iPhone keeps reseting and goes to 1% battery

Hi Noa,

Starting with the iPhone XS and XR, Apple started pairing batteries with the logic board. The result of this is that when you change the battery you lose the battery health information and you get the non-genuine part warning. There are two ways around this problem; first you can have Apple replace the battery for you and everything will be fine.

However, if you're not Apple and still want to replace the battery, you have to remove the BMS or Battery Management System from the old battery and transfer it to a new battery cell. The BMS is a small circuit attached to the battery that provides storage for the battery health and cycle count information and communicates with the motherboard. Nowadays you can buy replacement batteries that come without the BMS for the specific purpose of reusing the old one.

Once you've cut the BMS off the old battery and soldered or spot welded it onto a replacement cell, you're still left with the original health and cycle counts. On the XR you can reprogram that information with a device programmer like the JC V1S or the Qian Li iCopy.

It sounds to me like all that was done correctly when you had the battery replaced (assuming you didn't have Apple do the work), but now it's giving you problems. It sounds like you may have a problem with the BMS itself; that would explain the error messages you're getting. Unfortunately, if the BMS is failing then it will need to be replaced. If you don't have Apple do the replacement, you'll lose battery health and get the warning; there just isn't any other workaround for it.

It's possible the connection to the BMS is flaky so it would be worthwhile to go back to the shop that did the replacement originally and see if they'll check their work; hopefully they'll stand behind their repair.