Turns out the droid4 is very tolerant of 'diverse' batteries. Even with stock android.
The simplest connector i found was to take a sharp knife to a wire, poke a hole in the middle, and push the torx bolts through it. Positive end goes to the outside of the case.


Result: 1040 mAh to 3800 mAh
http://0x0.st/-fL4.mkv
Yes a back cover was sacrificed!