Installing brake switch and wiring light and fans

The controller came with an input for a brake switch. This activates the brake lights (which I didn't install) and cuts power to the motor during breaking. This is important so that the motor doesn't get damaged by an inexperienced rider who presses both pedals at the same time. The video shows how it works. The switch "Mechanical Rear Stoplight Switch | 2400115" was ordered from J&P cycles for $6.99.

The other thing I wanted to discuss was how to wire a 12 volt light to a 36 volt circuit. One way would be to wire it directly to one of the 12 volt batteries, however, it would have to be switched independently  would require more wiring, and would deplete one of the batteries faster than the others. What I decided to do is as follows: I wired a 12 volt fan and a 24 volt fan in series to the power indicator wires from the controller. I then wired the light in paralell to the 12 volt fan. I checked the voltage with a voltmeter across the 12 volt fan and it was slightly less than 12 volts. The light works fine. Here is the circuit diagram:

The go kart works really well. The fans keep the controller and motor cool. The batteries seem to last pretty long. The kart handles well. It has reached a top speed of 20 mph on the street.

The only minor issue I have noticed is that the chain doesn't seem tight enough and it is a bit noisy. I will probably have to use some washers to elevate the motor in order to tension the chain. Alternatively, I could use an idler pulley to tension the chain. Example: