[rfsancho]

Hello! Pardon my first post being an issue and not an introduction.
So the story goes like so~
I have two boys, 1.5 years apart, oldest almost 5 now. A year ago we got them a power wheels, and they absolutely loved it, whereas I hated it mechanically. It was so shoddy, so weak, the motors burned out left and right, steering didn't have proper geometry, wheels were hard plastic. They burned out motors and control boards left and right by racing it around in dirt and grass.
So I redid it with dual 350 watt bicycle motors driving their own rear wheel via chain with a pwm controller for each inputted via a single potentiometer pedal. And the original pedal off/on clicks the controllers off/on as to "brake" (abrupt but does the job). It's pretty solid if I say so myself, welded frame and everything with the original plastic shell of the powerwheels on top to look kiddy. I ride it with them occasionally, very fun.
The controllers are great, motors are great, pedal is great. At 36v battery it can crawl or go fast as a normal car. But herein lies the issue. I had to put a switch to toggle input to the pwm controllers from either a 36v source or a 12v source. Kids are kids, they go pedal to the metal, though the oldest is trying to learn the pedal a bit. Definitely easier to just hammer it down. The switch to 12v is needed to go slower since they don't have the footwork down yet.
I don't like having the switch from 36v to 12v, as I'm sure it heats up the motors more than it should, is less efficient, and a lot less power than same rotational speed on 36v. ( I may be wrong). And having different voltage sources on the car just weighs it down, makes it a pain to charge, and there just isn't a lot of places to put batteries on this thing.
What I want to do is somehow limit the potentiometer pedal output electrically. Maybe with resistors or another potentiometer in line with pedal? Though maybe that will just give a dead zone to the pedal travel. I just don't know. Searching these forums came to no avail to doing something of this sort. And googling online doesn't help much either.
I need to somehow, at the throw of a switch or turn of a knob, have the pedal output different resistance as to simulate lower speed ceiling for the motor controllers. All while still keeping the full sweep of the pedal working with no dead zones.
It feels as if there is a super simple solution, but I can't get my head around it.
Any help is greatly appreciated.
Here are some pics of the car when it was starting to get work done. It's been a tad bit updated since then but the electronics remain the same.

 

[Darwin12]

Hi, I read all your requirements that you want to upgrade power wheels. To modify this electric kids car you need to modify the battery from 12v to 24v. Fix the electronic speed controller in your power wheels. It automatically controls the battery as well as wheels. At last, you need to do the custom fabrication process. You should add more traction to the tires so that your power wheels move fast.

 

[rfsancho]

Hi, I read all your requirements that you want to upgrade power wheels. To modify this electric kids car you need to modify the battery from 12v to 24v. Fix the electronic speed controller in your power wheels. It automatically controls the battery as well as wheels. At last, you need to do the custom fabrication process. You should add more traction to the tires so that your power wheels move fast.

You didn't read anything I posted did you?

 

[BAstereo]

You didn't read anything I posted did you?

Lol, I read your initial post and was quite confused by that response.

Very nice build, looks like a blast for the kids!

I think your solution is to modify the throttle.
If you limit the throttle signal to some percentage of full throttle you should get your desired outcome.

The easiest would be a block under the pedal stopping the throttle at 50% or whatever.

But, if you want full travel on the pedal you'll need to do something electric.

A resistor with a switch to bypass it and allow full throttle would be my recommendation.

Is your throttle 2 wires? I think a variable resistor inline should do it, unless low resistance is no throttle.
3 wires? Put the resistor either on the power or ground depending on the pedal set up.

 

[rfsancho]

Wouldn't a resistor create a dead zone on none and full throttle end? Since it's raising the resistance of the pedal. Since the signal will only pass through certain resistance range? So the initial press will have a small dead zone and so all full throttle. And with a big resistor to lower output to let's say 30% it will have very large dead zones of no signal. If I'm wrong, do correct me.
This will certainly give me the outcome that I want but I don't want to sacrifice pedal travel zone for that.

 

[BAstereo]

You might be right.
But in my mind the throttle is just a variable resistor with a range for example of 0 ohms to 1000 ohms. But, the controller actually looks at the voltage through the throttle, different controllers monitor this on different ways. A cheep variable resistor and you could test this idea.

The other option might be to get a throttle out of a car that has two internal sensors where one has half the output (double resistance) and switch between the two sensors to change from kid mode to adult mode.
I typed all that out only to realize you could just add a second sensor (with a different resistance range) onto your current pedal...

Or a controller with a programmable limp mode mode and use limp mode as kid mode. But, I don't have any examples of these controllers outside of something like an expensive Curtis or Sevcon. So, it might not be feasible.

 

[rfsancho]

A pedal with two pots for different ranges sounds too good to be true, but I'll definitely look into that, thanks for the idea. A controller that does this exists which I will be using on the dune buggy build and I already have some prices, though they are steep as I will be needing two of them for the two motors.
But for this little car I want the lightest and cheapest solution.
Thanks again for the ideas.