Small Hub Motor Cooling Fiido

I've got a Fiido Q1S and it's got a small, but wants to be mighty, DD hub motor on it that I just can't seem to keep cool.



(Motor specs, as best I can find: site1, site2)

I have added statorade to the motor, it comes with vents I've left open, and I even drilled holes in the other plate -- yet I can't seem to keep this bad boy cool if I so much as even look at a hill.



I had to add a temp sensor (so annoying):



and I took time to validate that the temp readings coming back are good using a different temp sensor. It's within a few degrees, so all good.

I've got this hooked up to a Trampa 100/250 VESC with it set for up to 150 phase amps and a thermal cut off at 100C. When I push it, I find that it can only maintain a motor temp of 100C with 50-70A. That's mostly bench testing, though, with foc_openloop -- but even in the real it's very easy to hit the 100C mark just climbing slight grades. Worse, even riding flat lands I seem to be hovering around the 80C mark.

I've tried this on a 52v system and swapped into a 72v battery and gotten much the same results.

I'm a bit ruffled that I can't seem to get this to perform better and shed the heat more aggressively. Open to suggestions!

chuyskywalker said:

I have added statorade to the motor, it comes with vents I've left open, and I even drilled holes in the other plate -- yet I can't seem to keep this bad boy cool if I so much as even look at a hill.

I had to add a temp sensor (so annoying):

Click to expand...

Where is the sensor located? I couldn't tell for sure in the image.

If you're measuring the windings themselves, then that's probably the most critical point, since the heat most rapidly and other than the hall sensors are probably the most easily damaged by overheating.

I've got this hooked up to a Trampa 100/250 VESC with it set for up to 150 phase amps and a thermal cut off at 100C. When I push it, I find that it can only maintain a motor temp of 100C with 50-70A. That's mostly bench testing, though, with foc_openloop -- but even in the real it's very easy to hit the 100C mark just climbing slight grades. Worse, even riding flat lands I seem to be hovering around the 80C mark.

Click to expand...

That's pretty hot. How fast are you going?

With my heavy unaerodynamic SB Cruiser cargo trike cruising at 20MPH, the rightside motor (a "500w"-ish rated Ultramotor) can reach 60C easy over a relatively short commute with a lot of stops and starts, running it at bursts of about 2kw and around it's rated power continuously. The leftside motor is a "3000w" MXUS 45H, and it reaches similar temperatures with similar power usage; both are in wheels about 21-22" tire diameter. They stay cooler if I am on longer rides with few stops/starts. Both of them use sensors I glued under the windings, where they loop away from the stator just a little to fit it under there.



There are a number of threads that discuss cooling modifications with some specificity and test results that might be helpful. John in CR has some pics and posts about adding internal circulation fins in some compact scooter motors that might be similar to yours in construction.

Cowardlyduck has a thread (something like "cooling fans in hubmotors"?) about a larger diameter motor (9C type) that he added internal fans to pull air thru the stator support; there are pics of it there and in various threads, probably including Justin_LE's big thread about "definitive testing of heating and cooling of hubmotors".

Unfortunately all of his media is gone AFAIK, but LOWRACER had a trike he built a forced-air "shell" against the side of his motor to use a powered fan outside the motor to force air thru the motor sidecover. There are still descriptions in his threads that might be useful.

amberwolf said:

Where is the sensor located? I couldn't tell for sure in the image.

Click to expand...

It's under the gray epoxy on the right of the image, tucked under a bundle of overlapping windings.

amberwolf said:

I've got this hooked up to a Trampa 100/250 VESC with it set for up to 150 phase amps and a thermal cut off at 100C. When I push it, I find that it can only maintain a motor temp of 100C with 50-70A. That's mostly bench testing, though, with foc_openloop -- but even in the real it's very easy to hit the 100C mark just climbing slight grades. Worse, even riding flat lands I seem to be hovering around the 80C mark.

Click to expand...

That's pretty hot. How fast are you going?

Click to expand...

Not much. 10-20mph. Here's a picture from the metr app I was running:



And the grade, according to ridewithgps:

amberwolf said:

There are a number of threads that discuss cooling modifications with some specificity and test results that might be helpful. John in CR has some pics and posts about adding internal circulation fins in some compact scooter motors that might be similar to yours in construction.

Cowardlyduck has a thread (something like "cooling fans in hubmotors"?) about a larger diameter motor (9C type) that he added internal fans to pull air thru the stator support; there are pics of it there and in various threads, probably including Justin_LE's big thread about "definitive testing of heating and cooling of hubmotors".

Unfortunately all of his media is gone AFAIK, but LOWRACER had a trike he built a forced-air "shell" against the side of his motor to use a powered fan outside the motor to force air thru the motor sidecover. There are still descriptions in his threads that might be useful.

Click to expand...

I've caught some of that, but these are really tiny motors by comparison. Just about 4" in diameter; there's little to no real room inside them for any kind of cooling apparatus. The other suggestions are...interesting, but I'm not sure really practical.

The motor is an upgrade for the scooter; and I was using the original motor as a front wheel unpowered. (It was the only thing that fit the wider dropout on a new fork. Geared hub motor, freewheel so not a big deal). I decided to why-the-heck-not it and wired the front motor up with a paired controller. Totally conquered the hill; pushing 20mph is quite a few sections. I'm....stunned at how big a difference it made. The rear motor never went over 70C this time and kept pushing all the way up. I think I was even being a bit stunted by the controllers as I was in the sub 10% battery power remaining band and was getting power lowering going on. (The rear was only getting 50 phase amps instead of 100 I'd had it set to as a max.)

I'm kinda leaning towards the idea that the only real solution is a second motor, especially after that showing.

chuyskywalker said:

It's under the gray epoxy on the right of the image, tucked under a bundle of overlapping windings.

Click to expand...

That's usually the best place for it.

Not much. 10-20mph. Here's a picture from the metr app I was running:

Click to expand...

Maybe it's the acceleration rather than the speed itself. 92Wh/mile is very high for those speeds. Even my SB Cruiser trike, which is several hundred pounds, doesn't take nearly that much--it's usually in the 60s for my worst-case commute, accelerating as hard as I can, about 4kw for a few seconds up to 20mph from a stop.

I'm not climbing any slopes, especially ones as steep as what you're dealing with, though. Do you have any ride data for completely flat areas (if there are any)? Might be helpful as a comparison for troubleshooting.


It kinda sounds like a misconfigured controller/motor combination. Is the controller programmable, requiring setup to the specific motor (like FOC controllers need)? Or is it just a typical sine or trap controller that just needs the right phase/hall combination?

A misconfiguration often results in high no-load power usage, too: if you read low current (couple of amps or less) with the wheel offground, full throttle, then its' probably not that.

I've caught some of that, but these are really tiny motors by comparison. Just about 4" in diameter; there's little to no real room inside them for any kind of cooling apparatus. The other suggestions are...interesting, but I'm not sure really practical.

Click to expand...

They may not be, but you've already done the easy ones.

The only one left that would be easy I can think of would require sealing up the motor and filling it with "oil" (the Justin_LE thread has data on which ones may work better, and how much). Don't know how well it would work for you; if it would be any better than what you're already doing.

The motor is an upgrade for the scooter; and I was using the original motor as a front wheel unpowered. (It was the only thing that fit the wider dropout on a new fork. Geared hub motor, freewheel so not a big deal). I decided to why-the-heck-not it and wired the front motor up with a paired controller. Totally conquered the hill; pushing 20mph is quite a few sections. I'm....stunned at how big a difference it made. The rear motor never went over 70C this time and kept pushing all the way up. I think I was even being a bit stunted by the controllers as I was in the sub 10% battery power remaining band and was getting power lowering going on. (The rear was only getting 50 phase amps instead of 100 I'd had it set to as a max.)

I'm kinda leaning towards the idea that the only real solution is a second motor, especially after that showing.

Click to expand...

2WD makes a huge difference in some cases, when a single motor "just isn't big enough" to do the whole job. It's why I went 2WD on the two cargo bike/trike setups I've depended on (well, that and reliability / redundancy).

It also helps in cases where a motor is "enough" but it's just not setup as it should be or not the right winding for the speed or torque it has to create, with a given wheel size or controller amps or battery voltage, etc.

It's a VESC (Trampa 100/250) so self-tuning with FOC. Doesn't get much better than that these days. There are a lot of minuate you can tweak, but I've never had motor detection leave me in such a bad place that further tuning would be night-and-day. Usually just things like "it rattles at 20mph" or "the spin up is a bit noisey, tweak random KPIweirdName param" kind of stuff.

The freespin load is about 3-5A. It's a bit on the higher side, I believe, because I added the statorade which induces a bit of drag.

On flat ground, the average is closer to 37wh/mi, which is pretty normal for the types of things I ride and my weight.

The oil approach likely won't work out; this motor comes with air vents built in. Even "closed" they'd leak oil. This is certainly a fair-weather only PEV

Thanks for the input, regardless. Just making sure I'm not missing anything obvious!

I know that hill. It's pretty steep. Are you able to measure the Kv and phase resistance of the motor?

thepronghorn said:

I know that hill. It's pretty steep.

Click to expand...

That whole area is my DIY crucible.

thepronghorn said:

Are you able to measure the Kv and phase resistance of the motor?

Click to expand...

For Kv, I have 27 written down. I don't know exactly how I got that as it was a while back, but I usually get it by running a tach against a shiny sticker, noting the running voltage, and just doing the math. I would run it again to double check, but the battery needs a charge.

As for phase resistance... I went and put both the multimeters I have in ohms mode and I basically got 0 to 0.3 in every combination. Maybe my meter(s) aren't good enough here. (Or I did it wrong...entirely possible too...)

chuyskywalker said:

For Kv, I have 27 written down.

Click to expand...

Yeah, 2240rpm @ 83v ~ 27 rpm/v

chuyskywalker said:

thepronghorn said:

I know that hill. It's pretty steep.

Click to expand...

That whole area is my DIY crucible.

thepronghorn said:

Are you able to measure the Kv and phase resistance of the motor?

Click to expand...

For Kv, I have 27 written down. I don't know exactly how I got that as it was a while back, but I usually get it by running a tach against a shiny sticker, noting the running voltage, and just doing the math. I would run it again to double check, but the battery needs a charge.

As for phase resistance... I went and put both the multimeters I have in ohms mode and I basically got 0 to 0.3 in every combination. Maybe my meter(s) aren't good enough here. (Or I did it wrong...entirely possible too...)

Click to expand...

Yeah a multimeter isn't going to be able to measure the milliohm phase resistance of your motor. You'd need to do a 4 wire measurement with a current source using a power supply or something like the circuit below.
https://www.instructables.com/Measuring-low-resistance-4-wire-on-the-cheap/

thepronghorn said:

Yeah a multimeter isn't going to be able to measure the milliohm phase resistance of your motor. You'd need to do a 4 wire measurement with a current source using a power supply or something like the circuit below.
https://www.instructables.com/Measuring-low-resistance-4-wire-on-the-cheap/

Click to expand...

That looks a big more complicated than I'd like to take on, but...

https://www.allaboutcircuits.com/textbook/experiments/chpt-3/4-wire-resistance-measurement/

I do have a bench supply and a second meter; seems like I could do it this way.

Seems pretty darn even to me; which I'm going to guess is good.