AlanSubie4Life
Efficiency Obsessed Member
That’s for preconditioning the vehicle.
It wouldn’t make any sense to waste energy keeping the battery warm.
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Model 3 SR+ LFP Battery Range, Degradation, etc Discussion
- Thread starter Baluchi
- Start date
It wouldn’t make any sense to waste energy keeping the battery warm.
The purpose of preconditioning is not “to keep the battery warm” though. Maybe preconditioning is what Tesla had in mind, but if so, they used incorrect wording in that part of the manual. Preconditioning is defined in other parts of the manual, and in those places, they say it “warms the battery”. Different verb, but maybe I’m reading into it too much.
I could see a use case for keeping the battery warm for a relatively short period of time (up to 24 hours) in extreme cold. Efficiency, especially in LFP cars, will tank in extreme cold, so it could be more efficient to use a little battery to maintain some minimum temperature for a while after parking than just completely letting it go and using a massive amount of energy to precondition. Usually with home air conditioning systems, if the outside temperature is extreme, it takes less energy to keep a house near a temperature when you’re gone to work for 8-12 hours than just completely turning off the system during that time and making it work hard to bring the temperature back when you get home from work. Same principle could apply here, I think.
I have used Scan My tesla since the car was new, also use teslalogger so all scan my tesla data is logged and I also have teslafi logs since new. (2 1/3 year).
The teslalogger logs also shows when battery heating is active, and it just aint when the car is parked.
Is that picturere from the most recent manual or from the online version?
I can not find that i formation.
I live in a cold climate.
If I leave the car at work not driven for a week (outside) the battery temp goes down to the ambient. It takes a while to reach ambient but during this time no energy is drawn from the battery.
I can see when charging outside in cold with the UMC charger at low power (2-3kW) that the battery heat needed to keep the battery at least a little above freezing is way more than sentry mode. Like closer to 1 kW or so, so the car would drain from 100 to 0% in a few days, if this was true.
If plugged in as recommended we really only have two choices, either use scheduled charging or not.
At scheduled charging the car will be charged each day, which heats the battery either by charging alone, or if the cell temp is below freezing also by heating the battery.
If not using scheduled charging, I havent really ised this much, but then the charging starts as soon as the cable is connected, and I guess re-charges quite often if needed.
Why would the car use energy to keep the battery warm? It would be expensive in terms of electrical use, and also increase the cycles on the battery.
The car was connected (UMC) and chsrged in the morning of 25DEC 2022. This means, the battery was kept at at least 8-9C during charging.
This is the same day, 5PM
ambient = -19C for borh pictures.
This is the same day, 10PM
I also might have logs, but the logs is only active when the car is not sleeping (sleeping - HV batt disconnected so no battery heating) and the tablet mostly shut down due to too cold when parked.
’twas a long post.
Summary: the ”keeps the battery warm” is a myth.
Above post was with the car connected with the UMC.
I have the same for parked in cold with the car not connected. The SOC doesnt drop at all. The on screen displayed SOC drops but teslafi shows both the cold SOC and the non cooled battery SOC, so I can see the energy vontent of the battery. It foes not drop, and it would need to drop to warm the battery when the car is not connected.
Summary: the ”keeps the battery warm” is a myth.
Above post was with the car connected with the UMC.
I have the same for parked in cold with the car not connected. The SOC doesnt drop at all. The on screen displayed SOC drops but teslafi shows both the cold SOC and the non cooled battery SOC, so I can see the energy vontent of the battery. It foes not drop, and it would need to drop to warm the battery when the car is not connected.
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Oh, I read the whole thing and very much appreciate it! Sometimes I have trouble believing things when people just say “you’re wrong”, but when you lay out all of the data and reasons that led you to that conclusion, I can believe you 100% now!
The screenshot I posted was from the most recent manual in the app, by the way. It’s in Driving > Cold Weather Best Practices > Scroll way down to After Driving. For some reason, the search function is bad and doesn’t find it.
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When either preconditioning on timer, starting the AC/heater with the app or simply entering a car for a drive, the battery is heated if needed and this do not take long.
So it is more energy saving to only heat the battery when the need comes, than to keep it warm for hours.
Yes, the battery heat seem to be a wide spread myth. I do not know if it started as a myth or if Tesla actually did keep the batterys warm before, in early model S or so.
Whats clear is that it would drain the battery very quick if they did, so I would guess that they didnt…but I do not know.
I see in some Swedish forums that these myths are circulating just about every day:
- Battery warming
- LV batt not charged above 6 or 20%
- Low SOC is bad for the battery
- 100% SOC must be driven of asap
-80% is the best to preserve the battery
And a few more.
In many cases it is not even worth trying to correct, as people as very rigid in what they “know”.
A add on to the pcitures above:
The cell temp log. The car was sleeping from the charging was completed (circa 6AM). so the straight line is drawn straight between two log points until about 16:45 (4:45PM), where we have a data point (med entering the car for the forst picture in the post above). In real life, the battery cools quicker initially and slower the closer to the ambient it gets, so it should be a bent line if it was constantly logged. Next point was shortly after 22 (10PM) when I entered the car and sat in it for a while to chech a lot of SMT values. Thats the reason the battery was wamred, me inside with the cabin heating on.
For battery heat, I have logs for this as well. The red lines is the battery heat, it is logged as on (100%) or off( 0%). The battery was heated from -6C to +8.5C when the charging was set to start by schedule. As seen, there was no battery heating going on after the charge this day.
The tablet is set up to start and send logs as soon as the car is not sleeping. One of the reasons for sitting ling time after 10PM was to ensure the tablet was heated and charged a bit, as it otherwise shut down when the tablet battery gets too cold, preventing med from getting logs. I was doing some logging just for the reason of the battery heating myth. There is some other posts here by me on this as well.
If the car had heated the battery, the HV batt had been connected and than my tablet would have been sending SMT logs to the teslalogger server. So we can sefely sy that there was no battery heat going on after the charing was complete.
The cell temp log. The car was sleeping from the charging was completed (circa 6AM). so the straight line is drawn straight between two log points until about 16:45 (4:45PM), where we have a data point (med entering the car for the forst picture in the post above). In real life, the battery cools quicker initially and slower the closer to the ambient it gets, so it should be a bent line if it was constantly logged. Next point was shortly after 22 (10PM) when I entered the car and sat in it for a while to chech a lot of SMT values. Thats the reason the battery was wamred, me inside with the cabin heating on.
For battery heat, I have logs for this as well. The red lines is the battery heat, it is logged as on (100%) or off( 0%). The battery was heated from -6C to +8.5C when the charging was set to start by schedule. As seen, there was no battery heating going on after the charge this day.
The tablet is set up to start and send logs as soon as the car is not sleeping. One of the reasons for sitting ling time after 10PM was to ensure the tablet was heated and charged a bit, as it otherwise shut down when the tablet battery gets too cold, preventing med from getting logs. I was doing some logging just for the reason of the battery heating myth. There is some other posts here by me on this as well.
If the car had heated the battery, the HV batt had been connected and than my tablet would have been sending SMT logs to the teslalogger server. So we can sefely sy that there was no battery heat going on after the charing was complete.
We can also see that the battery warms quite quick. When driving the car doesnt heat it very much, only to just above freezing.
This means, leaving the car at -20C for 16hours might cool it to -6C, and when starting to drive it will reach above freezing ( 0C) in much
less than 30 minutes.
This means, leaving the car at -20C for 16hours might cool it to -6C, and when starting to drive it will reach above freezing ( 0C) in much
Here's a trip in -22C, started from my garage, with a recent charge, thats why the cell temp was 20C.
Drive to our frinds was between 16:30 and 17:09, and preheating/conditioning before driving home started circa 20:30, and the drive home was 20:48 to 21:17.
Battery heater was only on during the preconditioning before driving home.
This is the teslafi log from this time:
Parked with 54% SOC and 53 % when starring the preconditioning before the drive. Sentry was on, as I have it on except at home/work etc, so that percent we lost was most probably sentry use. There simply was no possibillity that the battery hade ben kept warm from its own energy as no energy was used for this.
With this I think we have settled the question and that these posts maybe can be used again to show that the battery isnt kept warm as per the myth.
Drive to our frinds was between 16:30 and 17:09, and preheating/conditioning before driving home started circa 20:30, and the drive home was 20:48 to 21:17.
Battery heater was only on during the preconditioning before driving home.
This is the teslafi log from this time:
Parked with 54% SOC and 53 % when starring the preconditioning before the drive. Sentry was on, as I have it on except at home/work etc, so that percent we lost was most probably sentry use. There simply was no possibillity that the battery hade ben kept warm from its own energy as no energy was used for this.
With this I think we have settled the question and that these posts maybe can be used again to show that the battery isnt kept warm as per the myth.
Candleflame
Active Member
It's not degradation, it's the computer adjusting the range estimate based on your driving, weather, road conditions, etc. "Your mileage may vary."
arichard2401
Member
I recommend switching to percentage instead of miles and you'll never have to worry about it. That miles remaining figure is not particularly accurate, certainly not accurate enough to sweat 3 miles. Also you're never going to drive that down to zero miles so having the total miles displayed isn't giving you an accurate idea of how far you can actually go before a charge.
The range at the battery symbol on the display does not adjust for driving, weather, road condition etc.
It is the estimated energy content of the battery divided with a fixed consumption/mile or km.
The fixed value is the EPA consumption.
For example, my car always will show 507km or 315 miles if the battery has a content of 80.5 kWh.
The loss of range for OP cones from both the initial degradation whickh is higher in the beginning, and also the inaccurancy of the BMS to properly estimate the battery capacity at all times.
I have my model 3 FLP battery for 2 months. So far I have changed it 8 times each time to %100. This means 8x272mil=2,176 miles of range but I just got 900 miles of driving!!! I turn off century mode and departure/charging schedule. Yet last night alone I lost %17 of battery charge as car was parked and nothing that I knew was working in the car. Does anyone experience this much of charge loss? Does anyone have any clue why this might be?
My car's build date is April 24, 2022 so today marks the 1 year of the car using the battery. ( I only received the car May 13th)
I constantly charge to 100%, mainly charge by Level 1 at home and Supercharge for road trips.
Sitting at 19640 km's (12200 miles) and the full displayed range at 100% is now 424 kms.
When new it displayed 438 so a loss of 14 kms works out to about 3% degradation in 1 year of use in temps of 35°C to -35°C
So IMHO I think this is good
I constantly charge to 100%, mainly charge by Level 1 at home and Supercharge for road trips.
Sitting at 19640 km's (12200 miles) and the full displayed range at 100% is now 424 kms.
When new it displayed 438 so a loss of 14 kms works out to about 3% degradation in 1 year of use in temps of 35°C to -35°C
So IMHO I think this is good
My M3 RWD build date was mid March 2022. I now have 35400km (I put ~9000km on it going to and from SE AZ over the winter) on the clock and my displayed range at 100% SOC also equals 424km. I currently L1 (L2 in AZ) charge to 100% several times per week (basically at every opportunity with my 8A/110v L1 charging station).
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