Step 2: Drill a hole in the case, near where the battery wiring harness enters the battery chamber. I used a 1/2" drill bit for this.
Step 3: Make a grommet. I used some silicone air hose for my aquarium, cut a length of it, then split it. I used a few separate pieces.
Step 4: Re-assemble, Hook up a much bigger battery than what's supposed to be inside.
I accept no blame for any of the many things that could possibly go wrong with this.