Locate the green rechargeable battery on the back plate. It is press fit into the housing near the bottom of the back half.
Trace the red and black wires from the battery to the white clip connecting them to the main power board. Pull out the white clip from the socket on the main board. This will sever the electrical connection between the battery and the rest of the lantern.
Now that the wires are removed, remove battery from housing on the back plate.