhone 8 Plus: 108.8mm x 49.3mm x 3.28mm = 17,593 mm^3

As a general rule of thumb, you will almost always be correct if you assume that any given part for one phone will not fit in another phone. There are a few exceptions, but far and away most of the time that'll be correct.