Good tips, a diode (1N4004 or similar would keep separation between the USB 5volts and the charger 5volts. It is also a safer way to do this mode if anyone is worried. But also most USB jacks are far more regulated then any wall-wart.

The Ferrite had 0-ohms continuity to the charger pad. But I am sure I am on the right side of the ferrite, as the cap next to it is connected to the ferrite and ground.


-Off topic...
I cannot for the life of me determine how the 770 detects that the cover was put on one way or the other. There are no contacts, micro-switches, and no magnet sensors that I can find.