Triple motor setup with differential voltage across 1 motor

I have a ebike with a triple motor setup for added torque/speed. All 3 motors are a unite my1016z 24v 350watt geared reduction motor. All motors have a freewheel system hook up on their shaft.
I have a switch on the bottom motor that is closest to the star wheel/chain ring so that I can engage and disengage the motor. At all times the 2 top motor are always spinning and whenever I click the switch the bottom motor switches in.

The problem I'm having is that whenever the switch is turn on and the bottom motor is engage I don't feel any difference from the bottom motor, there is no added torque or speed. It's almost like the motor is not contributing to the overall speed or torque of the bike that the 2 top motors are producing. So basically its just wasting energy with no improvement on my riding condition.

When I had just two motor setup with the switch on the bottom motor closest to the star wheel/chain ring, whenever the top motor is running alone and I click the switch to engage the bottom motor I could feel the added torque or speed. The bike runs faster and it also climbs hills easier but now with the 3 motor setup whenever the bottom one is engage there's no difference. I'm still experiencing just the power of the top 2 and no power from the bottom one. I was expecting to get more torque/speed due to the fact that is 3 motors are now running instead of 2.

What I am asking is that suppose the bottom motor is powered with a higher voltage(36v/48V) than the two top motor would i feel the difference in terms of speed/torque when the bottom motor chips in?

Would this be wise?

Would the bottom motor now spinning faster than the other two cancel out their performance? and basically it would just be the bottom motor carrying the load now?

Is there another way I could install the setup to use the same 24v volts across each motor and feels the difference whenever the bottom one is engage?

Someone was telling me that the chain would have to be mount a special way on all 3 motors so I can feel the difference, is this correct?

Please give me some tips on what i can do or what you think.

I anxiously await your comments.

That is too many factors to consider and too little information to troubleshoot.

The first thing I would check is Amp draw: No use for a third motor if all three of them together are not fed more total power than two.

IMO, you have a system that is redundant: Too many components for the purpose. Why to build with 3 motors when you could have more power and speed with one. A simple 3 speed switch could replace all that hardware.

If you need adequate troubleshooting, please post pics and/or mechanical and electric wiring diagram.

Not knowing how you have things physically and electrically connected, it's tough to say what might be wrong (if anything).

It could be something as simple as the bottom motor is a slower wind than the others, so that even at the same voltage it runs slower than they do, and thus is never fast enough to provide any drive power.

If you have separate controllers for each one, then you can simply use a lot less throttle on the first two and then engage the third, and see how much it contributes that way.


If they are all simply paralleled on one controller, then if the third motor is not the same resistance as the others (different winding) then it'll have a different current flowing thru it.

If they are all in series on the same controller, then it'll have the same current, but might have a different voltage across it.



As for using a higher voltage on one motor vs the others, then yes, it'd take more of the load if it spins faster. Thats' the problem with mulitple motors on the same system; anytime one motor runs faster than the others, it takes more of the load than the others. if it is no more powerful than the others and not powerful enough to do all the work, it will slow down so the others will "catch up" and do some of the work, too, but it will also get hotter than they do, as more of it's power is being wasted as heat instead of applied to the wheel as work.


If you had individual controllers for them, and individual throttles, then you could adjust each throttle for just enough power so each is taking an equal share of the load. An MCU could be programmed to do that (based on current thru shunts in each controller) from a single throttle, or a relatively simple op-amp or transistor circuit could be designed to do the same thing. Someone may have already done that part for two motors, and it could likely be adapted for three.

I will post some pics of the setup so you can comment further.
Thanks for the responses so far.

Each motor has a maximum speed (RPM). If the first two motors are already spinning above the speed that the third can go, then it can't make a contribution. You need to figure out how fast each motor can spin. You can increase the speed of the third motor by increasing its voltage, which requires a separate battery. That's easy to do if you're using lipos. In mine, I needed lower speed for the crank motor, so it had a 12S battery, while as the front and rear motors were 16S.

The 3 motors are the same as I stated above. The max rpm of each is about 420RPM. So therefore if I power the third motor with a higher voltage I will get a higher speed/torque when that motor is chip in while the other two are running off the 24v rite?

And has the post stated above the bottom motor will be carrying most of the load due to the fact that its spinning faster?

Another setup I was thinking about is instead of the top of the chain connected to just one of the motor which is the one at the top I would route the chain so that the top of the chain coming from the chainring is connected first to the bottom motor then goes to the 2 then 3rd motor after which the chain would then make a turn until it comes back to the bottom of the chainring. In all the routing the top part of the chain would be connected to ample amount of teeths on each motor freewheel.
Would this make a difference in terms of contribution from all 3 motors?

The reason why I asked this is due to the fact that currently the top of the chain is connected to just the top motor while the other part of the chain which is the bottom makes it way around the 2 and 3rd motor and I notice that at all times the top motor is doing most of the work as it gets the hottest especially when climbing hill. So I was thinking that maybe if the top of the chain coming from the top of the chainring gets to be attached to all 3 motors then it would make a difference in terms off all 3 motors would now be contributing. So just tell me what you think about my theory.

In regards to powering just the 3rd motor on a higher voltage how could I set it up so that I have my 24v lifepo4 running the two top motors and the 3rd motor running on 36v stills get to run from the same controller with one throttle operating all 3?
I was thinking that the 2 wires(+ & -) running to the 3rd motor i would run to a step up converter that takes the 24v coming in and push it up to 36v or 48V. Is this a good idea? Or tell me what you suggest I do please.

If you run one motor at a higher voltage, the 2 other will start to help only when the fast one lags to their speed. This will cause serious overheating problem. You should feed them all 3 at a higher voltage, making them spin the same speed. That is why I say your system is redundant: One bigger motor would do better than the 3 small ones, and a simple 3 spd switch would replace advantageously all the extra hardware.

what exactly do you mean by installing a 3 speed switch?
how would i install it?
In what way would this replace most of my hardware? I'm kinda lost to the 3 speed concept.

Sorry, ignore what I said above. I didn't read your first post properly. I didn't realise that you have three motors driving the same chain.

fabieville said:

what exactly do you mean by installing a 3 speed switch?
how would i install it?
In what way would this replace most of my hardware? I'm kinda lost to the 3 speed concept.

Click to expand...

One motor requires less hardware and wiring, making a simpler chain line that is more efficient with better reliablility. Also, for the weight and volume of your 3 motors, a bigger one will give you more power than your 3 together.

Then, if you want to ride with less power some times, or to cruise at low speed, you set the controller for a 3 speed switch mounted on your handlebar, that will limit current and speed to your presets for positions 1 and 2, and full power for the third speed.

My suggestion is to dump the brushed motors and get one capable motor. Install the little Unite's on some stuff for kids. You'll be happier and so will the kids.

If I dump the third motor and use just 2 of the motors and run them off a 36V 25ah lifepo4 battery even thou they are rated for 24v 350watt each, do you think I would have heating issue with just basically a 12v increase?
The 2 motors would be running at all times to share the load. I am using a 12-48v 1000 watt brushed controller.
If I would not have a heating issue would the added speed cause any other issue on the motors sometime in the future?


I realize that using the two motors at 24v the wattage increase up to 700watt and going up a hill and drawing a steady 700watt i don't have any issue with overheating so probably if i can stay within that range or even a little higher with the 36v battery then no overheating would occur right?

What is the max temp you think these motors can handle?

What batteries are you using? More likely your entire problem is crappy batteries.

Simple test, unplug the motors and only plug in 1 at a time and see what speed it runs at. If they are all the same then its your batteries are not powerful enough or your controller is not powerful enough.

Please setup your profile with your location. Local people might be able to help you after just looking at the bike

The battery is not the issue, whenever I run just one motor alone it goes at a slower speed but when both motors are running I get a very big boost, close to 27mph on flat terrain. I have a 24v 25ah lifepo4 battery.

This is a next setup I am thinking about, please give me your views on it.

I want to use just the two motors at all times running off the 24v 25AH lifepo4 but I want to connect a 24ah or a 12ah SLA battery to the same lifepo4 so at the end of the pack it reads 36v but when you check the lifepo4 section you get the 24v. So most times I would be running off the 24v 25ah lifepo4 section.
Please note that the lifepo4 has a BMS install.

So this is what I am thinking. I want to run the bike off the lifepo4 24v 25ah section but when I want a boost in speed I just fire a swtich or a relay and it activates the 36v and the two motors would now spin faster.
Would it cost a issue on the battery pack seeing that I mix the 24v 25ah Lifepo4 with a SLA battery even thou the lifepo4 section has a bms installed?
The 36v would just be use for a short time as a aid to climb hill. The 12v sla will be charge separately with a 12v charger.
Also if I use a 12ah SLA battery instead of a 24ah SLA just to cut down on weight would it be detrimental to the 25ah lifepo4?