Is preconditioning before DCFC really worth it?

[smashweights]

So I took my '22 R1T LE out to try to DCFC for the first time locally. We're going on a trip this weekend and I just wanted to see how it worked and ensure that it did. Drove about 5 miles from my house to a Supercharger. The truck was preconditioning and clearly cooking extra electrons as I was getting about 0.9mi/kwh on a drive I would normally get about 2.3mi/kwh and burned off about 5% battery in 5 miles. Battery started at 50F and on arrival was... 51F. Ambient temp was mid-30F.

I only charged for about 5 minutes but it worked flawlessly, plug and play and auto charged my Rivian account with an EV Supply Co NACS to CCS1 adapter. Put 10kwh in, basically what I used driving there at $0.59/kwh. So in ten minutes I used nearly 5kwh to add 1 degree to the battery.

It got me thinking, preconditioning essentially used nearly $5 worth of electricity (more like $2.50 since my efficiency was halved). I can't imagine being on a road trip and it preconditioning for an hour and using up $15+ in energy just to warm the battery, especially since it was almost a negligible amount. The 5 min DCFC session heated the battery from 51 to 61 degrees in 5 minutes while charging at 124kw.

I guess the point of this ramble is why bother preconditioning? It uses a large amount of energy and the fast charging itself will heat the battery up much faster anyway? Since you're paying per kwh at the DCFC you're spending a lot to save maybe a few extra minutes waiting for the battery to have a more optimal charge curve essentially? Does the preconditioning efficiency improve over the longer it runs? Extrapolating my experience, it could take nearly 50kwh to get a 10 degree gain in battery temp, which would cost nearly $25 in DCFC charges...

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[iamnid]

Your test was a short drive where plenty of energy was probably bringing the battery up to temperature in the first place. On a road trip preconditioning won't be sick a significant hit and the charging speeds are well worth it

 

[smashweights]

Your test was a short drive where plenty of energy was probably bringing the battery up to temperature in the first place. On a road trip preconditioning won't be sick a significant hit and the charging speeds are well worth it

Hopefully. Battery was 50 degrees pulling out of the garage so there wasn't much bringing it up to temp getting done. Definitely saw the motors temps cranking up to about 160-170 so I'm hoping once they're up to whatever preconditioning temp Rivian targets the energy usage drops considerably.

 

[JacobAZ]

The primary point of preconditioning it to get charged faster, not necessarily use less energy ... but there are a number of relevant variables, battery, motor and outdoor temperatures. My experience is the battery likes to precondition to about 105 degrees in cold weather. But charging speed is about the same in a window from around 90 - 115. The colder the motors, battery, and outdoor temp, the longer it will take to precondition and more Energy. Yes, you can skip precondition and charge a 50 degree battery, it just takes longer. Does preconditioning use more or less energy than not preconditioning? My guess, is preconditioning probably uses less energy if the motor(s) have extra heat (usually do), since it is transferring waste heat verses the fast charger generating all new heat. Remember preconditioning will also cool the battery if needed.

 

[ndmiller]

Yes 100% worth it.

 

[josh0]

It’s definitely worth it, in the right conditions. We usually spend the winter in New Mexico, where we have a home charger, but this winter were in Baltimore where we don’t, and it was a ridiculously uncharacteristically cold winter. I rarely saw my battery temperature get above 20°, even with preconditioning, due to the short distances I have to drive here. As a result, charging was absolutely nightmare. I was getting 10 kW at 350+ kW chargers. Fortunately, since I didn’t have much driving to do it want that big a deal, but it was a struggle to get my SoC above 30% with the time available and no charging at home.

Getting your battery up to temperature absolutely makes a huge difference.

 

[Time2Roll]

Battery at 50F I would not worry too much about it. Cold soaked close to 30F or below then yes with preconditioning.
Same with high temperatures. Although Not sure how hot is too hot to start a L3 charge.

Of course in critical conditions I would precondition.

BTW some of that loss of economy I assume was for heating the interior.

 

[smashweights]

It’s definitely worth it, in the right conditions. We usually spend the winter in New Mexico, where we have a home charger, but this winter were in Baltimore where we don’t, and it was a ridiculously uncharacteristically cold winter. I rarely saw my battery temperature get above 20°, even with preconditioning, due to the short distances I have to drive here. As a result, charging was absolutely nightmare. I was getting 10 kW at 350+ kW chargers. Fortunately, since I didn’t have much driving to do it want that big a deal, but it was a struggle to get my SoC above 30% with the time available and no charging at home.

Getting your battery up to temperature absolutely makes a huge difference.

I'm not asking if a warm battery charges faster/better, but rather does preconditioning have a significant enough impact to offset the extra energy use and cost?

Battery at 50F I would not worry too much about it. Cold soaked close to 30F or below then yes with preconditioning.
Same with high temperatures. Although Not sure how hot is too hot to start a L3 charge.

Of course in critical conditions I would precondition.

BTW some of that loss of economy I assume was for heating the interior.

Yes, some of that was heating the cabin but I've driven plenty of short drives all winter in much colder temps and get just under 2mi/kwh with heat, two heated seats, and the heated steering wheel running so still was eating up around a kwh every mile to precondition

 

[Gen(R3)Xer]

So I took my '22 R1T LE out to try to DCFC for the first time locally. We're going on a trip this weekend and I just wanted to see how it worked and ensure that it did. Drove about 5 miles from my house to a Supercharger. The truck was preconditioning and clearly cooking extra electrons as I was getting about 0.9mi/kwh on a drive I would normally get about 2.3mi/kwh and burned off about 5% battery in 5 miles. Battery started at 50F and on arrival was... 51F. Ambient temp was mid-30F.

I only charged for about 5 minutes but it worked flawlessly, plug and play and auto charged my Rivian account with an EV Supply Co NACS to CCS1 adapter. Put 10kwh in, basically what I used driving there at $0.59/kwh. So in ten minutes I used nearly 5kwh to add 1 degree to the battery.

It got me thinking, preconditioning essentially used nearly $5 worth of electricity (more like $2.50 since my efficiency was halved). I can't imagine being on a road trip and it preconditioning for an hour and using up $15+ in energy just to warm the battery, especially since it was almost a negligible amount. The 5 min DCFC session heated the battery from 51 to 61 degrees in 5 minutes while charging at 124kw.

I guess the point of this ramble is why bother preconditioning? It uses a large amount of energy and the fast charging itself will heat the battery up much faster anyway? Since you're paying per kwh at the DCFC you're spending a lot to save maybe a few extra minutes waiting for the battery to have a more optimal charge curve essentially? Does the preconditioning efficiency improve over the longer it runs? Extrapolating my experience, it could take nearly 50kwh to get a 10 degree gain in battery temp, which would cost nearly $25 in DCFC charges...

It’s more about reducing the time you need to charge than saving electrons, which varies a lot depending on the temp, how fast you’re going, etc. Usually I find I have to precondition for 30 minutes if it’s really cold out.

If you don’t precondition then it’s going to do it anyway when you get to the charger and take longer to charge as a result.

 

[Johnster]

It seems to me the answer to your question is that with preconditioning you will pay (a bit?) more to charge more quickly, so the choice is entirely yours - cheaper or quicker?

 

[sdemeester]

Drove to MI ski resort yesterday, outside temp 19, 125 mile drive. Selected an EA supercharger about 30 min before getting there, watched motor temps, running around 100 jump up to Orange in 200 degree range, seeme it would alternate front, back and left right a bit to not get too hot while preconditioning the battery. Made almost no difference in battery temp and worse when I plugged into 350 Kw charger it said speed limited by the charger and I never got over about 125-135 Kw. So seemed pretty pointless, and I have to assume that heating the motors up like that hurt range, although I didn’t specifically calculate that. I also wonder about preconditioning

 

[Dark-Fx]

You can't look at the immediate battery temperature to know how much effect it's going to have if you only gave it 5 minutes. It takes longer to get the motors up to temperature, and then the energy consumption levels off but the temperature increase in the battery stays more rapid.

Without preconditioning, you're still losing most of that energy towards heating once you plug in. But now you're also costing yourself more time as well. If the battery is legitimately cold, it's a significant amount of time lost. This session was 10kWh added in 24 minutes. We made another stop a bit after this that was on a 50kW charger that put 16 kWh in 23 minutes, and that was because it topped the charger out after continuing to heat the pack.

 

[iamnid]

when I plugged into 350 Kw charger it said speed limited by the charger and I never got over about 125-135 Kw. So seemed pretty pointless, and I have to assume that heating the motors up like that hurt range, although I didn’t specifically calculate that. I also wonder about preconditioning

If it was limited by the charger, there was something going on with the charger that caused a poor charging session - nothing to do with preconditioning

 

[Meltdwn]

I can’t speak to pre-conditioning from a cold temp, nor about energy savings, so this may not be relevant to you. When traveling in warmer weather, however, there is a huge savings of time when DCFCing by cooling the battery prior to charging. When on a road trip, I don’t want to extend charging stops more than necessary.

 

[Billyk24]

To what battery temperature does the Rivian heat to during pre conditioning?

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