Cold Weather Performance

[Riviandog]

The recent Denver media event showcased ideal off-road scenarios, mostly dry and moderate weather. What happens to off-road performance in snowy and or muddy trail conditions? What would idle and active battery drain look like in freezing or subzfreezing ambient temps?

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[Dark-Fx]

The recent Denver media event showcased ideal off-road scenarios, mostly dry and moderate weather. What happens to off-road performance in snowy and or muddy trail conditions? What would idle and active battery drain look like in freezing or subzfreezing ambient temps?

8-10" of snow in my Bolt at 35 mph uses about 1kWh per mile. I imagine that the Rivian would do better because it isn't plowing.

 

[Riviandog]

8-10" of snow in my Bolt at 35 mph uses about 1kWh per mile. I imagine that the Rivian would do better because it isn't plowing.

To be more specific, how is traction control during cold weather offroad performance? I dont recall hearing about any drive modes to deal with slippery, icy, muddy and/or snowy conditions.

 

[ajdelange]

Rolling resistance is the largest load on a BEV until one gets into speed regimes where drag dominates. Ans rolling resistance is not dependent on speed. So if you get into any situation where the tyres have to push anything out of the way (mud, snow, water, sand...) rolling resistance goes way up and range way down. We can estimate the rolling resistance for the R1T on concrete at
0.01*(8500/2.2)*9.8*1603/3600 = 168.598 Wh/mi (out of 440 EPA). That can go up 30 times in sand. Don't know about mud or snow but I think it is obvious that even a doubling of it can have a bif effect. I know that one of the biggest surprises I experienced in BEV driving was consumption of normally 300 Wh/mi jumping to 380 or so in heavy rain.

As for idling in cold weather: The Rivians don't have reversible heat pumps so all heating is going to have to come from the battery. Can't see more than 1 kW (3412 BTU/h) being necessary so 1 kWh/h.

 

[Dark-Fx]

To be more specific, how is traction control during cold weather offroad performance? I dont recall hearing about any drive modes to deal with slippery, icy, muddy and/or snowy conditions.

It might not be necessary to have a specific snow mode. There is some advantage to allowing a little bit of tire spin, it's probably accommodated in the standard off-road mode. On my Bolt I tend to turn off traction control because it's too aggressive at trying to stop tire spin.

 

[ajdelange]

There is some advantage to allowing a little bit of tire spin, it's probably accommodated in the standard off-road mode.

You can say that again. No slip, no thrust. The controller's job (one of its many jobs) is to try to keep wheel spin in the linear part of the thurst/slip curve. To do this obviously it must apply some torque and measure the slip. That's why I think, for example, we see off the ground wheels spinning slowly in the recent videos.

 

[jeepn30]

I know on my Model S a 10-15 mile drive uses almost twice as much energy at about 10 degrees F if the battery hasn't been warmed up. Of course my '13 uses resistive heat. I haven't read what Rivian is going to do heat the truck. The heat pumps on the Model Y and 3 supposedly do much better efficiency wise than my car. I will say my rear wheel drive S performs very solid in winter conditions for the most part, which was somewhat surprising.

 

[crashmtb]

I expect a 30-40% hit in winter
A thread: https://www.rivianforums.com/forum/...eather-driving-thread-tips-tricks-tears.2275/

 

[Riviandog]

It might not be necessary to have a specific snow mode. There is some advantage to allowing a little bit of tire spin, it's probably accommodated in the standard off-road mode. On my Bolt I tend to turn off traction control because it's too aggressive at trying to stop tire spin.

That's probably true, with independent electric motors at each wheel the vehicles ability to adapt is beyond anything weve seen before.

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