How do I know what voltage of battery I need for two 12 volt motors for a RC Car?

Projects General Guidance
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Being an arduino noob with only a couple tiny projects under my belt that used the arduino for the power supply, I wanted to tackle trying to make my first RC car. Without thinking the kind of battery I’ll need to match to my motors, I blindly bought a couple 12 Volt electric motors off amazon.

Here’s the link for them:

I bought the motors and everything else that I needed to make the project except for the battery as I now realize that choosing the right battery is a challenge of its own. What do I need to do to figure this out? Sorry if this is a dumb question. All advice is appreciated.

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Forget the batteries for now

How fast do you want the car to move considering that the motors appear to be very geared down and only rotate at 100 RPM ?

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And for how much time do you want the car to operate between charges, if you use rechargeable batteries?

Paul

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How do I know what voltage of battery I need for two 12 volt motors for a RC Car?

Uh, 12 volts?

The motor will run at 9V or even 6V, but it is rated at 12V, so I would use a 3S (3 cell) battery which has 11.7 to 12.4 V at full charge. You do have a LiPo charger, don't you?

Which size battery (in mAh) depends on the current draw of the motors and how long you want to power them. This motor is rated at 1.1 Amps. So, if everything is nominal a 2200 mAh battery (2.2 amp-hours) will power the motor for two hours. But in the real world, you would be doing good to get 75% efficiency, or 1.5 hours.

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Thanks for the info! Will I need a 3S battery for each motors or is one 3S battery good to power both at the same time?

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Thanks. I guess I’ll have to purchase a couple new motors with higher RPMs as I didn’t know 100RPM was slow haha

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Since the motors are driving the tires look at tire size, the bigger the tire the faster the car.

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Same formula. How long do you want them to run? If one battery is good for 1.5 hours on one motor, then two should be good for 3 hours on the same motor.

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I would like both motors to run for at least an hour. To calculate how long a battery can power two 12 volt motors, how would I go about this? Is there a specific formula? I’m a grade 12 student and I’m pretty good at math but I don’t know where to find and which values I need to take into consideration and how to use them to find myself the answer. If you could point me in the right direction Steve, that would be much appreciated

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Also, I was wondering how you figured the motors will deliver 9 volts to 6 volts when it says it’s rated at 12 volts— am I missing something?

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I gave you the formula above; it's pretty simple. Amp hours of battery capacity divided by the current requirement of the motor gives you the time. (AH/A=H)
Reduce it by 25% because 75% efficiency is good. 100% is impossible.

My experience with DC motors is that they will still operate at half of the rated voltage, though slower. In fact, varying the voltage is one method of speed control.

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Hi Steve,
I don’t have a lipo battery charger but if you think it would work better for my project, I’ll ask my dad if we can buy one. Though, I am wondering, could I run eight AA alkaline batteries in series instead? Googling it, it shows me that the batteries offer approximately 2500mAh of battery capacity and together it would supply 12 volts (1.5 volts per battery). My dad has lots of these batteries and it would be cheaper than buying a 2200mAh 3S Lipo battery and a charger for it.

Thanks,
Ryan

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You can use any battery technology you want. Of course, eight AA batteries will be as bigger than the same power capacity of LiPo. Maybe you can upgrade later if you get tired of buying AA batteries in bulk.

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