Which is better; 7.2V or 12V motor for a 3kg sumo?

Lynxmotion Rovers, Sumo, and Tracked
1

As the topic says, which motor (with same power rating) is to prefer for a standard (3kg) sumo?

I think I’ve read somewhere that it’s harder (takes longer) to stop a motor if it has a high voltage rating. True?

Or are they basically the same?

2

I always look at the RPM (speed) and torque. In this case, for the same RPM you can get a lot more torque at 12V vs 7.2V.

In my experience, motors in the 12V - 20V range can stop on a dime. I would not call 12V “high voltage” anyway.

So I’d say it’s a no-brainer unless you don’t have room for batteries. With NiMH you would need two 5-cell packs in series to make 12V. I would probably use a 3S lipo pack if I wanted to run a 12V motor.

3

That’s too broad a statement for me to agree. There are just too many different types of motors. It all basically depends on the power (E * R) you need, to do the job at hand. The more power the better for sumo. 7.2vdc motors are convenient for using 7.2vdc batteries, but they are not very common. 12vdc motors are plentiful.

4

Thanks for your answers!

Well judging from you answers it seems like a 12V motor will be the most suitable.

5

It doesn’t matter what voltage the robot is running at, as long as the robot is doing what you want it to. I have robots running at 6 volts and others running at 18 volts. Most run at either 7.2 or 8.4 volts since they are designed to use either a 6 cell or 7 cell battery pack. During a turnament, I swap batteries with what ever I happen to have charged up at the time, so they run at different voltages.

Pete

6

Well I realize that this is an older topic, but I just signed up at this forum and there seems to be a bit of misinformation floating around.

The base post says 7.2v vs 12v with the same power. Power is what governs the combination of speed and torque available. For the same amount of power, and the same rpm (as mentioned in A-Bot’s post) its impossible to get more torque at a different voltage. Now running the 7.2v motors at 12v is a different story, in that case you’d be getting 3.33x more power)

So, with power equalling voltage * current, with the same power you’ll be drawing more current at a lower voltage. This may mean higher capacity controllers, batteries, and perhaps thicker wire. I believe what governs the voltage choice is available components, and with 7.2v you’d be able to take advantage of the huge market of R/C car speed controllers and batteries.