I've got an Apple Smart Battery Case[1] for my iPhone 11, which is a similar idea, and the extra battery life can definitely be handy. Doing it with a swappable

I've got an Apple Smart Battery Case[1] for my iPhone 11, which is a similar idea, and the extra battery life can definitely be handy. Doing it with a swappable battery is a neat twist though - I haven't seen that done before. [1] I picked up a cheap used one - they're rather expensive at full price (£129). It can charge my iPhone from 10% to 60% though, so it's current capacity roughly matches its design capacity.