iPhone boot loop after battery replacement?!
while we replace the battery for iPhone 6, we plug the charger into phone without battery.
and after while we replace the battery and the phone stuck in reboot loop.
There are a couple of things that we could try. We want to make sure that the iPhone is being recognized in iTunes.
If the iPhone is recognized in iTunes, send me a screenshot of the device page in iTunes.
If the iPhone is not recognized, try plugging the device into the wall charger again and leave it charging for 6 hours. Be sure to use a known, working, MFI charger.
I recommend is trying a DFU Restore, and the instructions on how to do so can be found here: *click*.
DFU stands for Device Firmware Update, and because it reloads the software and the firmware, it’s an even deeper restore mode than the recovery mode Apple describes on their website. Be warned though that if you haven't upgraded your OS to the latest compatible version this will upgrade your device and it is not reversible once completed.
Hope this is helpful, and best of luck!