With the earpiece removed, we can get access to the battery charging terminals. Identify the location of the cell positive and negative terminals.

The negative terminal (cell ground) is a large soldered tab. The positive terminal is the second lead from the square IC chip.

Remove the silastic wire bonding to expose the ground and positive lead. De-solder and tape back the cell positive ground to protect the unit's electronics from the charging current in the next step.

Solder appropriately colored wires on to the two terminals.

Check battery voltage, it should be at or near 0V.