[Nexus 4 Q&A, Help & Troubleshooting] cetkat:
So, I plugged my Nexus 4 into a generic car charger and it went black instantly. The battery was at about 92%. With the hope that a proper AC or computer USB charge connection would bring up the white battery icon and fix things, I stopped by an out of town T-mobile. The manager tried the button battery-reset (up volume + power for 60sec) and I googled alternatives and tried the - enter recovery by pressing those buttons for 15sec off the charger and connecting while still holding down the buttons - trick. Neither worked.

The manger seemed familiar with that and the other button pressing tricks, and said that really, my only real hope would be to reset/replace the battery, but that would void my warranty. However, although the T-mobile site claims my Google bought phone is under warranty (and I've been paying for it each month), technically, it isn't. Under them or Google (any more). So, I purchased the tools to open the phone, as well as a replacement battery. In the interim, I tried to use all the button combos and various charging connections to get it to come back to life. I *did* manage to get it charging the old battery. I know because the blinking red light turned constant for an hour or two, and the battery got warm. I can only guess that the battery was too damaged to keep the charge however, because I could never get it to turn on during or after. My best guess is that the software battery reset allowed the phone to send a charge to the battery - at least once.

After getting my tools and replacement battery, I managed to get the phone open (with great effort - I think there must be a difference between batches there). I removed the old battery connection and looked to see if I could get the charge icon with it unattached and on the charger. I couldn't. Reconnecting the old battery didn't seem to make any difference.

I was about to go through the process of prying up the old battery when I realized that you can actually connect the new battery to the board connector without getting the old one out. So I did that. Leaving it charging like that for awhile didn't do anything, so I decided to do another software battery reset and I'm letting it sit on the charger overnight. All of this has been without reattaching the back.

So my major question is - does anyone know for sure if the phone actually charges the battery with the back off? I know there are important circuits there - which seem to shut down the phone after the battery or google image when not detected (at least that's my deducement after reading posts). But are those connections also used in charging? The Qi goes though the back to the charger function, so perhaps that connection has to be there? I would like to try and find out though beforehand. It took 2 hours and two mangled guitar picks to get it open the first time, and the second may be just as trying. (And believe me, towards the end, I was not concerned with being gentle.)

I am also curious about the four prong battery connection. I've seen the post about charging the battery using external sources by connecting to the two outer pins. Does that mean the two inner pins constitute a second circuit between the charged battery and the phone? And if I find another 3.8v battery fully charged, I could perhaps connect that to the phone instead by wires and get it booted into recovery? As to why I'd want to do that, I don't recall the last dated CM version I had installed, so finding that in their folder plus pulling off everything from /data... assuming I replaced this with another Nexus 4, I might be able to save myself a lot of setup hassle.

In terms of the red light... it actually seems to be an error code. When triggered, it blinks 7 times, and on the eighth stays lit for a bit before repeating.