There are two ribbon cables in the way of the battery that must be removed.

The smaller ribbon cable is wrapped around the top of the battery and inserted into the circuit board. Use tweezers to free the cable and detach it from the board.

The larger ribbon cable is attached from the back of the grip panel to a wider connector on the circuit board, held down by a black connector lid.

Use a thin, flat spudger to lift the connector lid, then pull it out from the circuit board to disconnect the grip panel from the conntroller.