Powering a 80amp motor from a 40amp brushless controller

[fabieville]

I am interested in this ebike 6kw geared motor that is listed in the page below:
https://www.cyclone-tw.com/product/29/data/15

What I need to know is if my 40amp brushless controller will be able to power the 6kw geared motor? as I notice the motor rated amp is 80A.

I am planning to drive the motor with either a 36v or 48v 20amp Lithium battery pack so will the 40amp controller be able to power it and suppose my controller auto limit the current to only 40amp will this hinder the motor full potential seeing that its unable to go up to 80amp? Or will the motor draw more than the 40amp under full load which will damage my controller?

If it can power the motor will there be any significant drop in performance especially in regards to torque?

Or will I have to buy a 80amp controller to match with the 6kw geared motor?

 

[amberwolf]

You can run "any" motor on "any" controller that is designed to run that kind of motor (and can use it's position sensors or is sensorless-capable).

Some things to look for:

Is the motor looking for 80 *phase* amps?

Or is it just "rated" to run on an "80 battery amp" controller?


Also, if the motor is designed to run at a specific voltage, running it at a different voltage will result in different RPM, which you can calculate from the difference in voltage and the RPM it would have at the design voltage.



How many amps you need depends on the power you need to do the job you want the bike to do, and the voltage battery you're using.

Thoughts: Let's say that the motor you're using is meant for 72v. Using it with a 36v battery means that to get the full power it's capable of would take twice the current, so using a controller / battery that only supplies half the original current means the motor will produce (less than) 1/4 the power it could have if used at it's "rated" specs.

So, if you put less power into the motor than it's made for, you'll get less power out of it, too. (less current into it means less torque, less voltage means less speed, current x voltage = power).

How much torque the motor produces depends on the phase current the controller provides, and if they don't actually provide a spec for torque per amp (kT) you could derive it from the RPM per volt (kV), and then figure out the phase amps you have available from whatever controller you're going to use.

The gearing you use between the motor and wheel will also change this--if you use 1:1 gearing it is equal, but higher gearing for more speed means less torque, and vice-versa. To determine the gearing you need to use, you take the RPM it will spin at at the voltage you are going to use, and the speed you need to go, and the wheel diameter you are using, and then use one of the various RPM-to-MPH calculators to figure out the ratio required. (or use the formulas for this available online and calculate it directly).



Whether the motor can damage the controller if you are putting enough load on the motor to draw more than the controller can provide depends on the controller design. If it's correctly designed, it will protect itself against this. If not...it depends on how exactly it *is* designed as for what will happen.


Whether the motor can draw more than the controller can provide depends on the load you're putting on it, so....

If you don't already know how much power you need, then you should first completely define the job and all of the worst-case conditions it has to do that job under, including your specific terrain, wind, road conditions, riding style, etc, and then take those to one of the various online calculators or simulators like the ones at ebikes.ca.

There you can use all the info to create guesstimates of the total power you need to do the worst parts of the job (which is how much power the system as a whole must be able to provide, including battery, controller, and motor), and of how much power it uses over time to do various parts of the job (which helps determine how big a battery you need to get the range you want).

If instead you prefer to "go backwards" and just use parts you have plus this motor (why this particular motor?), and just see what it will do for you, that's ok too, but it means you may not get the results you want and you may have to spend more money replacing parts until it does do what you want. (took me a few years of doing that with my stuff till I got what I wanted out of it, or close enough, anyway).

 

[fabieville]

It is rated to Draw up to 80amps at full load. So with this in mind it would be best to use a lithium battery pack that is equipped with cells and BMS that can handle a constant discharge of 80amp or higher?

 

[DanGT86]

The controller is what determines how many amps you are pulling from the pack. So a 40am controller will typically pull a maximum of 40amps from your battery. If you run a 40amp BMS and cells that can handle 40amps you will be fine to run a 40amp controller.

At low speeds your 40 amp controller might send out 80amps to the motor because the voltage will be lower than the battery voltage.
Think of this scenario:

• Pack provides 40amps at 40volts into the controller for a total of 1600watts
• At 1/2 of your top speed the controller sends 80amps at 20volts out to the motor again for a total of 1600watts.

That motor is rated for up to 6000 watts so it will be just fine with your controller. You will not get 6kw from it unless you have a controller and battery providing at least 6kw.

Like Amberwolf mentioned you will want to know if the 80amp rating of this motor is phase/motor current or if the website is suggesting you pair it with an 80amp controller they sell. I think its phase/motor current because pairing it with an 80amp controller at 72v would be about the 6kw they are rating it at. They list an 80amp controller as a package deal with that motor.

Motor phase current is less of an exact science when it comes to ratings because you can get away with a lot if its for short bursts with time to cool down in between.

 

[electric_nz]

That motor is usually paired with a 60-72v controller that draws 80A battery. Which is relatively cheap and well worth it if your battery will handle 80A. Not sure about phase amps. The motor itself is built very ruggedly with steel gears in the planetary gearbox. So at 40A it will probably last forever

 

[E-HP]

I am planning to drive the motor with either a 36v or 48v 20amp Lithium battery pack so will the 40amp controller be able to power it

Can you clarify what you mean by a 36V or 48V 20amp pack? Are you thinking of using a pack capable of delivering 20A, to a controller capable of 40A, to power a motor rated for 80A?

 

[amberwolf]

It is rated to Draw up to 80amps at full load. So with this in mind it would be best to use a lithium battery pack that is equipped with cells and BMS that can handle a constant discharge of 80amp or higher?

80 battery amps, or 80 phase amps?

You still have to determine the other things I discussed to know what current you actually need.

If you don't do that, then you have to experimentally determine what results you will get, after you buy stuff and wire it all up.

Anything we say about it without that info is just a guess.

 

[fabieville]

Can you clarify what you mean by a 36V or 48V 20amp pack? Are you thinking of using a pack capable of delivering 20A, to a controller capable of 40A, to power a motor rated for 80A?

I bought a 48v 30A battery pack which the BMS inside is capable of delivering 60amps constantly. So is it ok to use that with my 40A controller? Also in times of low voltage/low speed and the controller decide to send more than 40amps and maybe send up to 60 or 80amp to the motor will that damage the controller seeing its rated for 40amps constant draw? Also running the motor at a low speed and drawing up to 60-80amp from it will that cause the internal coil to burn?

 

[amberwolf]

If the controller is 40A battery current limit, it can't pull any more than that, if it's actually designed correctly, it will limit operation to stay within that limit.

The current it allows the motor to draw is phase amps, which is not the same as battery amps, and can be significantly higher than the battery amps ever is. How much higher depends on the specific controller design (and/or settings, if it has any), but a typical ratio can be up to 1.5x.


To know what the motor response is to low speed and high current, you'd need to either test it under your conditions with a thermal sensor installed in it's windings, or check with the manufacturer of the motor, if it isn't one that's listed in ebikes.ca's motor simulator as thermally modelled. (meaning, it does show an "overheat in" result when simulating with it).


However....as previously noted, if you really want the system to work like you need it to, you have to do what was stated before: Define your job, define your conditions, and either do the math for what's required or use the available simulators to find the power needed to do that job. Then get parts that can handle that job.

Since we don't have all the data (only you do), we can't tell you what will work or what won't, or what specifically will happen when you do things or use parts a certain way.

Otherwise you're just going to have to buy parts and try them out, and when they don't do what you want or fail, you then replace them with bigger parts and retest, until eventually you have stuff that does do what you want without failing.

Seems kind of a silly way to do it when it's possible to do it the other way.

 

[fabieville]

Can you clarify what you mean by a 36V or 48V 20amp pack? Are you thinking of using a pack capable of delivering 20A, to a controller capable of 40A, to power a motor rated for 80A?

I am going to use a 48v 30amp battery pack which the BMS is rated at 40amps max discharge to power a 36v-72V cyclone motor which has a rated amp of 80A so i am wondering if the motor will work efficiently in giving me good speed and torque at the 48v 40amps???
and no heat build up even on a very steep incline???
Approx. what would be my max mph on a flat terrain?
Below is the specs for the motor:

Top 10 best and Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit world's Fastest electri

www.cyclone-tw.com

 

[E-HP]

I bought a 48v 30A battery pack which the BMS inside is capable of delivering 60amps constantly.

I am going to use a 48v 30amp battery pack which the BMS is rated at 40amps

Your system will kill either pack since it will constantly be pulling more than the 30A the cells themselves can provide. Maybe you can parallel the two packs.

 

[fabieville]

would it be best to use the other cyclone motor which is rated at 45amp?
see webpage below to see the specs

Top 10 best and Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit Fastest electric dirt bikes Motocross Big Boy ebike DIY Motorized kit world's Fastest electri

www.cyclone-tw.com

I had a 36v-72v 3000watt geared cyclone motor rated at 40amps in the past and i was operating it on a 48v 30amp battery pack with a 45A built in BMS and on a average it use to pull around 15-20amps on a flat terrain on full throttle and with the 40amp controller it never past 40amp the most i see it went to was around 35-37amps when climbing very steep hills.

So if i decide to buy the 36-72v 6000watt 80amp rated one and operate it using my 48v 30amp battery with built in 40amp max BMS would my 40amp controller that i have limit the max draw to around 35-40amp and also would i be drawing roughly the same 15-20 amp on a flat terrain at full throttle?

Also would i expect to get the same performance or better than when i was using the smaller 48v 3000watt motor?