Battery temp of 15°F now appears to be where Rivian stops aggressively heating the battery

[Dark-Fx]

It's also the threshold for completely disallowing regenerative braking. Last winter it seems like Rivian would always aggressively heat a cold battery until it reached 50F, unless you had regen braking assist turned on (I don't typically use it, so I don't have the historical data of when/if they'd be as aggressive at heating)

Got into my R1T this morning, which has been unplugged and sitting outside for several days. Over night low was 10F, battery temp had dropped down to 14F.
I did not do any sort of preconditioning at all before leaving.

I didn't manage to capture the transition from aggressively heating to what seemed like it could have just been passive heat, but I did observe it. A short time after the battery hit 15F, the front motor temps were into the mid 100Fs and the rears were climbing past 100, before starting to fall back down.

By the time I was 3.5 miles from home, the truck had already used 6% of the battery, and the cabin overall was still fairly cold. I had defrost on HI for this whole period. You can see where the 15min efficiency curve started to head back up over 1 mi/kWh, and that correlates with the period where the truck stopped being aggressive with motor/battery heating.

15 Minutes into my drive, the battery was now at 19F.

After arriving at work after 32 minutes, it was at 22F. Regen was still severely restricted. The last part of my commute is mostly downhill, and on slower roads, so that's the reason my efficiency kept going up to the end. I used 17% of the battery for my 18.5 mile commute.

Next week we're supposed to have below zero overnight lows, so I'm planning on repeating this experiment then.

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[egar]

Very interesting observation. I’m looking forward to your updates!

 

[Nixapatfan]

Nice, was wondering where that point was as I've seen mine hit as low as 17 so far and didn't see it trying to heat the motors/batteries at all. Also I noticed the biggest efficiency drop seems to occur after hitting battery temp somewhere in the mid 20's, when it is warmer I'm able to hit 2m/kwh under that it's almost impossible to get that graph in the green.

 

[Riviot]

Thanks for your contributions! Stick it back in the freezer, report back more findings.

 

[sherold]

That battery temp threshold jives with the info from this article...
https://stories.rivian.com/cold-weather-testing

 

[zefram47]

Interesting. If it's going to be that inefficient anyway, curious they're not just being as aggressive as before to get the battery warmed up. Maybe the thought is that from fleet data they've noticed relatively short trips and heating the battery doesn't make sense when the truck is just going to sit and cool off again at the office for most of the day then be an ice cube again on the way home. If they've deemed the battery safe to use at 15F then there'd be no strong reason to heat it as aggressively. The biggest ugly for me is not having regen, but I don't care to use the regen "assist" as I'd rather just use the brake pedal...but that was when regen wasn't severely limited or non-existent for most of the drive because of the aggressive warming.

 

[1stPlace]

I think last Winter my R1S battery only heated to ~50degF when pre-conditioned. It would certainly be a big waste and drain of energy otherwise to keep it at that continuously.

There really needs to be a way to ensure the battery is heated for maximum range when leaving for longer trips. Hopefully they implement a manual pre-condition button in the app and allow it to be done while plugged into a level 2 charger at home as well, so that we can actually get maximum possible range.

 

[beaker]

Is there a best practice to tell the truck to pre-warm the battery drawing from the charger?

 

[emoore]

14F makes perfect sense since it's -10C and that's what we keep our minimum batteries for satellites at. They are similar chemistry as most EV batteries.

 

[Dark-Fx]

That battery temp threshold jives with the info from this article...
https://stories.rivian.com/cold-weather-testing

They definitely are not warming until "full performance" as stated in the article, though. It did used to be closer to that originally versus what I observed today.

Interesting. If it's going to be that inefficient anyway, curious they're not just being as aggressive as before to get the battery warmed up. Maybe the thought is that from fleet data they've noticed relatively short trips and heating the battery doesn't make sense when the truck is just going to sit and cool off again at the office for most of the day then be an ice cube again on the way home. If they've deemed the battery safe to use at 15F then there'd be no strong reason to heat it as aggressively. The biggest ugly for me is not having regen, but I don't care to use the regen "assist" as I'd rather just use the brake pedal...but that was when regen wasn't severely limited or non-existent for most of the drive because of the aggressive warming.

I suspect that's why the behavior seems to have changed a little. I imagine this change is at least partially responsible for the improvement in cold weather EPA range when they tested gen2 as well.

At least it's still possible to force it into heating by navigating to a nearby DC charger.

 

[supernu8]

This is interesting, and explains why I haven't seen the motors doing their heating cycle in my truck so far this year.

At least it's still possible to force it into heating by navigating to a nearby DC charger.

Any chance you could switch into sport mode during one of your experiments to see if the temperature regulation kicks in to a higher level?

 

[1stPlace]

At least it's still possible to force it into heating by navigating to a nearby DC charger.

I do not believe it is helpful to pre-heat for range unless the energy is coming from your level 2 charger, and navigation does not appear to pre-condition the battery if you are still plugged in--I just checked. If you are not getting more energy from the wall, then you are better off just driving to heat the battery.

So I think the question of how to pre-heat for more range is still unsolved at this time.

 

[HyperionMark]

Great info, thanks!

I too am curious how different modes might affect the temp threshold.

 

[Jonger1150]

Even a 110V extension cord is a massive step up from nothing. When you run the climate, it will lock the motors and heat the fluid that cycles through the battery.

I see 30F to 65F in like 20 minutes. That 65F slowly ticks down all day, but my Rivian (In Michigan) has never gone below 40F yet this winter.

Use the app ABRP and you can monitor battery temp and every other stat in real time.

 

[Dark-Fx]

I do not believe it is helpful to pre-heat for range unless the energy is coming from your level 2 charger, and navigation does not appear to pre-condition the battery if you are still plugged in--I just checked. If you are not getting more energy from the wall, then you are better off just driving to heat the battery.

So I think the question of how to pre-heat for more range is still unsolved at this time.

Oh, for sure it's disadvantageous for range to heat the pack from energy in the battery. I'd typically rather have full regen/power than the extra range on a day-to-day basis. I know others don't like seeing the efficiency so poor for so long, and if you actually need the range, it definitely sucks to watch the range drop from pack heating.

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