[skeleton]

Just a personal experience: I had bought several ~$20AU iPhone 4S batteries from eBay from different sellers, and while they started off okay their capacity dramatically decreased after a few weeks.

Also I'm unsure on how a device determines battery charge, but I forever had issues with the phone turning off while reporting the battery had ~30% left.

Maybe I didn't treat the batteries correctly, but I can't recall as this was several years ago.

[vortico]

I've had great success ordering OEM Samsung batteries for Galaxy S3 and S5, $3 and $7 respectively, that are still working after several years.