[Droid RAZR M Q&A, Help & Troubleshooting] CallMeAria:
Trying to fix a family members xt907 so here's the situation which has been nothing but headaches for me:

1. The Phone is only 7 months old and the bootloader is unlocked so warranty exchange is out of the question. She let the battery run down until the phone died. Then without charging the phone she turned it back on and it died again. From that point she couldn't get it to charge or turn back on while plugged in. At this point she brought it to me.

2. I got the phone and did a soft reset which finally got the charging screen to come up (showed the actual charging icon and the fill meter would flash up and then back down periodically). Problem is it never went past 0% after charging all night. I went ahead and tried to power it up thinking maybe it was just a glitch with the charging screen. Phone wouldnt boot. Just stuck at the Motorola logo. Another soft reset and the phone finally boots but now the battery icon showed a '?' and status showed '5% - Unknown'.

3. Performed a factory reset. No change. So I used RSD to flash the stock 4.1.2 firmware/kernel/modem, etc... What I found strange here is that despite the low battery Fastboot AP showed battery as OK, not low and let me flash (bootloader is unlocked, not sure if that affects low battery flashing or if that safeguard just wasnt built into the M).

4. So phone boots back up and shows 7% battery. Plugging in the charger at first notice has no affect. Battery stats shows '7% - Not Charging'. So I unplug the charger and the low battery warning pops up. Plug it back in and phone still doesnt register as charging, but says 'Not Charging'. Then I notice that the lockscreen shows '7% Charging'. Weird. Regardless of all that, the battery was not charging. The percentage never goes up and after reboots the percentage will remain the same. The battery does slowly discharge on the charger if I have it powered on.

5. I tried flashing a couple different roms before flashing back to stock and all had the same problem. I've formated /system hoping it was a problem with the OS but it didnt help. All of these charging tests were performed with the stock Motorola usb cable plugged into the wall charger. I tested the Motorola charger against my S4 to verify it works and also tried my Samsung charger on the Razr and it made no difference. However, booting the Razr M up with the Samsung charger resulted in the '?' in the battery icon and a notification in the status bar saying something about a CommServer starting. This notification was persistant and could not be dismissed. If I reboot the phone with the Motorola charger or no charger then that notification and the '?' dont appear.

6. I should also point out that I opened the phone up and disconnected the battery from the board and discharged the board. As a last resort I completely removed the battery and peeled back the tape on the bottom of the battery to expose the + and - terminals on the battery and wired it up to a stripped down charger and left it for a bit. Upon putting the battery back in the phone it showed a charge of 30% but still had all the same problems otherwise. So the battery is capable of taking a charge, it just wont take it through the phone, whether powered on or off. Thats what leads me to believe the battery itself is not bad. Its not practical for her to pull the battery to charge it, obviously. The phone detects the cable being plugged in and I can transfer files via usb cable to/from the computer no problem, so I'm fairly sure the Micro usb port is ok. Just refuses to charge.

A little lengthy but I'm at my wits end on this and really dont want to have her buy a $50 battery and then its a problem with the phone. I dont usually get stumped when it comes to fixing something but this one really has me. So if anybody can shed some light on this situation it would be greatly appreciated.