Chosen Solution
Hello, I have a customer here, he has a device with no damage whatsoever, all i did was change the battery and the Display, now the battery is going haywire, i sent him off with a completely new device, no scratches or dents. new Display and battery, i thought, okay i made some profit, cool and good. after he got back to his home he called and told me: “THE BATTERY IS DOING SOME WEIRD $@$*!” i was like: WHAT how?? i replaced it! he said that he’s gonna come again and give my the device. i took a look, replaced the battery with a different one, same problem! i put the old one in ( which i wrecked ) same problem, how can this be, that 2 completely new batteries and the old one have the same problem, the board is completely fine, heres the problem: Turn on, Battery at 1%, plug in: Battery Jumps to 31%, plug out, Jumps to 44%, plug in: suddenly 100%, i did a complete reset and stuff with software, nothing helped. every now and then the battery hits 0% and it shuts off, funny part: without warning also while charging really frustrating… Another funny thing laughs while crying : it works completely fine in DFU mode or Recovery Mode, like no crashes or anything. i asked the company that sent me one of the iPhone 5S Batteries to send me a new one, they agreed.
You may have accidentally dislodged some components near the battery connector. They are very tiny and one of them is on the line that communicates the battery charge state to the CPU. It’s a very common failure on the iPhone 5S and your symptoms match up very well to this issue. Whip out your magnifying glass and take a look at the battery connector area. Look for any missing parts, specifically the one highlighted in yellow here:
