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Variable throttle on modified power wheels.

I have heard of other guys doing this to their kids' power wheels but I myself do not know exactly what parts to buy to make this work. I have added 2 lawn mower style batteries wired in series to give it 24 volts and it really moves! But I am worried my kids will either fry the motors or burn up the gears from receiving such a jolt when the pedal is pressed. The website tncscooters.com seems to have all the required parts but more than what I can determine which ones I need. Especially the controllers. So, what parts do I need to make the motors respond more progressively?

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You are absolutely right about damaging the motors or gears from the jolt of switching a 24 Volt battery pack on. The torque that electric motors have is huge and this can easily damage components, especially drive train components such as gears if the power is not turned on gradually.

To have variable speed control two main parts are required; a speed controller and a throttle.

For a Power Wheels with a 24 Volt battery pack I recommend using a 24 Volt 250 Watt speed controller. You could use a larger speed controller such as a 500 Watt, however this would provide a lot of Amps to the motors which could overheat and damage them. Even a 250 Watt controller could provide enough Amps to the motors to overheat them if the Power Wheels was used to go up steep or long hills or used in sand. The 250 Watt controller will minimize the chances of motor damage though. For a 250 Watt controller I recommend using Electric Scooter Parts item # SPD-24250A since it is sealed and has less chance of being damaged by water than the other 250 Watt controllers they have.

Along with the speed controller, a throttle would also be required. Both ElectricScooterParts.com and TNCScooters.com have plastic and steel foot throttles. I am not sure which foot throttle would be the best one to use on a Power Wheels. The plastic foot throttle mounts on any flat surface, and the steel foot throttle requires a rectangular cutout in the floor that it is being installed in. The steel foot throttle is the smoothest to operate and best built foot throttle between the two of them.

Since you already have the batteries and charger, the only other part I can think of that you would need is an on/off switch. I am not very familiar with Power Wheels buy I imagine it already has a power switch that you can use to turn the speed controller on and off. If it doesn't then any single pole single throw two wire on/off switch would work.

Here are links to pages that these parts are sold on:

24V Controllers: http://www.electricscooterparts.com/speedcontrollers24volt.html

Foot Throttles: http://www.electricscooterparts.com/throttlesstandard.html#footthrottle

Power Switches: http://www.electricscooterparts.com/powerswitches.html

I hope this helps with figuring out which parts are needed. If I missed a question or if you have any further questions please let me know.

 

Hey Larry,


I know your post is a few weeks old but I just joined the forum today.  


I want to add an additional answer to the ESP Support reply.  I agree with all he said but I just went through   trying to further regulate the speed of the 500W motor on the kart I just built for my son. 


You can wire in a potentiometer on the throttle signal wire. I've recently done this. Works really well. I've read on some other forums that you can't do that, but I can tell you it definitely works.  Mine is a hall effect foot pedal.  Just a simple little variable resistance piece you can get at radio shack for $2.  Get the 10ohm. You turn the dial one way and it limits the power coming down the line = slowing or speeding up the kart.


The other option is getting a controller that has one built in. I got one of those from our host here.  We won't discuss why I have had to buy multiple controllers though. :-) I made a little mistake but not related to the potentiometer though. 


good luck


Robbie

Correct me if I'm wrong, running a 250 watt controller to duel motors would cut it down to 125 each motor. The 500 would work fine. I'm running 2 traxxas 775 motors and bought the smaller controller. My motors can handle 280 watts each at 16.8 volts. I planned on pushing 24 volts.

A 24 Volt 500 Watt controller can handle a 500 Watt load continuously however will output a 720 Watt load intermittently for extra power to get up short inclines and accelerate from a dead stop. As long as the two motors connected to a 500 Watt controller were geared and used in a manner where they do not exceed 500 Watts of continuous power draw then the 500 Watt controller would not overheat and be reliable.


Keep in mind that when overvolting a 16.8 Volt motor to 24 Volts its RPM will increase by around 40% so the gear ratio may need to lowered to keep the motor running at a high RPM so it does not overheat itself, or draw too much current from the controller and overheat it.

The scooter parts website doesn't show a speed controller specifically for 18v. Will the 24v speed controller work in an 18v system?
A 24 Volt controller will not work with an 18 Volt battery pack because it has a low Voltage cut off rating of around 21-22 Volts, so it would not turn on at 18 Volts. This year we ordered 18 Volt controllers which should be arriving in a couple of months, however right now we do not currently have any 18 Volt controllers available.

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