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Preconditioning for fast charging, worth it?
- Thread starter davraker
- Start date
ZenRockGarden
Active Member
Efficiency - total use of power.
You're spending a few KWH to prep the battery pack. Do you save at least that much power in the now-preconditioned charging process?
Thermal throttling can definitely happen when the battery is too hot. Just watch bjorn's videos, lol. There are many (non teslas), that thermal throttled when the battery was too hot... Kia EV6 being one, that he mentioned had subpar thermal management, where if the climate control was cooling the cabin, it couldn't simultaneously cool the battery. He showed on the OBD scanner, that when the cabin climate was on, when it was hot outside the battery termperature went above 50 degrees celcius, and the charge rate when down... When he turned off the cabin climate, it started cooling the battery. Likewise, he showed when he was done with charging, and the battery was at 50 degrees celcius, the motors were thermal limited to 60 kw until the temps came down, making the car a bit sluggish. He pointed out, that Tesla didn't have this problem,as it was able to cool the cabin and the battery simultaneously. When it was super hot, it would show a message saying that cabin cooling is reduced, as it prioritized the battery... The Kia he pointed out didn't seem to be able to do both simultaneously, and would always seem to prioritize the cabin.
No. The energy is traded for faster charging speed… less charging time. It does not make charging more efficient and you do not get it back.
ZenRockGarden
Active Member
Well that's the point I've been talking about all along.
We all agree that pre-conditioning the pack to optimal temperature can increase charging speed and save time.
I was more interested in the slightly subtler topic - are we saving money and the planet with pre-conditioning if time is not urgent? Best I can tell it's as you say - we're trading a dollar's worth of electricity to fill the pack faster. That's a legit trade off. But it's the reality I want everyone to understand.
From my experiments there appears to be something broken with the way it does preconditioning at least in some firmware/vehicle combinations.
It used to precondition about 30 minutes before the destination supercharger, but after the update it started as soon as you enter in the destination supercharger even if its 90+ miles away. If you click the preconditioning notification is does not turn it off, and instead it just removes the notification.
I don't have a Model Y, but a 2018 Model 3. The way battery heating works in a 2018 Model 3 is it runs the motors in an inefficient manner to warm up the battery, and you can hear a whine when it does this.
On my last road trip I decided to test out a theory.
The theory was that the total energy used by preconditioning would be the same regardless of when it started. That I could simply allow it to do its thing, and not worry about it. That it would determine the best way to get the battery to temp before reaching the supercharger.
With a 90% charge I entered in the destination supercharger which was a little over 90 miles away, and it immediately indicated that it was preconditioning. The trip planner was estimating 34% at the destination which makes sense as it normally says around 40% without preconditioning. FYI - You can test this yourself by entering in the destination supercharger and then looking at the trip planner after the preconditioning starts, and then look at it when you've entered in a nearby destination. There will be about a 6-8% (or so) difference.
During the first 30 minutes of driving the destination estimate in the trip planner kept dropping. I figured eventually it would settle out, but it didn't. When it got down to 20% I selected a different destination to get it to turn off.
Then today I finally remembered to chat with Tesla between 8am and 3pm PST to see if they knew how preconditioning was supposed to work. When they heard my story they said it was abnormal energy usage, and to schedule a service appointment. I did that, but I'm expecting service to cancel it. If they do I hope they push it up the chain as I believe its a bug and it has nothing to do with my vehicle.
The temperature I've been testing it in is normal PNW 45F weather.
It used to precondition about 30 minutes before the destination supercharger, but after the update it started as soon as you enter in the destination supercharger even if its 90+ miles away. If you click the preconditioning notification is does not turn it off, and instead it just removes the notification.
I don't have a Model Y, but a 2018 Model 3. The way battery heating works in a 2018 Model 3 is it runs the motors in an inefficient manner to warm up the battery, and you can hear a whine when it does this.
On my last road trip I decided to test out a theory.
The theory was that the total energy used by preconditioning would be the same regardless of when it started. That I could simply allow it to do its thing, and not worry about it. That it would determine the best way to get the battery to temp before reaching the supercharger.
With a 90% charge I entered in the destination supercharger which was a little over 90 miles away, and it immediately indicated that it was preconditioning. The trip planner was estimating 34% at the destination which makes sense as it normally says around 40% without preconditioning. FYI - You can test this yourself by entering in the destination supercharger and then looking at the trip planner after the preconditioning starts, and then look at it when you've entered in a nearby destination. There will be about a 6-8% (or so) difference.
During the first 30 minutes of driving the destination estimate in the trip planner kept dropping. I figured eventually it would settle out, but it didn't. When it got down to 20% I selected a different destination to get it to turn off.
Then today I finally remembered to chat with Tesla between 8am and 3pm PST to see if they knew how preconditioning was supposed to work. When they heard my story they said it was abnormal energy usage, and to schedule a service appointment. I did that, but I'm expecting service to cancel it. If they do I hope they push it up the chain as I believe its a bug and it has nothing to do with my vehicle.
The temperature I've been testing it in is normal PNW 45F weather.
I was driving up the 5 a few weeks ago heading towards the supercharger in Tumwater. My car said it was preconditioning the batteries sporadically off and on, about 70 miles before the supercharger. It seems to always do that since last fall.. The only time I noticed a much lower arrival SoC than usual, is when I made the same trip in heavy rain.
Good info. But you need to complete the experiment and include the cost of getting back up to say 90% SOC and the total time. Maybe that much more preconditioning allowed even faster charging and not that much to net cost?
Love the fact that Tesla has figured out how to precondition the battery for better supercharging. Just shows they're ahead of the competition in how properly setting up a BEV vehicle can help minimize the difference in GAS vs BEV "refueling".
Whenever I'm supercharging I want to get my charge and go, If I'm at charging at home/destination charging, I could care less how long it takes.
Just finished a 2,200 mile spring break trip, the vehicle preconditioned sometimes a long way from the next supercharging stop, sometimes not as far. I figure It has to do with many different variables. It never left me short on charge to reach the next supercharging stop and assists in getting me on my way faster.
Whenever I'm supercharging I want to get my charge and go, If I'm at charging at home/destination charging, I could care less how long it takes.
Just finished a 2,200 mile spring break trip, the vehicle preconditioned sometimes a long way from the next supercharging stop, sometimes not as far. I figure It has to do with many different variables. It never left me short on charge to reach the next supercharging stop and assists in getting me on my way faster.
We did a trip in a Model 3 around the ring road in Iceland last summer and really wished we could've manually enabled preconditioning or that it could be enabled for non-Supercharger level 3 charging. There were many locations around the country where we had to use the ON network since there were no Superchargers nearby. Even after driving for hours, the cool temperatures and low speed limits prevented the battery from warming up sufficiently from driving alone. While most of the ON chargers were 50 kW max, we were lucky if the charging started at 30 kW when we plugged and it usually took nearly an hour before the car was able to ramp up to 50 kW. In parts of the country where Supercharging (and preconditioning) was available, we were able to plug in and instantly charge at 150 kW at v2 Superchargers and 250 kW at v3 Superchargers, greatly reducing the amount of time we spent charging.
After picking up my Model Y at Mt. Kisco in May of 2021, I stayed the night at my sister's house in Manchester, Ct before driving back to Rochester, NY. Overnight I charged the car to 100%. As soon as I entered my destination at the start of the trip back, the car immediately started 'preconditioning the battery for faster Supercharging' even though the Supercharging station was over 200 miles away and I had 322 miles of range indicating. The temperature was moderate (57 Deg - see attached photo) and the energy consumption skyrocketed to the point that it was obvious that I would never make it to the Supercharger. I'm with the group that thinks this is a bug. Since then, I've just entered a destination near the supercharger to prevent preconditioning - it never seems to limit the Supercharging rate. I just recently learned about tapping the message on the screen to turn off preconditioning. I'll have to test that out.
So is preconditioning not clever enough to balance range with energy consumption? Sounds like a stupid implementation if I would end up short of reaching my supercharger because of preconditioning to reduce charge time once I'm there.... Can someone confirm that has actually happened to them?
How was the weather otherwise? 57 degrees is definitely on the cool side for the battery. I have an insulated garage, so 55 degrees is a normal temperature in my garage in the fall/spring, and I know at that temperature, my car will have limited regen going down our hill.... Also... I go on the same roadtrip every few weeks for work... I don't think there was any way you were going to make that supercharger 200 miles away in 57 degree weather, even if you weren't preconditioning, especially if you are driving faster than 55 mph. I think it was just a coincidence that it started preconditioning early and then you didn't have enough juice to make it to your supercharger. In my experience, my car will tell my it is preconditioning the batteries, than when the battery gets to optimum temperature, it stops... And then will cycle back on later if the battery cools significantly.. I've never had it impact my range to the point that I can't get to the intended supercharger.
I think what compounded your situation, is that if you just picked up your car, it had no consumption data to offer a realistic range estimate when you entered in a navigation destination, so all it had to go by was EPA estimated data, which makes a lot of assumptions about your driving and current conditions. Even in warm weather, I don't enter in a SC destination that is over 200 miles away. I don't think I would ever make it there, at least not at the speeds I drive at.
In my experience, the estimated SoC on the navigation screen has always been spot on since I can remember looking at it. (I didn't really pay attention to what it said the first month or two as I was learning the car). I've also learned to add about a 10% buffer due to weather conditions, if it is raining/windy/etc.. Regardless if my car is preconditioning or not, the estimated SoC has typically been pretty spot on, with the exception of weather relating things, but even then it was only off by < 10% or so.
Also, your 322 miles of indicated range... I assume you were looking at the battery icon on the top of the display? If so, that indicated range is way off if you have it showing miles left. You really should have it display %, and you should be looking at estimated SoC on arrival on your navigation screen... Otherwise your car really has no idea where you are driving to, so it can't take into account important factors, like elevation change, estimated speed/consumption, etc.
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It won't work. :-(
My model 3 continues to make the same preconditioning whine after a tap the notification in my testing.
From a UI standpoint it makes sense as taping a notification usually removes a notification, and doesn't turn something off.
Ideally it would be locked where taping it would switch between Off/On/Auto.
Yeah, there is some additional experiments to be run.
#1 - No preconditioning from my House to the Centralia V2 Supercharger.
#2 - Auto Preconditioning from my House to the Centralia V2 Supercharger. This was what I hoped to do with my previous experiment, but I bailed on it when the estimate for the destination got to 20%. That's a LOT of energy to use for a little under 100 miles.
#3 - Manual preconditioning where I switch the destination to the supercharger about 30 minutes out to allow it to precondition. This is normally what I do.
There are a lot of variabilities so its a hard test to run. The traffic speeds can differ a lot, the Centralia supercharger is often more than half full which would mean charging up less quickly due the shared nature. There is also variability in rain/wind.
Based on what I already know I believe #3 will use around 6-7% of the battery range in exchange for 5-10 minutes quicker charge. #2 clearly already uses at least 10% more without any gain. It's not like a V2 supercharger can charge much faster than it already does with 30 min of preconditioning like it used to do.
Never seen anything like this. If it's warm out, the car sometimes doesn't precondition at all. If it's cold, it starts earlier, but definitely not that far away.
Here are my latest two trips when preconditioning. The legs highlighted in yellow were when preconditioning. The two circled in green were the same trips, but the terminal leg when I wasn't heading to a supercharger. There are impacts from the elevation, speed, and temperature swings, but the first leg shows 490 Wh/mi even when I was averaging down hill. I never see 400+ Wh/mi on trips unless I'm preconditioning in the winter.
Perhaps the impact I observed was greater due to the low temperatures because there probably isn't any waste heat. Heating that massive battery from 20 degrees to 120 degrees takes a lot of energy.
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I think there's a lot more going on based on your numbers than meets the eye... I think that first dataset with the 490 wh/mile is an outlayer... If you look at your other data sets:
You second one, shows that over 76 miles you averaged 65mph @ 407 WH/mi, with +389ft elevation gain while preconditioning
Your last one, shows that over 70 miles, you averaged 58mph & 388 WH/mi, with -8ft elevation drop. It shows preconditioning, so not sure why it's marked green.
Your third one shows that over 100 miles you averaged 57mph @ 353 WH/mi with -378ft elevation drop without preconditioning.
Based on these numbers, you only consumed an additional 30 WH/mi while preconditioning between the last one and third one, which are most similar in terms of driving speed and elevation.
You second one, shows that over 76 miles you averaged 65mph @ 407 WH/mi, with +389ft elevation gain while preconditioning
Your last one, shows that over 70 miles, you averaged 58mph & 388 WH/mi, with -8ft elevation drop. It shows preconditioning, so not sure why it's marked green.
Your third one shows that over 100 miles you averaged 57mph @ 353 WH/mi with -378ft elevation drop without preconditioning.
Based on these numbers, you only consumed an additional 30 WH/mi while preconditioning between the last one and third one, which are most similar in terms of driving speed and elevation.
Yes - the "stupid implementation" is what most people are complaining about here. I'm sure that someone has run out because of preconditioning, though I wouldn't be surprised if preconditioning turned off below 20% SOC like a lot of other things do.
You have perfectly explained why the current implementation of preconditioning is dumb. All the car needs to do is do this:
- Calculate estimated time to Supercharger
- Calculate estimated charge level at arrival
- Look at maximum charge speeds of Supercharger (V3, V2 or urban)
- Look at battery temperature
- Calculate optimal battery temperature for available Supercharger speeds
- Calculate time to heat battery to target to target temperature
- If time to heat battery <= time to arrive at Supercharger, turn on the battery heater
If one could run those experiments while using ScanMyTesla to record what the car is doing - eg knowing start battery temperature, temperature along the way along with temperature targets along with state of charge, that would be super interesting. And then when you get to the SC and start charging, knowing the charge rate, SOC and battery temperature and targets would also be informative.
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