Brushed vs brushless motor in go-kart setup

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userix   10 mW

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Brushed vs brushless motor in go-kart setup

Post by userix » Apr 13 2021 2:29am

I currently run a me0909 brushed 48v 300A peak motor on my go kart with alltrax 48500 PMDC controller, which is powered by a 13s 44ah lipo pack.

I am thinking about upgrading to the me1507 PMAC motor using the Curtis 1236SE controller and a 72v battery pack.

If given a brushed and brushless motor of similar specs (voltage, amps ,etc), would the brushed motor provide more low-end torque and more aggressive acceleration than the brushless equivalent?

My current me0909 specs48v (300a peak) 14kw peak with 4.8kw continuous. The me1507 motor at 72v hits (450amp) 32kw peak and 13.3kw continuous. Keeping gearing the same, the me1507 setup should allow me to spin out the tires from a dead start? I read somewhere that brushed motors are really good at low-end torque compared to brushless motors. But given the much higher kw ratings of the 72v me1507 powertrain, I should have much more power/torque compared to my existing setup?

While the takeoff/acceleration on current setup is pretty aggressive, I can't spinout the tires. I do like/want very aggressive low-end torque and acceleration and hope by upgrading to the me1507 powertrain at 72v, I can achieve that. I want to peel out when I floor it from a standstill.

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Chalo   100 GW

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Re: Brushed vs brushless motor in go-kart setup

Post by Chalo » Apr 13 2021 2:35am

Try greasing your tires.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

larsb   10 MW

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Re: Brushed vs brushless motor in go-kart setup

Post by larsb » Apr 13 2021 4:29am

A quick check on the spec difference of these motors.. they are not in the same ballpark even. 1507 motor has 4x higher max torque. That’s if you have controller and battery to drive it to the max.

@Chalo: No greasing required :D

markz   100 GW

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Re: Brushed vs brushless motor in go-kart setup

Post by markz » Apr 13 2021 5:25am

Maybe Chalo meant to grease the brushes on the brushed motor for extra torque off the line, old tech and all.

stepus   100 mW

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Re: Brushed vs brushless motor in go-kart setup

Post by stepus » Apr 13 2021 6:32am

brushed motors can have a bigger torque from standstill, they have a comutator to switch "phases" automaticaly - so controller can apply huge DC current, on sensorless motors there is comutation from controller, and it always limits phasecurrent - current that makes standstill torque. So its cheaper to use brushed motor with simple DC controller to have higher standstill torque. But for efficiency its better to use brushless with FOC controller

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Re: Brushed vs brushless motor in go-kart setup

Post by larsb » Apr 13 2021 9:18am

1x vs 4x the torque won’t be offset by the brushed motor starting torque.. 30Nm for the smaller motor is not so much and 120Nm for the larger is a lot..

userix   10 mW

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Re: Brushed vs brushless motor in go-kart setup

Post by userix » Apr 13 2021 8:11pm

Thanks guys. yeah I know the me0909 and me1507 are two different motors all together. I was curious given all things are the same, if brushed motors have higher standstill torque. I guess they do. But if I'm going to the me1507 32kw motor powertrain system, I should be getting noticeably greater torque and power than my me0909 motor, of course given the battery is able to dump 450A. It's using the Curtis 1236SE motor controller. So if the controller is able to dump 450A straight to the me1507, it should have massive torque?
I figure if the kW rating of the me1507 system is more than twice that of my current system, I should experience twice the power/torque?

Generally speaking in terms of torque curves, brushed motors have steeper more aggressive curves compared to brushless?

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Re: Brushed vs brushless motor in go-kart setup

Post by larsb » Apr 14 2021 12:08am

No, they don’t. The controlling and controllers for brushed motors are simpler and therefore can drive full current at zero rpm without trouble - same can be done with a quality brushless controller but it will be more expensive.

A 30Nm max motor is just that, you won’t get 120Nm starting torque just because it’s brushed. What you could get more easily on a brushed motor is 30Nm at zero rpm.

stepus   100 mW

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Re: Brushed vs brushless motor in go-kart setup

Post by stepus » Apr 14 2021 1:56am

Standstill torque is determined by phasecurrent of controler and motor constant - how many amps is needed for Nm. Motor constant is defined by motor construction so its not adjustable, so you can buy only stronger controller to have more torque... Limit is only temperature of motor/battery
here they use brushed motors and it runs as hell :D https://www.youtube.com/watch?v=zI0TNk5gLbU&t=2s
they use L.M.C. 200D135 motor with Alltrax AXE 7245 controller.
info from : http://www.ev-fun.eu/electric-gokart-1/ ... fications/

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Re: Brushed vs brushless motor in go-kart setup

Post by larsb » Apr 14 2021 5:32am

I don't see the point you’re making. Brushed systems can be cheaper, yes. The question the poster has is if they have inherently larger torque. No they don't. That is exactly why a 30Nm max torque motor will never be a 120Nm motor. I've seen gokarts do spinouts on far smaller motors than this (really expensive) lynch motor.

The limit on max torque (valid only for short term since max torque will burn the motor on longer term) for the motor is the saturation of the steel, after it is fully saturated there is very little added torque when current is increased. when a 30Nm max motor is fed more current than it's max it only creates heat.

It is off course assumed that you will feed it enough phase current. Get a powerful controller to fix that one :wink:
Last edited by larsb on Apr 14 2021 11:18am, edited 1 time in total.

Ianhill   10 MW

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Re: Brushed vs brushless motor in go-kart setup

Post by Ianhill » Apr 14 2021 7:08am

Chinnese scooter motors zy1020 48v 1000w brushed motor and its modern 60v 3kw equivalent show that a brushless motor of the same foot print is best.

The brushless uses its internal structure in a more efficient manner more copper more steel and stronger magnets lead to higher output, brushed motor have been good to us over the years and im using one on a scooter build now and screaming it one last time but that will only be at 4krpm max compared to 7.5krpm i got from the brushless version.

And like stated long as theres hall feed back starting torque can be very strong, i see the appeal of dc for how easy and cheap you can get high stall torque but dont be fooled but the sensorless crap.

I got a 60v 45amp controller for £25 old stock in uk and had a 48v 1000w motor for free years ago when i ordered a 36v varient so it dont get much cheaper than that for snap your wrist type of torque to get a brushless setup im looking at £250 all in for cheap stuff so i thought ill make one last heritage ride not to quick but goat like run it 16s and break a few brushed personal bests.

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spinningmagnets   100 GW

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Re: Brushed vs brushless motor in go-kart setup

Post by spinningmagnets » Apr 14 2021 7:32am

Brushed motors have been over-volted about 50% without problems in the past. However, the higher the volts, the farther a spark can jump. Doubling the voltage throws off the timing. That means the phases are energized just a hair too soon and they stay energized just a hair too late.

I suppose you could try narrowing the brushes while upping the voltage, but you may go through a few sets of brushes and even motors before you uncover the peak of over bolted power. Your call.

And now we come to amps. Amps cost real money. If you hot rod a brushed controller, it will get hotter, and the road to ES is littered with burned out brushed controllers and brushed motors.

So you buy a larger and more expensive brushed controller. Then, you fry the motor brushes in a plasma ball. It's happened here too often to count.

My advice is to video you running the brushed motor and controller you have, and sell them for whatever you can get.

The brushless motors are voltage-agnostic, they can take more volts than you are willing to pay for. Let's just say you find a wrecked Zero motorcycle. It uses 28S, 102V

Chances are, any Zero battery after 2013 is fine, and has plenty of life left in it. For $1000 you can get a new cylindrical QS motor and Votol controller that can do 300A peaks @ 72V (20S) = 21,000W

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Re: Brushed vs brushless motor in go-kart setup

Post by Ianhill » Apr 14 2021 8:08am

The zero is a good call its going to be highly capable and will run with your 420 sprocket straight out the gate, the battery may be bit of a pig to fit a go cart its not shaped ideal.

Id go with a custom floor pan make it like an ev the battery is the structure integrity, zero motor on 32s would be quick may need the f1 kart fairings and lie the seat to the floor triple figure time.

userix   10 mW

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Re: Brushed vs brushless motor in go-kart setup

Post by userix » Apr 21 2021 3:03am

https://www.thunderstruck-ev.com/curtis-ipm-system.html

how about this kit geared more for low end 26T motor sprocket to 58T axle sprocket? I should be able to spin some tires?

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Re: Brushed vs brushless motor in go-kart setup

Post by Ianhill » Apr 21 2021 8:20am

I dont think you need to have a crazy high torque figures its light enough to accelarete hard.

A built go kart would have simular mass to a zero bike so that drivetrain geared for the same top speed with your smaller go-kart wheel would have simular performance to the bike for the same input power.

Perhaps its just me been a junk yard dog but the zero looks the way to go and bigger the zero motor the better, gearing is where id be looking at can i get flexible speed range on the wheel size you use with the rpm of an overvolted zero motor if i could that be a no brainer to my mind and wallet.

Its not ginna be as straight forward but thats half the fun accomplishment at the end of having a monster kart check out rich builds quad for an idea of what you can expect speed and power wise, it be a beast.

If zeros where in uk been broken id want one id do what ever it takes to get that into a lightweight dirtbike.

stepus   100 mW

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Re: Brushed vs brushless motor in go-kart setup

Post by stepus » Apr 22 2021 2:31am

carefully choice controller, some are not user programable and have defined power scope / throttle ramp (to prevent lose traction or wheelie), so it will not spin tires instantly as you give pedal to the metal but you will need to brake lock front wheels

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nuxland   100 W

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Re: Brushed vs brushless motor in go-kart setup

Post by nuxland » Apr 26 2021 2:22pm

Here is one run graph when accelerating from standstill with my zero 75-7 motor and sevcon gen 4 size 6 controller.
TimeVSTorque.jpg
TimeVSTorque.jpg (69.07 KiB) Viewed 251 times
And here voltage graph (this is with 10p34s A123 2,5Ah cells pack) and power.
TimeVSVoltage.jpg
TimeVSVoltage.jpg (56.48 KiB) Viewed 251 times
And as tires were hot, they did not spin event with that power and torque :)
We used there 16T in motor and 36T in axel with 428 chain.
https://www.youtube.com/watch?v=2Xp41u1y9KI
Electric kart 60kw: viewtopic.php?f=34&t=68543
100v 35Ah LiPo battery: viewtopic.php?f=14&t=97763
100v 25Ah LiFePo4 battery: viewtopic.php?f=14&t=85912
Scooter battery: viewtopic.php?f=14&t=108227#p1582703

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