Do electric motors "warm up"?

[alvinlwh 5895]

I started taking speed readings recently and noticed something strange. In the first minutes on freshly charged lipos, so voltage should be at its highest, the speed is slower than, say, the speed 5 minutes later.

For example, first minute on a Thunder Dragon with a TZ is 23mph, but it increased to 25 after about 5 minutes. 

Same with a MST TCR-M with a 380 Sports Tuned, 29mph at the first minute and 37mph five minutes later. 

I will expect speed to go down as the battery run down and voltage drops? Not up? I noticed the same with earlier tries, but only really record them today. 

Is this the motor and/or battery warming up or something? 

[MadInventor 3884]

In full size EVs. battery performance is degraded if the battery is very cold.  I know it's cold in Scotland, but that cold ??????

It might be the grease in the roller bearings and on the gears becoming more viscous as it warms up. I remembering owning a car that the used to change gear a lot better once it had been driven for a few minutes.

I would expect the motor to perform better, the colder it is, as conductors work more efficiently the colder they are (Hence why some superconductors have to be kept extremely cold.

[alvinlwh 5895]

17 minutes ago, MadInventor said:

In full size EVs. battery performance is degraded if the battery is very cold.  I know it's cold in Scotland, but that cold ??????

It might be the grease in the roller bearings and on the gears becoming more viscous as it warms up. I remembering owning a car that the used to change gear a lot better once it had been driven for a few minutes.

I would expect the motor to perform better, the colder it is, as conductors work more efficiently the colder they are (Hence why some superconductors have to be kept extremely cold.

It is considered a warm (to us) day today. 😉 Well, the batteries are charged up indoors just before throwing them into the car and taken out to drive, so should be in the 20s range I guess. 

What you said about the grease in the bearings makes sense, but from 29 to 37? That is a 27% increase! Wow! I am surprised that they have that much drag. 

I too expect the motor to perform better when cold, which is why I am investing in fans now. On top of that, what I am running recently are stupidly geared, so they get very hot very quickly. 

[Willy iine 18805]

I could be that the drivetrain loosens up when warmer.. like greases and oils in bearings lose viscosity when they are spun and heated.

 

[M 800STD 586]

Lipo.

Lipos have a higher discharge rate when warm.

 

[alvinlwh 5895]

12 hours ago, Willy iine said:

I could be that the drivetrain loosens up when warmer.. like greases and oils in bearings lose viscosity when they are spun and heated.

 

For the TCR-M, there is not much of a drivetrain to speak of as it is a direct drive 2WD. There are more gears etc on the TD. Is that why there was such a massive gain on one compared to the other? 

[Willy iine 18805]

Are you on brushed motor that have not been cut?   If so the comm could clean up a little and make better contact once the crud cleans off the comm and brushes.   Not sure.  Keep us posted on your findings.   

[alvinlwh 5895]

3 hours ago, Willy iine said:

Are you on brushed motor that have not been cut?   If so the comm could clean up a little and make better contact once the crud cleans off the comm and brushes.   Not sure.  Keep us posted on your findings.   

380 Sports Tuned, sealed can, so no cutting possible. 

[Willy iine 18805]

6 hours ago, alvinlwh said:

380 Sports Tuned, sealed can, so no cutting possible. 

Yeah, especially in that case, I think the comm is just cleaning itself off of oxidation and you get better contact as you drive.

[El Gecko 1344]

13 hours ago, Willy iine said:

Yeah, especially in that case, I think the comm is just cleaning itself off of oxidation and you get better contact as you drive.

Agreed, this happens with my old sealed can Mabuchi 540s as well. Just needs a couple good revs at the beginning to clean out the gunk before going driving.

[alvinlwh 5895]

On 3/19/2022 at 1:31 PM, Willy iine said:

Keep us posted on your findings.

Tested again today. 

380 Sports Tuned 

1st try - 45.5mph (I have doubts about this so reset the GPS and tried again) 

2nd try - 31.6mph (this is around 4mph higher than last week's run) 

3rd try - 28.8mph (this is what the app said it will do, based on 7.4v)

 

17.5T 2200kv (+21 timing) 

1st try - 22mph (around what the app said it will do) 

2nd try - 30mph

So ignoring the first and probably incorrect speed of the brushed, it behaved as expected, speed dropping as battery runs down. The brushless however did see a rather large jump in speed. Both are rather new motors, out on their second or third time today. 

[Willy iine 18805]

Interesting findings, @alvinlwh   Do you use just one GPS meter or multiple meters?  I'd like to know how repeatable the unit can be... maybe even attach 2 speedo's for the sake of testing calibration...(?).    Completely up to you.. 

Do you have a laser thermometer by chance?  

[alvinlwh 5895]

45 minutes ago, Willy iine said:

Interesting findings, @alvinlwh   Do you use just one GPS meter or multiple meters?  I'd like to know how repeatable the unit can be... maybe even attach 2 speedo's for the sake of testing calibration...(?).    Completely up to you.. 

Do you have a laser thermometer by chance?  

Just one. I can, in theory use my smart watch, but I doubt its accuracy. 

I do have a contactless thermometer of some kind, not sure if it is laser or what though. 

One thing is my gearing is quite high, 5.77 for the brushed 380 and 4.71 for the 17.5T, which also has +21 timing, so both motors will be quite hot. 

[Tamiya Fan 1 114]

You said new motor's. Maybe getting better speed as they are breaking in. (loosening up) You are pushing things like you said and will have heat. Is your GPS working right measuring your speed correct? ESC would shut down if there was real problem w/gear or heat.

[alvinlwh 5895]

1 minute ago, Tamiya Fan 1 said:

You said new motor's. Maybe getting better speed as they are breaking in. (loosening up) You are pushing things like you said and will have heat. Is your GPS working right measuring your speed correct? ESC would shut down if there was real problem w/gear or heat.

I had done the water dip run in, 15 minutes each direction with the TX trim so it runs slowly. 

I cannot confirm if the GPS is definitely running right, that is why I reset it after the 44mph reading and tested again which gave a more believable reading. I did notice one thing is all my speed runs (different cars, different motors, different gearing) has higher reading than the app (about 8 - 10% more), so the RPM from Tamiya seems to be lower than in real life. It will be impractical to get a second GPS to check the first and if they disagree, get a third to check which is right? This is a toy car not a passenger plane after all. 

I doubt the ESC will shut down even with me overstressing the motor as I am using a 1060 meant for 540 motors on this 380. The last ridiculously geared project (different car), the silver can melted before the ESC went. 

[Tamiya Fan 1 114]

Sounds like you did everything right! I wouldn't get 2 GPS either. I agree about the ESC, motor would go first with the set up.

[El Gecko 1344]

43 minutes ago, alvinlwh said:

I had done the water dip run in, 15 minutes each direction with the TX trim so it runs slowly.

15... minutes??? Are there any brushes left in there??

I always thought a water break-in should only last 15-30 seconds, a minute at the absolute most. Just until the water starts to slightly turn gray.

[wolfdogstinkus 1893]

Probably irrelevant, but have you ever felt the tyres after a few speed runs?

Tyres warm up, become softer and provide more grip.

I remember checking the tyres on a fast DT-02 and being surprised at how warm they were after a few speed runs.

[alvinlwh 5895]

5 hours ago, El Gecko said:

15... minutes??? Are there any brushes left in there??

I always thought a water break-in should only last 15-30 seconds, a minute at the absolute most. Just until the water starts to slightly turn gray.

It doesn't start turning gray until past 10 minutes. I run it at trim speed, not max speed. Some breaking in guide I had seen said to run for hours, 15 minutes seem short to me. 

[alvinlwh 5895]

1 hour ago, wolfdogstinkus said:

Probably irrelevant, but have you ever felt the tyres after a few speed runs?

Tyres warm up, become softer and provide more grip.

I remember checking the tyres on a fast DT-02 and being surprised at how warm they were after a few speed runs.

Yes, I noticed that too, mainly in the summer, which now is not quite. I will double check again on my next run. One thing that caused me to post this question is the recorded speed is higher after about 5 minutes than the rated speed for the motor. I use an app which take in the KV value which I work out from Tamiya spec and it will work out the expected speed based on gearing and tyres size. It seems like the motor "got faster" if you know what I mean. 

[alvinlwh 5895]

On 3/21/2022 at 8:49 PM, Willy iine said:

Interesting findings, @alvinlwh   Do you use just one GPS meter or multiple meters?  I'd like to know how repeatable the unit can be... maybe even attach 2 speedo's for the sake of testing calibration...(?).    Completely up to you.. 

 

16 hours ago, Tamiya Fan 1 said:

I wouldn't get 2 GPS either.

While I didn't get 2 GPS, I check it against my 1:1 car, which should be reasonably accurate if not I will probably getting speeding tickets or getting rammed up the backside. 

This drive, I did not exceed 30mph and this is the result. I will say the GPS is reasonably accurate as 1:1 speedo are known to read slightly higher than true speed. 

[El Gecko 1344]

13 hours ago, alvinlwh said:

It doesn't start turning gray until past 10 minutes. I run it at trim speed, not max speed. Some breaking in guide I had seen said to run for hours, 15 minutes seem short to me. 

Interesting, your motor must have relatively hard brushes coupled with the slow RPMs, because I've had the water turn gray almost instantly before at 3.0-4.8V.

[alvinlwh 5895]

7 minutes ago, El Gecko said:

Interesting, your motor must have relatively hard brushes coupled with the slow RPMs, because I've had the water turn gray almost instantly before at 3.0-4.8V.

Hang on... Are you breaking in sealed cans or opened (replaceable brushes) motors? I also read that for open cans, the brushes are too soft to break in. 

But back to your original question, yes, this is a sealed can and therefore harder brushes? I most certainly hope there are still brushes in there after breaking in! 😁

NB: I am no expert on this matter, it is just what I had seen during my research. 

[alvinlwh 5895]

On 3/19/2022 at 1:31 PM, Willy iine said:

Are you on brushed motor that have not been cut?   If so the comm could clean up a little and make better contact once the crud cleans off the comm and brushes.   Not sure.  Keep us posted on your findings.   

 

On 3/20/2022 at 1:41 PM, El Gecko said:

Agreed, this happens with my old sealed can Mabuchi 540s as well. Just needs a couple good revs at the beginning to clean out the gunk before going driving.

OK, moving on from brushes, today my brushless recorded 24.0mph after about 10 minutes and then 25.7mph 10 minutes later. Not a huge difference I know, but still seem to go up. Also, I will expect voltage to drop further after a total of 20 minutes run. 🤷

Perhaps the hot tyres theory is true.

[El Gecko 1344]

1 hour ago, alvinlwh said:

Hang on... Are you breaking in sealed cans or opened (replaceable brushes) motors? I also read that for open cans, the brushes are too soft to break in. 

But back to your original question, yes, this is a sealed can and therefore harder brushes? I most certainly hope there are still brushes in there after breaking in! 😁

NB: I am no expert on this matter, it is just what I had seen during my research. 

Open-endbell motors, but I haven't done a water break-in in a loooong time. Like you, I've also read that I should be breaking in open motors dry for 2-3 hours, but I only do it for maybe 30 minutes at the most. I actually don't think I've ever done a break-in on a sealed silvercan, but I think you're right that those brushes are much harder.

I still think there's more going on here than we realize, or possibly a combination of things. Bearings/etc. loosening up, batteries warming up, crud getting blasted off the brushes/comm, tires warming up, all these I think could be factors here. Possibly each one is only very slight, but altogether they have a big effect. Or it could be a kind of feedback loop or chain effect, where one causes another to release.