Using two BRUSHED motors on one controller??

[RLT]

Ok, I can see why you wouldn't want to used two brushless motors on a single controller, due to phase synchronization and whatever other issues, but is there any real good reason that you shouldn't run two brushed motors in parallel off of one controller,... assuming that the controller has enough current capacity to to handle them both, of course..

I've tried it 'on the bench' with only a light load and it seemed to work fine in parallel..... In series, they played some neat tricks, working kind of like a slipping differential on a car, but in parallel it seemed to be pretty well balanced with the load I could put on by hand... (about 5A).

But since I haven't gotten around to actually getting 'wheels on the ground' for any of my intended projects, I'd appreciate any input on this concept before I waste too much time messing with something that won't work.

 

[Patrick]

Sure, this is fine. In fact, some people switch between series and parallel, depending on whether they want power or speed. The prallel choice is a little bit easier, as you don't have to match parameters so closely.

 

[rkosiorek]

people do it all of the time. look mat the classic EV Warrior. 2 motors 1 controller. another example of this is the Kill-A-Cycle drag bike

most of these designs use motors with mechanically connected shafts so the motors turn at the same speed.

rick

i just realized that last friday was my anniversary on this site. Yipeeee!!!

 

[fechter]

No reason you can't run two brushed motors. I've done it on several RC models. Just make sure the motors are the same, and if one is running backward, you may need to tweak the brush timing to match the other one.

With dissimilar motors, you can do it, but it gets much trickier.

You can run them either series or parallel.
In series, they both get the same current, and run half as fast as a single motor.

In parallel, each motor gets half the current, but they run the same speed as a single motor.

Since a typical controller is current limited, two in parallel will behave just like one motor as far as speed and power at a given current limit. Since you have two motors, you can run twice the current limit as a single motor, but if you switch to series, the limit will be high enough to possibly fry the motors. I think this would only happen if you really stall the motors or are drastically overgeared.

In series, they behave like a differential as you observed. In parallel, they behave like a limited-slip differential. If both of them are attached to the drive train, they will tend to share evenly.

 

[Johnbear]

I have done it on an e-bike, worked great. The bike weighed a ton with the two hub motors. It went pretty fast too. I did not like the weight so I now have the two motors not doing anything. I think I will sell them in the spring.

 

[RLT]

Thanks for the confirmation everyone. I appreciate it.....

Now if I can just get the time, the energy and a few bottles of propane to heat the workshop during these 0ºF nights, I might be able to dig out the MIG and build something with wheels on it..... Or at least a battery rack and motor mount for that $10 thrift store 10 speed that I was going to use for a test bed for the lower voltage motors.

That 130V motor / controller combo is going to have to wait a lot longer, as It is going to need a frame more like a go-cart (or a long three wheel scooter) than a bike, Just to hold the SLAs.

 

[cware05]

I have now been donated a bundle of powabyke 250w brushed motors and have enough to make a 26" wheel tricycle up.
Can I run one shared 48v battery, one throttle and one controller to power 3 motors in parallel (one would run backwards) by just joining up the power leads to the motors and just let them sort out how much current they all need ?

 

[amberwolf]

Should work. How well they share depends on the differences between the motors (they're never completely identical) and the differences in loading on each.

The one you need to run backwards, you just connect it's power wires reversed from the other two.

Keep in mind that if the motors were made for a lower voltage, brush arcing will be hotter at the higher voltage, and waste more power as heat.

Unless you add extra cooling to them, I'd generally try to work out total current limiting at the controller so it doesn't allow much more than the total wattage of all the motors' rated wattages, because if they're not sharing well you'll be pouring a lot of power into one or two, and heating them up a lot. The only easy way to tell which ones are getting more current is to monitor their temperatures; the hotter ones are taking more.