Diagnosing charging on Droid 4
A friend gave me his Droid 4 which had a balooned battery. I ordered a replacement, and it displayed a question mark on the battery. I tried charging overnight,
and it wouldn't turn on.
I checked the battery and it was dead dead 0.1v.
Plugging the phone usb port into a charger, I checked the voltage between the battery terminals.
With the phone terminals at the bottom, the bottom left screw appears to be connected to ground (and the shields for all the modules on the PCB.
measuring between that and the next spring terminal I get 2.7 V, and between screws, 2.7 V
I'm pretty sure the battery is a standard 3.7V lipo, so this wouldn't be enough to charge it, unless there's some way the battery is actively involved in the circuit and the actual voltage goes up when a battery is attached.
I'd like to confirm that the charging circuitry is ok before I risk ruining another battery.