The preconditioning myth

[Singletracker]

[QUOTE="ndmiller, post: 709816,
It's not about total energy usage in life or the price of said energy usage as no-one cares about that. It's about maximizing comfort and range driving an EV in the cold weather..
[/QUOTE]

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[jwanderson88]

I did an experiment. I scheduled a 20-mile trip one way. The departure time defaulted to 20 minutes. When I started, the temperature of the battery was 28 and all four motors were 32. In 20 minutes, I went out and there was no change in any of the temperatures at all. The cabin was warm though. The destination was set up on the navigation screen and it was ready to go. My SOC was 73% I think. It's set to 70, but it charges a little extra. Maybe what it boils down to is the Rivian manages the temperature of the battery according to some unknown algorithm that we have no influence over.

 

[Singletracker]

Bingo! This conversation started out about battery preconditioning and driving efficiency. That’s a different subject than where the energy comes from and how much it costs. What just about everybody is concerned with is how far they can drive and how can that be maximized. I don’t think anybody, especially with a home charger, is giving a second thought as to whether it’s costing them a few cents more to heat the battery while plugged in rather than letting it heat itself on the road. The question is what happens when the plug is disconnected. We’re talking about “driving efficiency”, mi/kWh and that starts when the car starts rolling. Is there a small energy loss when the car is plugged in and charging - maybe a little, but that’s not the point. .

 

[DAJA]

I know that a preconditioned HVB is supposed to improve efficiency, but I have to wonder how much it really does. I‘ve tried pre-warming the HVB and I’ve tried it without pre-warming. Honestly, I don’t see a lot of consistent difference. Yesterday, after an 11º night, I went to my R1T, that lives outside. The HVB was sitting at 19º and the motors weren’t much warmer! This should be a recipe for low efficiency, right? I got in the truck and drove for about 40 miles total. It was about 45º out. After 40 miles, the HVB was still at only 38º. Got 2.21 m/kWh efficiency. Go figure. I could do the same drive after pre-warming the battery and, under the same weather conditions, I would be surprised to do any better or even equal that efficiency.

I’ve said it before and I’ll say it again. With this vehicle, I have found inconsistent, unexplainable results to be the name of the game. I’m always looking for patterns that don’t seem to exist ? I must be missing something.
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Edit: Before somebody suggests that this data was acquired while driving downhill, it was not. I was driving around my valley with elevation gains and losses totaling less than 500’. It was a full circle drive, not a one way, drive.

Same impression. 0F the other day, drove 92 miles getting 1.3 miles/kWh in the morning and got 2.1 miles/kWh driving back in the evening. Morning headwind was 15 mph and evening headwind was 12 mph

 

[PhatDaddy]

Bingo! This conversation started out about battery preconditioning and driving efficiency. That’s a different subject than where the energy comes from and how much it costs. What just about everybody is concerned with is how far they can drive and how can that be maximized. I don’t think anybody, especially with a home charger, is giving a second thought as to whether it’s costing them a few cents more to heat the battery while plugged in rather than letting it heat itself on the road. The question is what happens when the plug is disconnected. We’re talking about “driving efficiency”, mi/kWh and that starts when the car starts rolling. Is there a small energy loss when the car is plugged in and charging - maybe a little, but that’s not the point. .

Ok, let me ask a possibility related question/option but that I haven’t seen mentioned. I have a Level 2 charger installed outside my garage. A not untypical use case for me is to park outside on a weekend day and charge to 70-80% using the Level 2. Then during the week do my local running around during the day and at night pull into the garage and connect my Level 1 (Rivian mobile) charger. The level 1 charges all night (we have no time of use billing options) and almost never replenishes back to 70% by the time I am ready to drive again usually the next day. But the Level 1 has typically replenished enough to mostly make up for what I used the previous day. Gradually thru the week my SOC trends down until I again decide to plug back into the Level 2.
So my question is, if your usage patterns were similar to mine, in cold temps would there be an advantage to charging using the Level 1 because it is pretty much ALWAYS still charging when I go to drive again… so would that allow it to serve as a ‘battery warming tender’? Alas, I can’t really check this out… I’m in central Florida and cold for us lately has been in the 50s.

 

[dleepnw]

Its not a myth in the sense that when the battery is at a more ideal temperature it performs more efficiently. When it gets too hot or too cold, it doesn't. That's why battery management systems exist.

That being said, Rivian missed the mark up when it comes to the R1 thermal management. I remember for years they touted how they cold weather tested the battery and vehicles. But in the real world, its thermal management is trash. Its been over 2 years and we still dont have a manual way to precondition the battery.

 

[SeaGeo]

Its not a myth in the sense that when the battery is at a more ideal temperature it performs more efficiently. When it gets too hot or too cold, it doesn't. That's why battery management systems exist.

That being said, Rivian missed the mark up when it comes to the R1 thermal management. I remember for years they touted how they cold weather tested the battery and vehicles. But in the real world, its thermal management is trash. Its been over 2 years and we still dont have a manual way to precondition the battery.

A warm battery is also a source of heat for the cabin.

 

[2kwik4u]

The climate schedule definitely warms the battery. We've been in the negative temps at night the past couple days and with a climate schedule set, I've been leaving the house in the morning with a battery around 50F. Leave the truck sit without the climate schedule and the battery gets much colder.

Same experience here. Truck is in the garage (plugged in) that is hovering around freezing temps. If I use the precondition to warm the cabin, battery is 50deg when I leave. If I don't, battery is closer to 35-40deg. Needs a good 15min head start to do any good.

THEN

I park the truck outside at the office all day. Temps in WNY have been in the mid-low 20's the last few days. When I go to leave, I precondition the cabin, but the truck isn't plugged in. Battery temp has been under 30deg all week when I left the office.

With all that said......I see no appreciable change in efficiency with the battery warm vs cold. Commute is ~25mi on I-90 each way, and I usually exit the Thruway with the efficiency around 1.6-1.7. Just anecdotally, I find the efficiency is more closely tied to motor temps than battery temps. Driving in Snow Mode for 3-4mi until I'm on the interstate will get both motors up into the 65-70deg range, then swapping to All Purpose seems to yield the best results. Landing at the office the rear motor is back down into the 40's and the front has climbed into the 100's.

 

[Rickmc]

I came across an issue a few weeks ago staying out a house away from home. My battery was 84% SOC but I charge to 100% before I travel 3 hours home so I went to top off to 100% at a High speed charger the night before and could not get it charging. It was vacillating between 0mph and 4mph charging rate from the high speed charger. I tried 2 different chargers and they were working fine for my friend's hummer. I actually dropped him off to get his truck when I decided to top mine off. My battery temp was like 14 I think.

I ended up going home and just plugging mobile charger into outlet and got 1mph to get to 95% the next day.

Would have been nice to have a simple button in app or User Interface in truck to say "heat the damn battery, I want to charge somewhere close!" instead of trying to navigate to a charger 1/4 mile away from where I was staying. I've rarely gotten that to kick in unless I'm on a pre planned trip.

 

[GJPoss]

Try setting a destination in your navigation for a charging station that's close enough that the battery will start preconditioning. I'm curious if that would accomplish what you desire. It would be a pain to have to do that each day, but it should work....right?

 

[stormbreaker]

This is my first full winter with the R1T and dammit in New England we're in a deep freeze of lows in single digits in the morning. Yesterday was -2.

I'm realizing that really poor efficiency is just the nature of this vehicle when its this cold. My drive into work is under 10 miles, and between 6 miles of highway and the rest, I get maybe 1.3 miles per kw. My speeds are around 70mph max. I would set the schedule for my commutes and other days I'd go in on a different day without the schedule. No real difference in efficiency.

Last summer, I'd average 2.4 miles per kw, and on some drives, the meter would be peg at the max range depending where I was.

Do I wish it was better? Yes. But my family and I are comfortable in the truck and we take it where ever we need to go.

Someday we'll replace the Mrs ICE with maybe the R2 or R3 which I would assume have much better efficiency. Either way, I'm full in on EV and Rivian. Stormbreaker is a fine vehicle and I'm proud to have in my driveway.

 

[Phatman113]

Ok, hopefully this will provide some validity to what I was saying.
This morning, I had a scheduled preconditioning. It's set to use the wall charger as necessary. It did charge the battery a little but it also warmed up the motors. So it's clearly using the motors to heat the battery like they told us. Yes, there's some passive heating from the charging, but it is actively using the motors for heat as well.
Pic taken just after unplugging before battery temp isn't visible when charging.

 

[RRennie3]

It's winter in the mountains of Utah and it's cold. I would like to be able to precondition, i.e. warm up the main battery, while plugged in before leaving the house so that it gets maximum range. Why not? Maybe when it comes right down to it, it doesn't matter because I'm not going over 50 miles anyway. I've seen lots of discussion and anecdotal stories, but I haven't seen a definitive yes or no answer. Is there one? Can it be done? If it isn't available now, will it be available sometime and when?

I suspect that pre-warming the battery not do much for the range. I started from a garage in Tahoe with the battery probably in the 50s. The GPS indicated I could get home to the Bay Area with lots of battery left. As started driving the lake level was about 32. As I climbed up Donner pass that temperature dropped into the 20s and the battery left at arrival calc dropped significantly. As I came down the mountain there were localized areas where the temp would come back up to about 32 and battery left at arrive came back up. Then the temp would drop and the battery left at arrival would drop. When I got far enough to down the mountain that temp was in the 40s the battery left at arrival was back to the original estimate. In other words the battery got cold during driving and lost range even though it started warm.

 

[Old Kid]

Maybe it's just me, but I get better efficiency once the motors are heated up to 90-100 degrees F on a dual motor, regardless of the battery temp. This takes about 5 miles with the stability reduced to engage both motors at all times, excel and regen. I park outside in the Bay Area, so the battery doesn't get below 38 usually. ?‍

 

[BCondrey]

I precondition all the time in below freezing temperatures, and have the "pull from AC" or whatever checked. It has never, not once, warmed the battery. Battery is always within several degrees of ambient temperature. Gen 1 DM Large.

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