Dynamic Braking - Resistor?

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e-doggies
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Dynamic Braking - Resistor?

I've been thinking about "experimenting" with dynamic braking on a little Schwinn scooter. I know it is not practical, I just wanted to try it for fun and to learn something new.

My scooter with batteries and rider weighs less than 275 pounds. I don't go over 20 mph. I can already lock-up the rear wheel with the disk brake at full speed, so, once again, I certainly don't NEED dynamic braking. I have a 36V 750W Permanent-Magnet Brushed Stock Currie motor. I overvolt the motor to 48V from a YI-Yun LB37 Controller.

I was thinking about using a 6-terminal solenoid, and a brake lever with a switch, to disconnect the negative between the controller and motor; and connect the negative motor lead directly to the positive motor lead to quickly slow down.

My question is: Do I need to use a resistor, or will it not matter at all in my case? If I was to use one to regulate the rate of braking, how would I know what resistor to get? Specs? Is there any risk of harm to any components if I do NOT use a resistor?

I appreciate any and all comments. Thanks.

marylandbob
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Re: Dynamic Braking - Resistor?

By all means, USE A RESISTOR!--A resistor of about 2 to 4 ohms, rated to handle 500 to 1000 watts should be OK. Attempting this without a resistor will give extreme braking, and is likely to damage the motor commutator and brushes, and heavily stess the mechanical drivetrain. The resistor will require mounting in a place where its heat can safely be dissapated, as activating regenerative braking at speed on a long downhill will generate noticable heat.--If using the 4 ohm resistor, 500 watts is OK, but the 1000 watt resistor should be used if using 2 ohms. Lower resistance equals stronger braking. On wet/slippery surfaces, strong braking can be dangerous!--Bob Curry

Robert M. Curry

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Re: Dynamic Braking - Resistor?

Thanks for your detailed answer, Bob. Looks like that resistor is a bit expensive. I don't want to damage my motor or drivetrain, so I guess I'll just stick with my disc brake for now. Thanks again.

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