I need help slowing down a remote control car.

Thread Starter

GutoSoares

Joined Sep 25, 2020
5
So, i attached a 12v battery to a remote control car to make a model. The model has a switch that turns the car on, however, the 12v makes the car spin insanely fast, so i am now trying to slow it down. I tried reducing the battery voltage to 9v using a few resistors, but for some reason the car did not even start up. Then, i tried reducing the battery voltage to 6v, and still nothing. A while later, i made an improvised 7v battery using two 3.7v LIPO batteries. I connected both in series and once again, the car didn't start up. After that i made another 7v battery, and connected it to the other 7v battery to double its amperage. After doing that, the car started up. I then tried to do the same thing to the 12v battery (connect both in parallel to double their amperage) and then reduce their voltage, and it didn't work. Can anyone help me? (by the way, im an absolute newbie with electronics).
 

MrSoftware

Joined Oct 29, 2013
1,912
Read the docs on the speed controller. Some turn the car off when the battery discharges past a specific voltage, to prevent damage to the battery. Some models also allow you to adjust the cut-off voltage. You have to read the docs to see what you're working with. Or start googling the part numbers or model numbers if you don't have any docs.
 

Thread Starter

GutoSoares

Joined Sep 25, 2020
5
Read the docs on the speed controller. Some turn the car off when the battery discharges past a specific voltage, to prevent damage to the battery. Some models also allow you to adjust the cut-off voltage. You have to read the docs to see what you're working with. Or start googling the part numbers or model numbers if you don't have any docs.
Im gonna search for the docs, but i don't think it has any. It is a cheap AA battery remote control car
 

Audioguru again

Joined Oct 21, 2019
1,914
You do not use a resistor to slow an electric motor. The motor is stalled when it starts and then it draws a very high current. The high current will simply heat the resistor and the motor does not start running. Also with a resistor then the motor will slow down and maybe stop when it has some work to do.

Your 3.7V Lithium batteries probably were not fully charged (to 4.2V each).
An electric motor speed controller uses Pulse Width Modulation (look in Google for it).
 

Thread Starter

GutoSoares

Joined Sep 25, 2020
5
You do not use a resistor to slow an electric motor. The motor is stalled when it starts and then it draws a very high current. The high current will simply heat the resistor and the motor does not start running. Also with a resistor then the motor will slow down and maybe stop when it has some work to do.

Your 3.7V Lithium batteries probably were not fully charged (to 4.2V each).
An electric motor speed controller uses Pulse Width Modulation (look in Google for it).
Oh, so is there another way to make it run slower in the 12v battery? By the way, i forgot to mention: the car will be in a platform, it will not move.
 
Last edited:

MrSoftware

Joined Oct 29, 2013
1,912
Ah ok, then I'm siding with the comments above about resistors, you're probably using too big of a resistor. You can use a low impedance power resistor, but it's going to waste a lot of energy to heat. Some sort of PWM DC motor controller would be more efficient. What are your requirements, are you able to install a whole different motor controller if you need to? There are PWM motor controllers for cheap at stores like eBay, something like this would probably work, assuming it fits your needs (you lose the remote control capability, is that OK?):

https://www.ebay.com/itm/6V-12V-2A-30W-DC-Motor-Speed-Controller-PWM-Adjustable-Variable-Driver-Switch/121924096947?epid=1438777904&hash=item1c633e13b3:g:odEAAOSwfZhXNWjA
 

Thread Starter

GutoSoares

Joined Sep 25, 2020
5
Ah ok, then I'm siding with the comments above about resistors, you're probably using too big of a resistor. You can use a low impedance power resistor, but it's going to waste a lot of energy to heat. Some sort of PWM DC motor controller would be more efficient. What are your requirements, are you able to install a whole different motor controller if you need to? There are PWM motor controllers for cheap at stores like eBay, something like this would probably work, assuming it fits your needs (you lose the remote control capability, is that OK?):

https://www.ebay.com/itm/6V-12V-2A-30W-DC-Motor-Speed-Controller-PWM-Adjustable-Variable-Driver-Switch/121924096947?epid=1438777904&hash=item1c633e13b3:g:odEAAOSwfZhXNWjA
Oh yeah, i forgot to mention, the car is going to be fixated in a base plate, and it is supposed to just turn on with a switch. I do not need the remote control part working
 

camerart

Joined Feb 25, 2013
2,109
Oh yeah, i forgot to mention, the car is going to be fixated in a base plate, and it is supposed to just turn on with a switch. I do not need the remote control part working
Hi G,
Are you able to open up the car and take a photo, so we can see the workings?
Camerart.
 

Tonyr1084

Joined Sep 24, 2015
5,070
Wire a battery directly to the motor. Use a switch to turn it on and off. If the motor is designed to run on 12V and you want it for display only, using 6V, 4.5V or less will spin the wheels slower. You might - depending on the motor - be able to power it from an old cell phone wall wart.
 
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