Chosen Solution

After replacing the battery, my iPhone is restarting after a few minutes in use, and the battery doesn’t charge past 10% of capacity. I’ve restored the iPhone and tested with other (good) batteries but the problem persists. The crash code is “Panic CPU x caller”, and the reason “Problem connecting CPU and peripherals”. I can paste the crash logs here if needed. Anyone has faced this problem before?

Your phone is restarting because it cannot determine your battery information. I would check the battery connector on the logic board. If it is not the connector it will be another component on the charging circuit that has failed. The only other thing you could check and maybe replace would be the dock connector but this would be highly unlikely on the 6s.