Battery issues after work don on the screen
Hi, I bought an iphone 6s of a friend with the intention of putting a new battery in. What happened was that my friend did a screen replacement, unconnected the battery first and successfully put a new screen on. However after he did this the battery started draining stupidly fast as in 3% in 2mins just with the screen on and not using the phone, faster if the phone is being used. When it is on charge the battery still goes down just not as fast, the only way to charge it is to turn the phone off while on charge, if the battery runs to nothing then it will not recharge!? Its had 2 new batteries just to rule out the battery itself and still have the same issue, i fear he may have damaged the board or something in some way. Any advice would be greatly appreciated.