Unscrew one (1) Torx T9 screw on the side top.

Unscrew four (4) Torx T5 screws around the side of the housing.

The Torx screwdriver needs a long, narrow extension; the screws are in deep inserts.

After all five (5) screws are removed, use a rigid spudger to pry open the battery housing from the controller handle.