Chosen Solution
I just replaced someone’s iPhone’s battery. Everything seemed to go smoothly. The phone booted up, took a charge, and loses battery at a consistent rate. However if I let the phone drain fully and I try to recharge it, the phone simply won’t turn on. This problem has happened both on this 6s as well as my own 6. I’ve gone through 5 batteries overall with the exact same issue.
Always use original parts in replacements. Every product has a specific design and working profile set by its company according to devices. When you plugged other brand battery first time it may be short your motherboard IC. As describe above by Shawn, check your mobile board. You should also check your charger. Might be the charger is not working well, and you are changing your batteries.
Was it a good quality battery? Never have seen this, maybe you have recieved poor quality battery. Try from differrent supplier.
With the Iphone 6s it has a known issue with the wifi IC shorting out internally. It will need a new Wifi IC and have Nand removed and wifi unbinded. Motherboard issue 100%
