Battery cases safe for iPhones?
The iPhone 7's battery barely lasts a whole day so I am looking for a battery case to extend the juice just a little. The ones on Amazon look really nice and promise up to 4000mah.
Are non-Apple battery cases safe (i.e. not the case sold by Apple)? What is the difference between non-Apple and the Apple battery case? And will they potentially damage the phone?
Any technical or anecdotal answer is appreciated.
Thanks
iPhone 7, iOS 10.3.1