DC Motor Issues. Burning hot

[Lambrosfl]

I just finished my "mini Golf Cart" project.

I bought a 48V 1000W BL1020 brushless motor rated 3000 rpm. I bought it combo with its own controller.

Project facts:
Vehicle Weight: about 300lbs
Passengers Weight: about 300lbs
Axle sprocket: 41T
Motor Sprocket: 10T
Tires/Wheel: 13" total
Chain: 428

During my first test drive, I noticed that the motor and the motor cable got extremely hot...to the point that the protective flex cable tubing melted and smelled like burning. Also I noticed that the performance reduced dramatically about a minute after the initial test drive, meaning when the motor got extremely hot. Also is good to mention that the motor cables and the controller cables are the factory ones, meaning I didn't cut/extend any cables. Also is good to mention that some similar commercial golf carts (ie Cricket sx-3) is using 36V-1000W motor or 36V-800W brushed motor rated 5000rpm with 30:1 gear ratio - 13" tires.

1- Can anyone suggest why my 48V-1000W motor gets burning hot?
2- Also do I need a motor with gear reduction for better torque and performance?
3- Based on the specs mentioned above, can you please recommend what motor I need to buy (brushed/brushless/with gear reduction/ Power(Watt)/36V or 48V)?

Thanking you all in advance,
LL

 

[Functional Artist]

I just finished my "mini Golf Cart" project.

I bought a 48V 1000W BL1020 brushless motor rated 3000 rpm. I bought it combo with its own controller.

Project facts:
Vehicle Weight: about 300lbs
Passengers Weight: about 300lbs
Axle sprocket: 41T
Motor Sprocket: 10T
Tires/Wheel: 13" total
Chain: 428

During my first test drive, I noticed that the motor and the motor cable got extremely hot...to the point that the protective flex cable tubing melted and smelled like burning. Also I noticed that the performance reduced dramatically about a minute after the initial test drive, meaning when the motor got extremely hot. Also is good to mention that the motor cables and the controller cables are the factory ones, meaning I didn't cut/extend any cables. Also is good to mention that some similar commercial golf carts (ie Cricket sx-3) is using 36V-1000W motor or 36V-800W brushed motor rated 5000rpm with 30:1 gear ratio - 13" tires.

1- Can anyone suggest why my 48V-1000W motor gets burning hot?
2- Also do I need a motor with gear reduction for better torque and performance?
3- Based on the specs mentioned above, can you please recommend what motor I need to buy (brushed/brushless/with gear reduction/ Power(Watt)/36V or 48V)?

Thanking you all in advance,
LL

You have a 300lb. cart
...& carrying ~300lbs. of passengers (~600lbs. total)

Also, running a 10T drive sprocket & a 41T driven sprocket for a (4.1:1 ratio)


I'd have say your gear ratio is way off

You probably need something more like a 6:1
...or maybe even 7:1

 

[itsid]

that'd still not cut it I'd say..
the tiny 1kW motors have stall torque of ~3.5Nm
and you need ~ 45 Nm to get the kart moving..

thus a 13:1 gear ratio is much closer to what you need

'sid

 

[Lambrosfl]

Thank you both for your replies.
My motor gets way too hot and I believe it is not load related because i ran it for about a minute without any load and still gets way too hot.
Instead of changing the sprockets, since it is hard to find 428 for my axle, can i use a different motor. If so, what do you suggest? Maybe 1800w? Do I need to research for a motor with gear reduction...and if yes...what specs do you recommend.
Thank you again for the help.
LL

 

[itsid]

Thank you both for your replies.
My motor gets way too hot and I believe it is not load related because i ran it for about a minute without any load and still gets way too hot.

Yes that's to be expected.. and it's still a load issue.
by now the motor now is (or rather it's magnets are)
already fryed!
the problem with high magnetic flux magnets (neodymium)
is that the do not tolerate heat very well... they start cooking off their magnetic flux if heated above 80°C ( ~175F)
once they lost some magnetic flux,
the efficiency of the motor drops significantly,
and as a result more of the electric power is converted to heat,
the motor gets even hotter even quicker and so on and so forth..

And it's quite normal for the motor at one point to even overheat when used w/o any load if it's been mistreated that way before.

And no, there is no way of remagnetising the magnets for us home gamers, you can just throw that motor away (it's likely cheaper to buy a new one than just the magnets)

Now, you have a terribly high load on the motor,
and you need some serious torque to move that weight even on level ground.

since there are very few reliable information on those cheap chinese motor/controller kits available
and I really cannot find any performance datasheet or torque curve;
I could only make assumptions and guesses for those.

I'd rather not.
you bought (I assume) a 150 dollar kit that's now useless (yes the controller will need to be replaced as well.. it's very likely underpowered for whatever motor you get)
say you buy another such set with 1800w for example
(few of them in fact are more like 1300 watts) and spend another 200 bucks on that, to find out it won't do the trick for that kind of load.
and 350 dollars will be wasted for nothing....

I'd say, find a motor that is for sure capable of providing the torque you need.
like the 3kW HPM3000B from goldenmotor (it's unfortunately not cheap.. 288USD)
maybe even it's liquid cooled variant (338 USD)
[goldenmotor.com]

instead of the gm sine controller for 260USD
I'd say you can safely get one from kellycontroller.com
that's capable of delivering a constant 80A.
and peaking no lower than 150A
maybe you find a cheaper alternative (you should)

Yes, sorry.. I know that's a lot of money to be spent,
but I'm not sure any cheap chinese ebay/amazon/whatnot offer
that's claiming to provide a 2400watt motor is actually trustworthy
in terms of motor performance.

You can look out for one but make sure it is provided with a downloadable performance diagram (power curve)
like this:
https://www.goldenmotor.com/hubmotors/hubmotor-imgs/HPM3000-48V3KW Curve.pdf
or that:
https://www.goldenmotor.com/hubmotors/hubmotor-imgs/HPM3000-48V3KW Data.pdf

And you should look for a motor that's providing 11Nm at the very least. at an efficiency rating of 85% or better.
Only such will work reliably with your ratio and weight.
again you need 45Nm to get moving.. with a 4.1:1 ratio that's 11Nm
that goldenmotor is basically spot on already as you can see.

OR you need to change your gear ratio (since it indeed is terrible)
say to 6 or rather 7:1 and then you can maybe get away with a cheaper 1800W motor instead.

'sid

 

[Lambrosfl]

Excellent reply. Thank you.
Now I understand what it needs to be done.
I suspect that the motor that i have was already used...possibly a return since it got hot from just the first time i tried it (w/o load).
It seems that i will have to go with a good quality motor especially since 60T or 70T sprockets are about $60, plus the cost of a 1800w motor...and yet with the possibility that the Chinese motor will not be as described.
I found some (still from amazon) motors that already have gear reduction and fan. As an example:
https://www.amazon.com/BestEquip-Br...ket+for+GoKart+Tricycle&qid=1595689521&sr=8-1

Did you ever try such a motor?
Does the specific one helps in my situation?

Thank you again for your exceptional support.

LL

 

[itsid]

well a geared motor certainly does help 'adjusting' your gear ratio to a more manageable one..
but I cannot confidently tell you to get one..

it's output is limited to 600 rpm due to it's gear reduction
with your additional 4.1:1 ratio

that means the kart is creeping with less than 6mph
which would be nice for a kids toy.. a pain for an adult kart.
(and a kids kart can and should be MUCH lighter than 600 lbs )

1200Watts is just not going to cut it I'm afraid
frankly I assume anything below 2500Watts is just going to be a waste of time
that 600lbs with anywhere near decent speed is just way too much for something like that.
There is very good reason why electric golf carts usually have 5kW or more under their hood

Yes.. yes I would assume the amazon motor might move the kart
(again at 5.some mph max) but it won't be too happy about it.
especially since the torque rating is even less than one for the typical my1020 sized 1kW motor (2.6Nm instead of 3.XNm.. also I see no fan being mentioned)

And that's excluding my doubts about the internal gears
(which I bet are cheap sintered metal and might not hold for too long under that kind of load)
So for a heavy vehicle,
I'd recommend an ungeared motor and a seperate means of gearing
(namely a jackshaft for compount gearing if either the axle sprocket would get too tall or you cannot change that for some reason or another)
that way each and every bit of the transmission is easily replaceable in case it fails.
and easily maintainable so it doesn't as easily
but that can be labelled as "personal preference"...

Talking about sprockets:
JT Sprockets charge 23.50 € for a 428 60T around here..
I wonder how it can be twice as expensive where you are?

swapping to 420 chain (and sprockets) yield hundreds of results
(since #41 sprockets will fit nicely) and you get a 60T for ~20 USD nearly everywhere.

just saying...

Anyways, IDK I doubt you wired the motor up incorrectly, or have a binding chain/axle whatnot..
since while that'd certainly ruin a motor like that,
it'd be something you would likely have spotted on your own, when conducting that unloaded test.
under no load IMHO that 1kW motor should've performed well.. no load, no issue..
just the weight of some wheels to move at a 4.1:1 ratio... certainly doable with less than 250Watts
So indeed maybe it was broken when you got it...
but still even if not.. it wouldn't have had much of a chance moving the kart in the first place.

Care to post a picture of the golf cart?
we loooove pics around here

'sid

 

[Lambrosfl]

Hello and Thanks again for your detailed reply.

Yes, I am afraid that 1200W is too low, even though Cricket SX-3 and RX-5 use 1000w 36V motors, but I have no clue what kind of motors they are using. Also when I was checking their specs, they mention gear reduction. It worths checking their specs:
https://cricketminigolfcarts.com/mini-cricket-golf-cart/electric-golf-cart-models/

I live in South Florida...I am European too and I wished I was back home during this pandemic. Florida is doing way too bad at the moment. So I am shopping online and indeed 60T 428 sprockets are kind of expensive here, unless I buy from Chine that takes about 1+ month to arrive. Also I am afraid that the sprocket diameter will be too big, meaning it will be too close to the ground (due to my tires being too small-13"). Thus, the reason of debating if I should consider a motor with gear reduction.
Indeed my wiring is fine, no doubts about that-I am an EE. Unfortunately I got my existing 1000W motor from ebay, thus no warranty, etc...
Well, my target is to get roughly 13-15mph, since this "mini golf cart" will be used while we go camping with the family (2-3 times per year), so it will be mostly for convenience rather than being used for golfing/fun. So, I don't mind if it doesn't have a great acceleration or great final speed. As long as the motor doesn't get hot and it is kind of reliable, meaning it won't fail after 4-5 uses, then I will be happy.
I will definitely post some pics later today or tomorrow....I would like to get some feedback on my design and implementation
Thanks again and any more ideas/info will be much appreciated.
Kind Regards
LL

 

[itsid]

I am afraid that 1200W is too low, even though Cricket SX-3 and RX-5 use 1000w 36V motors, but I have no clue what kind of motors they are using.

they're using PMDC motors (non brushless)
as can be seen in their wiring diagram
https://cricketminigolfcarts.com/wp.../Cricket_RX5_36VwVoltageRegwSpeed-Control.pdf
(two wires on the motor is a dead giveaway)
those can push a bit more torque than BLDCs

"10 - 13 mph" however I'd highly doubt...

I mean sure.. once that cart is moving and on level paved ground..
with just a single small driver (110lbs or less) it won't need
no power;
150-160 watts perhaps... maybe 300 with a pebble in the way.

but to GET the cart moving does require a decent push.. and that... I doubt the 1kW motor is capable.

Since we just talked about these kinds of motors and misconceptions
about PMDC vs BLDC
I happen to remember the Unite My1020 PMDC in a 48V 1000W configuration happens to be able to push 4.05Nm of torque peak
And with the 45Nm I think I remember you need
that'd need a 11:1 gear ratio to work
(but it won't be happy about it and die if tryed once too often)

and that'd be 11mph.. so just about right
considering their claim of "10 - 13 mph "
on the lower end of things, and not exactly nice to the motor
(one hill and it'll cook it's coils and magnets off really)

"stitched with a hot needle" as we say around here...

Frankly, that alone would lead me to believe those guys are not exactly selling stuff to make their customers happy

Maybe a "Yalu BM1109" if you can find one (1800W BLDC)
it's still very much on the edge but should almost work with a 10:1 gear ratio

and again no.. 4.1:1 ratio is never ever going to cut it (not without a motor that's not providing 10.8Nm )
and if you get a small one that does via internal gearing..
then it again comes at the cost of reduced speed.

'sid


PS I'll recalc, but I don't have high hopes

Okay.. here goes.
here's the math explanation
I use sine of six here since a golf cart has to tackle smooth but uneven terrain quite usually and
sometimes the grassy hills are steeper than your average road .. feel free to adjust.

275kg * 9.81 kgm/s² * sin(6) = 282 N

282N * 6.7 m/s = 1889.4 Watts

So for 606lbs total weight up a 10% inline slope at 15mph you need a motor power of 1890 Watts (mechanical)

and that's in an ideal frictionless setup ...

let's try some compromise values...

270 kg * 9.81kgm/s² * sin(4) = 185 N

185N * 4.5 m/s = 832.5 Watts

better!
that means 595 lbs up a ~7% incline slope at just 10mph and is likely a more reasonable guess for the performance of that cricketcart therefor

Now let's see if we can move closer to your target:
your min targeted speed (13mph)... 5.811 m/s
means for a 1kW motor
we're left with
1000 Watts / 5.811 m/s = 172.1 N

172.1 N for a 600 lbs kart means

172.1 N / ( 272 kg * 9.81kgm/s²) = 0.0645 or sin(3.698)

so with your intended setup you cannot climb any hill with a slope of more than 6.45% (which is an angle of 3.7° roughly)

but let's say that'll do the trick for you

with a 13" wheel and 272kg of weight you need a wheel torque of indeed 44.9 Nm
let's call that 45!

with the just over 4Nm of torque you need a 11.1:1 ratio (elevenoneone!! LOOOL)
unfortunately that motor wouldn't run quick enough to get to 13mph at that ratio
(it'd run ~2900 rpms and reach maybe 10mph up the hill.. ~3400 and 12mph on level ground)

but yeah.. that's about as good as it gets I'm afraid with as little motor power

'sid

 

[Lambrosfl]

Hello Again...and thank you for your detailed reply.

Too busy lately, yet I managed to replace the motor. The company I bought the initial 1000W 48V BL motor replaced it with another 1000W 48V BL motor with 1:5 gear reduction.
Let me start by saying that the new motor does NOT get hot at all. It gets very slightly warm even after 20 minutes on full speed with full load.
The new motor came with a 14 Teeth sprocket. The axle sprocket has 41 Teeth and as I mention above, the gear reduction of the motor is 1:5 and its torque is supposed to be 3.4 N.m (if true) at >80% efficiency (if true). My tires are 13".

Result:
My home made mini golf cart accelerates quite fast. Much more than I expected. Yet, as you very correctly mentioned/calculated above, the final speed is low. I get about 7mph with full load. My target was about 10-13mph.
As an engineer, I always have to have something to do/try, so I am thinking to change the sprockets (preferably the axle sprocket) to improve the final speed. I understand that if I go with 15" tires, I might get about 1mph, which does not help much, but I am not sure If I can get about 3-4mph extra by changing the axle sprocket, without ending up with acceleration issues.
Well these are the latest updates. I attached a pic as well.
Any advise in regards to gaining final speed by changing the sprockets, will be much appreciated.

LL

 

[Lambrosfl]

Hey itsid and all,
Everything seems to be fine with the new 1000W 48V motor with gear reduction. It doesn't get hot at all and runs well.
I changed the sprocket and I get about 9-10mph which is fine for the purpose I want it for.

Since yesterday, I noticed that the motor stalls on acceleration, meaning it stops when I press the pedal fast. I have to press the pedal very slowly to get it going. Once it moves it runs just fine. The batteries are fine and it stalls even when it is fully charged.
Any ideas what might be causing the problem? Faulty pedal maybe, or faulty controller?
Any input will be much appreciated.
Thank you
LL

 

[itsid]

the motor unable to rev up can be due to a bad controller..
what controller are you using? (post pics!)
if it doesn't care about motor feedback for example (like say a cheap home appliance controller)
it commutates faster than the motor is able to react, thus is locking the motor in place
(and that again will certainly heat up the motor.... so don't try forcing it...!)

'sid