Just remove the controller, unplug the thin red wire from switch, unplug white plug for leds, cut both black wires and both red wires from controller unit.remove controller unit. then connect red wire from switch to red wire from were battery connects, do the same for the black wire. overload protection now removed, be careful if switch is in the on position when you connect battery grinder starts!!!

It depends on the type on overload protection it has. I have seen similar equipment that has it integrated into the switch so it would be a pain to disconnect. However the only way you will know for sure is to take it apart. If you are comfortable with repairing these kinds of things it should not be a problem, but if this is something you are not familiar with it can be a daunting task.
If you get it apart simply rewire directly from the switch to the motor. If that's already the case it's integrated in the switch.

Also remember you may end up burning up the drill without the overload protector. Some cordless drills especially 3/8 are maid for long running but not strong running. My personal opinion is it's better left intact.
Hope this helps. Please let me know if you need more info.