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Discussions Question and Answer Forums Razor Electric Scooter, Bike, and Go Kart Modification Forum

Electronic brakes for Crazy Cart XL

Is it possible to modify a crazy cart xl to use the motor to provide electronic braking? Going down big hills can be terrifying without brakes and sometimes the fred flintstone method doesn't cut it.

Some Ideas / Questions:

I noticed that if the wheel is spun backwards something in the controller appears to be causing it to brake. Could I use a DPDT switch to swap the polarity on the motor and cause it to brake in forward? Is doing that going to hurt the controller? Is there a better way?

Any help is greatly appreciated.

Switching the polarity definitely works (and the motor actually reverses if you hit the throttle while stopped). If someone who knows about these motor controllers could tell me if that's going to damage something that would be great.

A DPDT switch can be wired for motor reversing, however, if the motor was reversed while the cart is in motion that would overload and burn out the controller. The best way to achieve motor braking is with a controller that has electronic regenerative braking and unfortunately, these type of controllers are not available in a 36 Volt 30 Amp version which would be suitable for the Razor Crazy Cart XL. For the last year, we have been reaching out to controller manufacturers to try to get controllers with regenerative brakes custom made for us and we have not had any luck yet but we will keep trying. 

Do you think it would be ok for the controller if I added a power resistor bank inline with the reverse path? That should dump the power as waste heat.

As long as you have a switch or relay which disconnects the controller from the motor when the resistor bank is connected to the motor then the controller will be okay. 

In case anyone comes across this in the future this is what worked for me:

I used a DPDT relay (12V coil, 36V 30A rated contacts) and tapped 12v from one of the 3 batteries. I trigger the coil with a momentary switch on that 12V.

The motor + and - wires get connected to the relay common.

The controller + and - wires get connected to the relay normally closed contacts.

The resistor bank gets connected to the relay normally open contacts.

For a resistor bank I used 6 1 Ohm 100W power resistors. I wired them into 2 banks in series of 3 resistors in parallel.


It works very well and I can go down my fairly steep driveway without feeling like I'm going to die.

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