Time to take in some considerations about the power supply of MARB. I am using a 9.6 V, 5000 mAh NiMH racing pack battery. Obsolete, you will think. Why not using a Li-Ion or Li-Po battery? I can tell you. NiMH batteries are much easier to handle than Li-Ion or Li-Po batteries. They forgive mistakes Li-Ion or Li-Po batteries won't. They may have less energy capacity and a memory effect, but they normally don't burn or explode when treated the wrong way.
Battery mounted on the robot:
3-D printed bracket for the ON/OFF switch:
Another 3-D printed part for the power distribution and motor control module: