What can be done about motor overheating?

CGameProgrammer

CGameProgrammer

10 kW
Joined
Mar 30, 2007
Messages
645
Location
San Diego, CA
I've been running 72V 35A with a Crystalyte 5303 for a little while now, and recently the weather's been 80 degrees and sunny. With this hot weather, my motor gets very hot after 10 miles of fast riding. It was too painful to touch for more than a few seconds after such a ride earlier today, when I pressed my palm against the side cover of the motor. That's really annoying because I want to increase range, though longer trips may increase heat even more, and I wanted to upgrade to 96V eventually.

Exactly how hot can the motor safely get? Is there something wrong with mine, that it should get so hot from 2.5 kW? I know Lowell runs like 8 kW on a similar motor. I'm worried about the glue that holds the Hall sensors melting, or the sensors themselves failing.
 
I'd worry about the magnets being damaged before the other things, although the insulation on the wires might be another weak spot.

Two things I can think of, one is to lower the current limit, which will limit your speed and acceleration (not as much fun).

The other is forced air cooling. Forced-air would be pretty challenging on a hub motor, and I don't know anyone who has actually tried it. I suppose taking the motor apart and drilling a ring of holes around the perimeter of the side cover would help quite a bit. I'd recommend really big holes (1") that are lined up with the windings. You might get enough air through there that you don't need a fan. It would be a good idea to cover the holes with some fine screen or mesh of some sort to keep chunks of debris out.

The space between the spokes inside the motor might be enough to stash a small CPU cooling fan to really move some air, but I'm not sure how you would power the fan; it would need some kind of rectifier/voltage regulator to run off the motor wires.

How's the controller temp after 10min?
 
It's 10 miles, not 10 minutes. It was probably 15 minutes of non-stop 38-42 mph riding. The controller I've been able to keep cool by opening up the case ends. I allow air to enter the bottom of the controller from the front and to exit the top from the back. It made a big difference compared to keeping it sealed, which isn't surprising -- anyone who's built a computer knows you don't want to keep the hot air loitering about, and keeping the controller sealed would do just that.
 
CGameProgrammer said:
I've been running 72V 35A with a Crystalyte 5303 for a little while now, and recently the weather's been 80 degrees and sunny. With this hot weather, my motor gets very hot after 10 miles of fast riding. It was too painful to touch for more than a few seconds after such a ride earlier today, when I pressed my palm against the side cover of the motor. That's really annoying because I want to increase range, though longer trips may increase heat even more, and I wanted to upgrade to 96V eventually.
Click to expand...

Something's not right. I've run my 5304 hard for more than 10 miles at over 72 volts and 35 amps on hot days and never even had it warm to the touch. Lowell runs twice that power and hasn't reported any overheating problems either. According to Justin at ebikes.ca, the x5 is supposed to be good for 3-5kw continuous.
 
I have a pile of spare motor covers to play with at the moment and was toying with the idea of drilling holes at an angle to form scoops, kind of like the holes on a cheese grader, My norco will soon be switching from a 406/409 to a 408/4012 on lithium with knobies ( not sure yet on 20 or 16" wheel.. )

How many holes would be safe ?
 
It's not the strongest stuff in the world, but I'd just swag that if the space between the holes is about twice the hole diameter, it still won't be the weakest part of the wheel assembly.
 
Is your hubmotor painted black? I'm wondering if the hot-day overheating couldn't be more external than internal.
 
I tend to agree with xter. I think the heat might be from the sun.

I usually ride the hardest at night, and my motor barely gets warm when the tempature is about 65-70 degrees. But if I ride on a sunny 80 degree day my motor gets hot fast. Since the tempature in the day is only 10 to 20 degrees warmer, you'd expect the motor to be 10-20 degrees warmer too. Right?

But the motor feels pretty hot to the touch to me. I'd guess its 40-50 degrees warmer.

I was having trouble understanding it too.

 
One factor is being overlooked here. On hot days people wear less clothes. I'll bet you guys are lookin at the girls with yer eyes bugged out, mouths hangin open and your tongues hangin out. It's a proven fact that this creates major air resistence and thus much more drag for the motor to overcome.

Simple solution -- button it up, you can still look and yer motor will cool right down.
 
Beagle123 said:
Since the tempature in the day is only 10 to 20 degrees warmer, you'd expect the motor to be 10-20 degrees warmer too. Right?
Click to expand...

Copper gains resistance as temperature increases. At warmer ambient temps, your motor will get warmer, faster.


:(
 
TylerDurden said:
Beagle123 said:
Since the tempature in the day is only 10 to 20 degrees warmer, you'd expect the motor to be 10-20 degrees warmer too. Right?
Click to expand...

Copper gains resistance as temperature increases. At warmer ambient temps, your motor will get warmer, faster.


:(
Click to expand...

Yes but...there's no way an X5 should be getting too hot to touch at 72volts 35amps unless there's something else going on, like direct exterior heating from the sun -- which if this is the case, the inside may not be as hot as it seems.
 
xyster said:
Yes but...there's no way an X5 should be getting too hot to touch at 72volts 35amps unless there's something else going on, like direct exterior heating from the sun -- which if this is the case, the inside may not be as hot as it seems.
Click to expand...

I agree. But I am more inclined to suspect there is some other problem, as you suggested earlier.

I would open the case and see if it is full of debris or cooked windings, etc. Exploratory surgery is called for...


:twisted:
 
I agree with Mr Durden = take it apart. Before doing that make sure the front wheel bearings are rolling well and no brakes are dragging. When inside also check the motor hub bearings to make sure they spin free.

Keep us posted.
 
No, don't take the spokes off. Remove the wheel from the bike then remove the set of screws around the edge of the hub inorder to remove the cover which might be stuck on tight -- gently pry it off. Maybe someone here has a specific method to pry it off. Then you're in.

Again, you don't need to go into the hub if you find a bad wheel bearing (out of four) or a stuck brake -- as these could be the cause of heat too.

Good Luck = keep us posted
 
If a bearing was bad, you could tell just by turning the wheel by hand. I wouldn't recommend taking it apart unless it fails some external test.

Just sitting in the sun, a nice big chunk of metal that's painted black can get mighty hot. No power needed. Other obvious suggestions; check the tire pressure and brakes. See if it is hard to pedal unpowered.

Spit sizzling hot is hot enough to waste the magnets. I think most of the parts should be good for at least 160F.
 
OK, I went for a ride at midnight last night, and the motor was barely warm by the end of it, though the controller was the same temperature it gets during the day. So clearly the sun is heating the motor directly and/or increasing resistance.

What can I do about this? It's unacceptable to allow the motor to get so hot just from riding in sunlight. Do you think simply painting over the existing black paint would help? If so, what would you recommend I use?
 
Game, We might be onto something here but I'd do a few more checks to confirm. Are you riding in really hot sun? When the sun is overhead not much hits the hub -- afternoon is different as it's more from the side. Let's just think this through a bit. How bout a run in morning or evening for confirmation.

I'll leave my black Tidalforce and silver clyte in the sun to see the difference -- I have a thermometer.
 
CGameProgrammer said:
OK, I went for a ride at midnight last night, and the motor was barely warm by the end of it, though the controller was the same temperature it gets during the day. So clearly the sun is heating the motor directly and/or increasing resistance.

What can I do about this? It's unacceptable to allow the motor to get so hot just from riding in sunlight. Do you think simply painting over the existing black paint would help? If so, what would you recommend I use?
Click to expand...

Paint that clyte white! Or at least silver....I'm interested to see Nimbuzz's test results. The color should make a huge difference in direct sunlight.
 
I set the Crystalyte 5304 and the Tidalforce M750X out in the sun together. It was a full-sun bright day the entire time. Hubs were slanted generally at the sun at the same angle. Ambient air 80 F, slight breeze. There was also a dark grey Volvo nearby.
After one hour at 12:30pm
C-Lyte 96F
TF 107F
Volvo Roof 153

Two hours later
C-Lyte 99
TF 124
Volvo 153

I took a number of readings each time with an infared thermometer that seems accurate. The C-Lyte has a very bright metal flake sliver paint.

My conclusion; ebikes would not usually be aimed up at the sun for three hours. I don't think the temp difference explains Game's overheating.

I think he should do further testing at different times of day befor painting or taking apart the motor. If he is riding in extreme hot, direct sun -- maybe color matters. I'd put in a call to the dealer asking if other black hubs get hot.

Further investigation and the often mentioned but not replied to (that I noticed) bearing and brake check
 

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There are no rear brakes and I doubt bearings are the issue because, as I mentioned, I rode it at night recently and the motor remained cool. So it must be heat-related, but I need to do something to try to prevent it from getting so hot. My rides are not long and I'm "only" using 2520 peak watts.
 
That's a ;ot of watts in my book -- couldn't that be the whole heat problem?
When you ride at night Game make sure you are using the same amount of power.
 
Nimbuzz said:
That's a ;ot of watts in my book -- couldn't that be the whole heat problem?
When you ride at night Game make sure you are using the same amount of power.
Click to expand...

It's not the problem for others here with the same motor. I run the same wattage. Lowell runs twice that. No overheating issues at all. Mine doesn't even get very warm running it hard up hills at 2,500 watts.
 
Right, and my hub motor is painted black, like all X5 motors purchased through ElectricRider, but Lowell's and xyster's are silver, so it's possible the paint is the issue. Anyway I went and bought white spray-paint which I'll probably spray on sometime in the next few days and see what a difference it makes, if any.
 
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