Yikes! Overheating motors.

[Singletracker]

So, headed into town today, roughly 6-7 miles. Driving at a modest pace, not exceeding about 45 mph. As I looked over to my center display, I was shocked to see all motors registering a temperature around 240 degrees. Whoa! That is pretty darn hot for just putting around. In fact, one motor rose to about 270 degrees, at which point the bar graph for that motor turned red. About that time, I had to stop for a red light. This allowed the motors to cool somewhat, but still very hot.

I usually travel with high regen so I decided to reduce the regen to see it that would make any difference. Surprisingly, the motors immediately began cooling down. When they got down to a more normal 130ish degrees, I put the truck back on high regen, just to see what would happen. I drove around for another 10 miles or so and the temps stayed normal. Go figure. Obviously, I notified Rivian and I‘m waiting to hear what tech has to say about this. I‘ll be doing some more testing tomorrow and see what happens. If it were not for the latest system update showing this data, I would never have known that it was happening. Heck, for all I know, this could have been happening regularly. The truck sure seemed to be driving normally, although I was far from pushing it. Has anybody else experienced this behavior?

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[godfodder0901]

So, headed into town today, roughly 6-7 miles. Driving at a modest pace, not exceeding about 45 mph. As I looked over to my center display, I was shocked to see all motors registering a temperature around 240 degrees. Whoa! That is pretty darn hot for just putting around. In fact, one motor rose to about 270 degrees, at which point the bar graph for that motor turned red. About that time, I had to stop for a red light. This allowed the motors to cool somewhat, but still very hot.

I usually travel with high regen so I decided to reduce the regen to see it that would make any difference. Surprisingly, the motors immediately began cooling down. When they got down to a more normal 130ish degrees, I put the truck back on high regen, just to see what would happen. I drove around for another 10 miles or so and the temps stayed normal. Go figure. Obviously, I notified Rivian and I‘m waiting to hear what tech has to say about this. I‘ll be doing some more testing tomorrow and see what happens. If it were not for the latest system update showing this data, I would never have known that it was happening. Heck, for all I know, this could have been happening regularly. The truck sure seemed to be driving normally, although I was far from pushing it. Has anybody else experienced this behavior?

What was the ambient temp? What about the battery? The truck will use the motors/inverters to heat the battery, so this would be pretty normal if it was cold. You'll see this when preconditioning for a DCFC as well.

 

[Singletracker]

It was about 48 degrees out. The battery warmed up to about 50 degrees. Certainly didn’t seem hot. The truck had been sitting out over night and it was in the mid-20’s last night.

 

[W1SE]

IMO: I worry this is why we didn’t have this information before. It’s just fun data. If the motors were too hot and getting hurt they would turn down regen themselves (this happens going downs mountain). And if too much more you would get an actual warning. I think you should not take too much worry in the information part of the drive mode screen if the truck isn’t telling you something is wrong. The truck is smart and will correct issues if they arise.

 

[Dark-Fx]

Rivian is obviously making waste heat in the motors to help warm the battery when below a certain threshold. It explains why the efficiency is garbage for the first 10-15 minutes on the first trip on a cold day. Since they don't have a heat pump and don't have resistive coolant heating, it's the best way to help heat the battery. Once the battery temp gets up to a certain threshold, the motors will go back down to a normal temperature.

 

[Electrified Outdoors]

Rivian is obviously making waste heat in the motors to help warm the battery when below a certain threshold. It explains why the efficiency is garbage for the first 10-15 minutes on the first trip on a cold day. Since they don't have a heat pump and don't have resistive coolant heating, it's the best way to help heat the battery. Once the battery temp gets up to a certain threshold, the motors will go back down to a normal temperature.

This is brilliant IMO. Just like Tesla does... Its a more efficient way to generate the heat then using resistive coolant heating. Not sure aboit Rivian but i know Tesla, if its really cold, uses multiple methods to generate heat for the batteries. What an exciting time in automotive engineering.... its amazing what these guys/gals can do today.

 

[R1Tom]

Rivian is obviously making waste heat in the motors to help warm the battery when below a certain threshold. It explains why the efficiency is garbage for the first 10-15 minutes on the first trip on a cold day. Since they don't have a heat pump and don't have resistive coolant heating, it's the best way to help heat the battery. Once the battery temp gets up to a certain threshold, the motors will go back down to a normal temperature.

How is this accomplished technically? I guess what I mean is how do they get the motor to run hot without producing additional torque to each wheel?

 

[R.I.P.]

How is this accomplished technically? I guess what I mean is how do they get the motor to run hot without producing additional torque to each wheel?

It is accomplished by lowering the voltage to the motors and upping the amperage. The motors become less efficient and produce heat. This is transparent to the driver, power is delivered as needed/requested. You will hear it called "running lossy".

I was unaware of anybody but Tesla doing this. Bodes well that Rivian copied this creative and effective technique.

 

[Zoidz]

How is this accomplished technically? I guess what I mean is how do they get the motor to run hot without producing additional torque to each wheel?

Most likely, they are modfiying the shape of the electrical waveform that is generated in the inverter and applied to the motor, which determines the total power applied. Going from an optimal waveform (i.e. sinusoidal) to a non-optimal waveform (i.e. modified square wave) applies more power that will be lost as heat. It's very complicated and I could not even begin to explain all the variables, but AFAIK this would be the only way to create heat in a PM motor without affecting the speed or torque.

 

[R1Tom]

It is accomplished by lowering the voltage to the motors and upping the amperage. The motors become less efficient and produce heat. This is transparent to the driver, power is delivered as needed/requested. You will hear it called "running lossy".

I was unaware of anybody but Tesla doing this. Bodes well that Rivian copied this creative and effective technique.

Thanks for the explanation!

 

[NineElectrics]

It was about 48 degrees out. The battery warmed up to about 50 degrees. Certainly didn’t seem hot. The truck had been sitting out over night and it was in the mid-20’s last night.

Perhaps this is why Rivian doesn’t offer battery preconditioning while plugged into the wall.

 

[R1Tom]

Most likely, they are modfiying the shape of the electrical waveform that is generated in the inverter and applied to the motor, which determines the total power applied. Going from an optimal waveform (i.e. sinusoidal) to a non-optimal waveform (i.e. modified square wave) applies more power that will be lost as heat. It's very complicated and I could not even begin to explain all the variables, but AFAIK this would be the only way to create heat in a PM motor without affecting the speed or torque.

Thanks too for the explanation! I work with primarily induction motors but also more and more PM motors now. Typically when I get a call about an induction motor overheating it is a low voltage issue. But my PM motors are mostly integral with equipment and the variables are being controlled by integral controllers.

 

[COdogman]

That’s almost hot enough to cook a pizza. Definitely hot enough to keep my driving burritos warm.

 

[Mike2325]

There goes our information, I'm sure there will be enough calls to tech support to make them eliminate the graph.

 

[R.I.P.]

There goes our information, I'm sure there will be enough calls to tech support to make them eliminate the graph.

My fear as well lol.

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