Steep hill descent motor overheating.

[pbanddi]

I have searched the forums and online and have not found anything specifically like the issue I just had.
While coming down a steep hill (24 degree slope) with a ton of very large rocks, deep ruts, and holes, the front motors instantly started heating up. In a very short time they went to 270 degrees and kept climbing. Both front motors hit 307 degrees, which is in the red zone. I could hear the motor cooling system ramp up but it didn’t drop the temp. When we got off the hill, the motor temps dropped very quickly. I had the truck in off road, the regen system was controlling the descent well, but that’s what caused the motors to get so hot. The motors were at that temp for around a minute or two, but had the hill been much longer, I don’t think they could have handled it. The hill was only about 100 yards and the outside temperature was about 50 degrees.
The questions I have are; have any of you experienced this, and is that temperature damaging?
Thanks!

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[Zoidz]

It's possible that the battery was at it's max regen power limit, so I'm wondering if the additional braking current was intentionally being dissipated as heat in the motor. In industrial applications there is a device called a braking resistor that dissipates this energy.

I don't think Rivian has released enough/any tech info related to motor temps. We do see temps like that during battery preconditioning so we can assume (?) Rivian has designed/engineered for these temperatures.

For reference, industrial electric motors can have operational ratings as high as 350+ F. These motors have high temp electrical insulation, bearings and lubricants. I hope/assume Rivian has done the same.

 

[Rivian Owner]

Last time I checked, my R1T has a brake pedal, and it works! I assume your Rivian has a brake pedal as well????

If my motors were getting into the "red zone" going down a steep hill, I'd consider applying the brakes and slowing down or stopping using the brakes (made for this sort of thing) until the motors cooled off. Were you just seeing if you could exceed the design limits of the motors?

 

[R1Tom]

Based solely on the mention of motors and not motor...I assume you have a G1 QM.

And then based on that you have the longest powertrain warranty that Rivian has offered to date....which is 8 years or 175k miles.

So with that I would assume Rivian has implemented appropriate thermal protection for those motors if they are running at those temps and if not...then Rivian puts new motors in when they fail.

 

[VSG]

Were you in Rock Crawl mode? Perhaps Rivian doesn't have blended braking in that mode and only uses regen without limiting the regen? But that doesn't make much sense, because regen, like charging, is necessarily limited by how much energy you can push into the battery at a given SoC.

 

[edman007]

Electric motors have more than just go and regen. You can do a reverse power, that is apply full power backwards, while going forwards.

Further, electric motor heating is more dependent on motor torque than motor power.

That means, in an electric, you can actually hold the vehicle, stopped, or near stopped, even at a very steep angle, this will consume power while going slowly or not moving at all. It will greatly heat the motors while doing this. I suspect that Rivian does this in the off road modes, it would greatly improve your control by giving you far more available stopping force with one pedal driving, especially at very low speeds.

 

[pbanddi]

Last time I checked, my R1T has a brake pedal, and it works! I assume your Rivian has a brake pedal as well????

If my motors were getting into the "red zone" going down a steep hill, I'd consider applying the brakes and slowing down or stopping using the brakes (made for this sort of thing) until the motors cooled off. Were you just seeing if you could exceed the design limits of the motors?

No s@$t? It has a brake pedal? Wow, I would never have thought about that!

Did apply brakes and still didn’t drop the temp until back on level ground.
How about trying to post something useful instead of some smart a$$ comment. Or you could just go F@&k yourself too. Either way, I’m good.

 

[pbanddi]

Based solely on the mention of motors and not motor...I assume you have a G1 QM.

And then based on that you have the longest powertrain warranty that Rivian has offered to date....which is 8 years or 175k miles.

So with that I would assume Rivian has implemented appropriate thermal protection for those motors if they are running at those temps and if not...then Rivian puts new motors in when they fail.

Yes, Gen 1 quad motor. That was my thought too. I’m not to worried if it does fail, Rivian has done a lot of me already and I’m sure they will take care of it it there was a failure. I’m just curious if people in here have had this issue and if there is any knowledge as to actual data on the motors’ overheating in these situations and what the thermal limit of these motors are. Thanks for the reply!

 

[cohall]

Unless you got warnings on the driver display, I wouldn’t be concerned.

 

[pbanddi]

Were you in Rock Crawl mode? Perhaps Rivian doesn't have blended braking in that mode and only uses regen without limiting the regen? But that doesn't make much sense, because regen, like charging, is necessarily limited by how much energy you can push into the battery at a given SoC.

I have tried rock crawl mode but find it has too much free roll in these deep hole scenarios when mixed with a steep descent. I’m really surprised it even ran the temps up so high with what I was doing. I’ve seen other videos where guys have gone down much steeper hills and never ran those kind of temps. I’ll probably have to talk to Rivian and get there take on this.

 

[pbanddi]

Electric motors have more than just go and regen. You can do a reverse power, that is apply full power backwards, while going forwards.

Further, electric motor heating is more dependent on motor torque than motor power.

That means, in an electric, you can actually hold the vehicle, stopped, or near stopped, even at a very steep angle, this will consume power while going slowly or not moving at all. It will greatly heat the motors while doing this. I suspect that Rivian does this in the off road modes, it would greatly improve your control by giving you far more available stopping force with one pedal driving, especially at very low speeds.

I’ve seen videos on the R1S that show the wheels actually rotating backwards on hill descent. Pretty cool.

 

[sub]

Yes, Gen 1 quad motor. That was my thought too. I’m not to worried if it does fail, Rivian has done a lot of me already and I’m sure they will take care of it it there was a failure. I’m just curious if people in here have had this issue and if there is any knowledge as to actual data on the motors’ overheating in these situations and what the thermal limit of these motors are. Thanks for the reply!

Did you get an actual error message saying that the motors had overheated? Or are you just assuming that 307 is bad?


The little animation on the drive mode page is not an error message. While the owners manual doesn't show exactly what the overheating error looks like, it is clearly going to be text based and will probably say something like pull over immediately.

If there wasn't a popup saying that there was a problem then most likely there wasn't one.

 

[pbanddi]

Did you get an actual error message saying that the motors had overheated? Or are you just assuming that 307 is bad?


The little animation on the drive mode page is not an error message. While the owners manual doesn't show exactly what the overheating error looks like, it is clearly going to be text based and will probably say something like pull over immediately.

If there wasn't a popup saying that there was a problem then most likely there wasn't one.

Great question, no, I was just watching the motor temps. Also where the display shows the motor temps there is also the center display that shows the powertrain and there where two exclamation marks over the inverters that were also lit up in red, but no text based warnings or “Turtle” mode activated.

 

[sub]

Great question, no, I was just watching the motor temps. Also where the display shows the motor temps there is also the center display that shows the powertrain and there where two exclamation marks over the inverters that were also lit up in red, but no text based warnings or “Turtle” mode activated.

I am pretty sure you are reading more into that animation than you should. Red just means hotter than not red.

I'm not defending Rivian or blaming you. It is totally reasonable to assume red=bad. Why show the info if you are not supposed to use it? But that doesn't appear to be their intent. It seems to just be a fun animation to satisfy curiosity.

The vehicle will intentionally put the motors in the red idling in your driveway on a cold morning to thaw the battery. Surely it wouldn't do that if that was damaging the motors.

If there wasn't an actual error pop-up, I would not assume that it was not working as designed.

 

[HaveBlue]

Compared to internal combustion motors, this is not extreme but the Bosch motors never cooled as well as the later Enduro ones. Curious why the rears didn't get hot, or did they also warm up? I've gotten the enduros warm enough to disable Regen while towing down a steep highway descent.

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