The preconditioning myth

[Singletracker]

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 mi/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.

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[emoore]

Some yes's and some no's and lots of guesses. What makes sense is to push a button on the app an hour before you leave and it starts heating up the battery using current from the charger. Scheduling a trip in advance seems like a lot of bother. I like easy. I had a "lowly" Chevy Volt years ago and you could tell it was preconditioning the battery (when it was plugged in) because you could hear it. That's what I like about GM software. It's sensible and has the features people want and need.

It only takes seconds to change the schedule time to an hour from when you want to leave. Hardly a bother.

 

[Dark-Fx]

Any length of drive will benefit from preconditioning if you do it with the schedule while plugged in (scheduling it will allow it to pre-heat the battery pack and not just the cabin). If you just hit the precondition button while the vehicle is unplugged, you're expending more energy than you would otherwise by just getting into the cold vehicle and going.

 

[Nixapatfan]

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.

Same here makes no sense to warm the battery if you aren't planning on draining the battery fully on your trip. Trying to raise efficiency while burning electricity from the wall doesn't make sense if you don't need the full range. Do it because you want a warm cabin.

Warming the cabin plugged in or not does trigger the battery to also warm up, when I trigger it a few minutes before driving I can see the motors at a much higher temperature than when driving.

 

[CompilerBreak]

^^^^ THIS ^^^^

There is no myth, set a leave time with or without the truck plugged in and it will warm both the cabin and the battery by that time....And the motors as that's what warms the battery.

If anything I'd say the myth is around the fact that either way you'll use nearly the same amount of electricity, it just only makes a difference if you care whether that's coming from your house (which may have a time of use billing where it isn't advantageous) or from your battery (negatively impacting range)

 

[RivAW]

If you hit your climate control to warm up the truck ~20 mins prior to driving (AND it is plugged into the charger), then it warms the battery too. When I do that, my battery shows about 50 when I leave. If do it while the truck is not plugged in, or don't bother, the batter might be in closer to ~20 (F). I recall that there is a setting (somewhere) where you specify that you want the HVAC to pull from the charger rather than the vehicle (that may be a determining factor).

Various places tracking software wishlists indicate that a "manual preconditioning" button is in the works.

 

[Golfer04]

If you hit your climate control to warm up the truck ~20 mins prior to driving (AND it is plugged into the charger), then it warms the battery too. When I do that, my battery shows about 50 when I leave. If do it while the truck is not plugged in, or don't bother, the batter might be in closer to ~20 (F). I recall that there is a setting (somewhere) where you specify that you want the HVAC to pull from the charger rather than the vehicle (that may be a determining factor).

Various places tracking software wishlists indicate that a "manual preconditioning" button is in the works.

I think it also depends on whether you have a heat pump AND how cold your battery is. As I said in a different thread, yesterday I drove my preconditioned Tri to Normal for service. WC was minus 15F, battery was 54 degrees. I got 1.8 mi/kHw on the 50 mile trip to Normal. Battery was 42 degrees upon arrival. Drove gen 1 R1T home. Battery was 3 degrees when I left. Used 50 percent of the battery driving 50 miles. Upon arrival battery temp was 32. Threw all kinds of error warnings along the way.

 

[R1TCntrlMaIzzy]

Some yes's and some no's and lots of guesses. What makes sense is to push a button on the app an hour before you leave and it starts heating up the battery using current from the charger. Scheduling a trip in advance seems like a lot of bother. I like easy. I had a "lowly" Chevy Volt years ago and you could tell it was preconditioning the battery (when it was plugged in) because you could hear it. That's what I like about GM software. It's sensible and has the features people want and need.

Ok this topic is almost as cringeworthy, to me, like the CP/AA ones.

This has been answered.

I suggest you test this yourself, then update us all. Make sure to take pictures of before and after or it is fake news.

 

[André]

It only takes seconds to change the schedule time to an hour from when you want to leave. Hardly a bother.

Even simpler, just increase range set to start charging… when you schedule a cabin precondition it WILL NOT warm the battery unless it brings the SoC below range set and then start to charge.

 

[André]

If anything I'd say the myth is around the fact that either way you'll use nearly the same amount of electricity, it just only makes a difference if you care whether that's coming from your house (which may have a time of use billing where it isn't advantageous) or from your battery (negatively impacting range)

It does make a difference if you need to use the full range of the battery pack… I don’t care where the energy comes from but if it comes from the battery it will reduce the available range. Now if the OP is only doing 50 miles it shouldn’t matter as you say.

 

[Brian-MS90D]

Thanks to all those who contributed positive good comments (which I learned from).

@Singletracker , one variable that can cause different results is the battery state of charge.

Others made good points about preconditioning being primarily beneficial for maximizing range. Other than that, preconditioning is possibly using a lot more total energy than not preconditioning.

And, a point nobody else mentioned yet (unless I missed it), if preconditioning when not really needed (i.e., you're just obsessed with the battery being warm) you're also technically decreasing your battery lifespan because the energy for both the battery and climate heating goes through your battery pack (i.e., it would contribute to the life cycling of your battery pack). I admit that such battery degradation may be minimal, but we're already talking about mostly miniscule details with preconditioning a battery for a 50 mile drive.

 

[ndmiller]

If anything I'd say the myth is around the fact that either way you'll use nearly the same amount of electricity, it just only makes a difference if you care whether that's coming from your house (which may have a time of use billing where it isn't advantageous) or from your battery (negatively impacting range)

100% your new myth based on changing the parameters of the conversation to add total energy used.

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.

I'm out welcome to ignore.

 

[Singletracker]

Thanks to all those who contributed positive good comments (which I learned from).

@Singletracker , one variable that can cause different results is the battery state of charge.

FWIW, my HVB was at approximately 60% SOC when I started the drive I referenced - not exactly in what I understand to be peak performance range. Like I’ve said, there are a lot of theories floating around regarding these performance issues, with a lot of people experiencing different results under different conditions. I don’t think I have heard anybody claim, reliably, that they have found the Holy Grail and can reproduce results consistently. Ya know, if I do A, under conditions B, I will get results C, or darn close to it, every time. That’s just not been my experience In 15,000+ miles with my ‘23 R1T. Sometimes, I can go 4,5,6 days getting spectacular efficiency #’s. Then, suddenly, I go several days with the efficiency tanking. WTF! Then, just as quickly, it can revert to great. During these periods, I’m essentially driving under the same conditions. I think my T is messing with me. It’s great to have a ride with a sense of humor ?

 

[cardad]

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?

Unless you need the range it doesn’t matter. The energy is being used whether it comes from the grid or your vehicle. Obviously more efficient when it comes from the grid.

Pro tip here is to keep your vehicle plugged in at all times and dial down the amperage to the lowest or even better run a 120 V charger and this will provide constant battery warming without having to overcharge. This also keeps your garage and cabin reasonably toasty.

 

[bmedfo1]

What we need is a "finish charging at x:xx" most of us have 15-20% to replenish daily to keep our personal preferred morning SOC. The battery is heated as byproduct of charging. most the time this is wasted energy as it happens in the evening or middle of the night and the battery slowy cools back down by morning.

Pulling extra power from the home to improve M/KW is a net loss:
Assuming you are paying your own electricity bill and you care about efficiency for any reason other than max range.

What I do:

Set the max charge low (like 75%) turn it up to 100% when I wake up. about an hour = 10% charge and will also add about 10-20 deg to the battery

Do the math and set the charge to start the night before at approximately the right amount of time to have the desired SOC at the time I plan to depart the next day. For example I am at 60% SOC and want to be at 80% SOC tomorrow morning at 6am. I would set my charge scchedule to not start charging until 4am.

Or I just dont worry about it. But for me the decreased performance is the drawback not the mileage. not that I am full throttle all the time but I hate the idea that untill my battery is over 50 deg my power is limited.

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