Speed limiter for elec. kids bike

[gasser]

Found a cheap source for 12v electric kids bike but need someway to limit the top speed to 2-3mph. Any suggestions?

 

[pscook]

Maybe a resistor or potentiometer of some sort? I would assume that the "throttle" directs "X" amounts of volts to the motor controller, maybe measure amount of volts required to go 3 MPH, and get a resistor that matches that amount?

Can you share this source with some of the specs of the controller unit?

 

[gasser]

Can you share this source with some of the specs of the controller unit?

I'll see if I can get more info on the controller.

 

[Zman]

Put in a 6v battery.

 

[Zman]

Another option maybe to put a 12 head light bulb in series with the motor lead.

 

[pscook]

Another option maybe to put a 12 head light bulb in series with the motor lead.

Or at least a light socket with a bunch of different bulbs to swap in. "It's great traction today, better install the 35w bulb." "It's raining out, probably want the 55w for better traction in the clay."

Seriously, a light bulb would do the trick; however, it would drain the battery faster as it is a constant load on the battery. You would need something that limits the power to the throttle or between the throttle and the motor controller.

 

[Zman]

I like the socket idea, but wiring the bulb in series with the battery and motor, will add the resistance of the bulb to the circuit and it will reduce overall current flow. It will split the available battery power between the light and motor. The drop in current flow will make the battery last longer.

If you wire the bulb in parallel with the motor you will reduce the battery life and it will have much less of the desired effect to reduce motor power(unless you choose a high power bulb that draws so much power from the battery that it drops the voltage but that will drastically reduce battery life.

 

[pscook]

I like the socket idea, but wiring the bulb in series with the battery and motor, will add the resistance of the bulb to the circuit and it will reduce overall current flow. It will split the available battery power between the light and motor. The drop in current flow will make the battery last longer.

If you wire the bulb in parallel with the motor you will reduce the battery life and it will have much less of the desired effect to reduce motor power(unless you choose a high power bulb that draws so much power from the battery that it drops the voltage but that will drastically reduce battery life.

Let me see if I understand this-

Series: Wire the bulb so that it is between the battery and motor (and after the controller), thereby interrupting the juice to the motor with the bulb, diminishing available power to the motor, which makes both voltage draws compete for power;

-or-

Parallel: Wire the bulb in a parallel circuit with the motor (so that it is constantly lit regardless of throttle position and throttle to motor circuit is uninterrupted) and thereby just draining the battery and not affecting the overall operation of the motor draw.

Seems like you could wire in a socket on the Series scenario and add or remove wattage through bulb draw, as a higher wattage bulb would draw more power per throttle setting, all things being equal and constant (not an engineer!).

 

[Zman]

That is pretty close, except the higher wattage bulb would actually put more power to the motor because it is less resistance and it would allow more current to flow through the over all circuit.