

How to check battery for spiciness if it's not visibly spicy?
As example got some powerbanks that don't have any noticable way to open them up without completely destroying them but I feel like they don't have theirs full capacity either. Xiaomi is like a hard plastic, actually good quality despite what you all think about their products. The other one is acme where outer shell is metal so I doubt bulges would appear.
I guess some way to measure actually mAh would be a way in this case but how exactly to do that?
Easy way would be to measure voltage but it will be 5V on the USB output.
iPhones has battery health in it's settings (if it's original battery or it's been tricked into believing it's original after replacing). So does android apps are reliable on this or it's just malware?