24v DC motor control. Looking for ideas.

[alchemysa]

I have been given an old 'Shoprider' mobility scooter similar to the one in the pic. (Over here we call them Gophers).

I want to turn it into an electric 'tractor' for the grandkids to play on. I've stripped it back to little more than a chassis, wheels, 24v electric motor, batteries and handle bars.

My problem is how to control the speed. These mobility scooters normally have quite a complicated and expensive electronic speed control unit near the motor, linked to a mass of switches and circuitry in the dash panel. In my case ALL that has gone in the bin. (It didnt work and was too expensive to replace.)

I bought a relatively inexpensive 24v 50 amp DC PWM motor controller linked to a 'Hall effect' twist grip throttle. It operated smoothly but its failed twice, and when that happens the controller stops 'pulsing' and the gopher takes off at full speed. I just don't trust this set-up for the kids.

I know DC motor pulse controllers are efficient but I think I just want something safer and more durable even if it is less efficient. If something fails I want the gopher to stop, not take off! So can anyone suggest a simple and cheap way to control the speed?

(While I'm typing this I just noticed my wife's sewing machine foot pedal sitting on the floor. Maybe an old one of those would do the job?)

Or can I get a cheap DC speed controller that is fail safe?

Any suggestions would be appreciated.

 

[MossRoad]

Look for an electric golf cart in a scrap yard.

 

[weedpharma]

I have been given an old 'Shoprider' mobility scooter similar to the one in the pic. (Over here we call them Gophers).

I want to turn it into an electric 'tractor' for the grandkids to play on. I've stripped it back to little more than a chassis, wheels, 24v electric motor, batteries and handle bars.

My problem is how to control the speed. These mobility scooters normally have quite a complicated and expensive electronic speed control unit near the motor, linked to a mass of switches and circuitry in the dash panel. In my case ALL that has gone in the bin. (It didnt work and was too expensive to replace.)

I bought a relatively inexpensive 24v 50 amp DC PWM motor controller linked to a 'Hall effect' twist grip throttle. It operated smoothly but its failed twice, and when that happens the controller stops 'pulsing' and the gopher takes off at full speed. I just don't trust this set-up for the kids.

I know DC motor pulse controllers are efficient but I think I just want something safer and more durable even if it is less efficient. If something fails I want the gopher to stop, not take off! So can anyone suggest a simple and cheap way to control the speed?

(While I'm typing this I just noticed my wife's sewing machine foot pedal sitting on the floor. Maybe an old one of those would do the job?)

Or can I get a cheap DC speed controller that is fail safe?

Any suggestions would be appreciated.

Try Oatley Electronics in NSW, they have some control kits for dc motors in scooters and they may be suitable.

Weedpharma

 

[alchemysa]

Thanks for the replies.

In the end I went back to the supplier of my small DC controller and upgraded to their super heavy duty model.
12V-48V DC Speed Controller 75A-100A Case Model

It cost the best part of $100 but it should do the job easily.

For your info, the designer and maker of these controllers tells me my original failure is common to all these types of DC control gadgets. When they fail (caused by too much current draw) they usually short out inside and send full uninterrupted power to the motor. There's no solution other than using a much heftier unit and adding a big kill switch, which is what I will be doing.

Mobility scooters have much more sophisticated, more expensive, programmable controller/ECU's that monitor various functions, apply the brakes, and kill the power in the event of a failure. Thats all too much for the 'toy' I'm building.