To be clear, I was not suggesting that battery heating during charging will make much difference for regen braking. My point is that charging during the evening and then letting the car sit for several hours before preconditioning throws away any battery heating that may occur as it is being charged. BTW I can achieve almost full regen in the morning after preheating in an 8C garage, but at the end of the day with the car parked outside below freezing I have yet to achieve close to the same level of regen even after preconditioning. TezLab shows those drives being 15-20% less efficient than the morning.
-
Want to remove ads? Register an account and login to see fewer ads, and become a Supporting Member to remove almost all ads.
Preconditioning
- Thread starter AdrianLev
- Start date
To be clear, I was not suggesting that battery heating during charging will make much difference for regen braking. My point is that charging during the evening and then letting the car sit for several hours before preconditioning throws away any battery heating that may occur as it is being charged. BTW I can achieve almost full regen in the morning after preheating in an 8C garage, but at the end of the day with the car parked outside below freezing I have yet to achieve close to the same level of regen even after preconditioning. TezLab shows those drives being 15-20% less efficient than the morning.
If preconditioning is performed only an hour or so after charging the battery pack will still retain some heat from charging. How long do you precondition? I find that at colder temperatures, i.e. below 0C, I need to precondition for at least 30 minutes to have adequate but not nearly full regen. (I try to count the little dots at the top of the Driving screen but they are too small. Up to about 10 dots, the available regen is adequate.) I have driven without preconditioning and the lack of any useful regen caused me to adjust my driving to allow for braking.
In a different thread someone posted that during charging the battery was only warmed to 10-12C; when preconditioning the battery would be warmed to 20-22C.
I've only been preconditioning for about 15 mins, just enough to warm the cabin. I haven't been thinking in terms of the extra time that might be required to fully warm the battery because I'm not convinced it's necessary. This morning I left heat on for longer and departed with no regen dots, although 4 or 5 appeared during the drive (20 mins at -9C). This afternoon after being parked the cabin was at -1C and I ran heat for 25 mins. At the end of that period there was no battery symbol on the app climate page but there were still 8 regen dots on the screen. Preconditioning consumed 25 km of nominal range (~ 5% SoC). Regen during the drive was quite adequate though. However, the "limited regen" alert came up for the last 10 mins of the drive even though there was no apparent change in the number of dots from when I set off. In spite of this, the TezLab drive efficiency was still only 55% (44 km used vs 25 km travelled) compared to 78% in the morning, and not much different from my normal afternoon drive performance so I didn't see any advantage from the longer preconditioning period.
I prefer to precondition for longer than ~10 minutes, closer to 30 minutes in cold weather. I appreciate having full or nearly full regen capability when I start driving. Most of my trips are under 5 miles so I don't usually see the limited regen warning unless I make several short trips after preconditioning. About 5 out of 7 mornings I am able to charge for ~90 minutes at a free public charger (6kW) so my efficiency may be low but my cost per mile is practically zero.
I don't like mysteries so I played around a bit this weekend to assess the impact of preconditioning. I tried driving my usual route (at -6C) with no preconditioning morning or afternoon, and the results were essentially the same as I had before with preconditioning. I also had the opportunity to do the same round-trip twice in a day with a warmed-up car. In all cases, the outbound leg from home was always more efficient than the return (by 15-20%). Then I realized that there is a longer stretch of highway with a higher speed limit for the return trip, and the difference in efficiency values was reduced when I maintained the same speed in both directions. I even took snapshots of actual vs nominal distance travelled and energy consumption rates during the trip and compared the results for different directions at the same geographical locations. The return trip efficiency still tended to be lower, even at the same speeds. There's negligible elevation change and I eliminated all the other variables I could think of, so I have to assume that the remaining difference was due to wind. It comes from the west most of the time, which would help me on the outbound trips and impede the return. All this to say that the reduced efficiency for my afternoon drive, which I was attributing to a colder battery, seems to be caused by other factors.
I don't know if it's just a coincidence, but I feel I'm seeing fewer regen dots for the same outside temperatures compared to a few days ago. I installed the latest SW update during this period but the release notes only mention bug fixes, nothing about improving regen availability.
I don't know if it's just a coincidence, but I feel I'm seeing fewer regen dots for the same outside temperatures compared to a few days ago. I installed the latest SW update during this period but the release notes only mention bug fixes, nothing about improving regen availability.
I am new here and a relatively new Tesla MY owner (less than 2 months). I was wondering around what temperature is advised to precondition the battery? I have noticed that even when it is around 50F, if I turn on the climate before heading to the car, the red battery with the snowflake will still pop up at times. I don't currently park it in an indoor garage, so I want to make sure I do what's best for the car long term.
The benefit of preconditioning is to warm the battery so that there is some but not full regenerative braking in colder temperatures. A second benefit is that the cabin can be preheated for passenger comfort. If you live where the temperature does not get much below 50F you can use the seat heaters and the heated steering wheel, dress warmly and you won't need to precondition to warm the cabin. The downside of not preconditioning is the lack of regenerative braking when the battery is cold, especially once you expect regenerative braking to be available, forces you to change your driving and use the brake pedal.
Thank you for the quick response! I sure like to get into a 70F car when it is 45 outside, but it sounds like there is no real long term harm in not doing it every time I get ready to go, except for the few nights a year when the temperature goes below 40, I guess.
Nothing bad will happen to the Tesla if the temperature drops below 40F. As the temperature drops you will see one or more snow flake(s) on the battery on the Tesla app. This indicates that the battery is too cold to charge, too cold for regenerative braking and too cold to deliver full power. As you drive the Tesla the battery will gradually warm up. Do use the Climate Control while driving; 68 to 70F on Auto so the windows don't fog up.
I've noticed the same thing. Not only are there fewer regen dots then there used to be at the same temperature, the battery warming function also does not appear to be triggered in the same temperature range. I believe the newest software requires the battery to be colder before it starts to limit regen and/or use the motors to heat the battery.
alexcue
Member
Just noticed that too... something changed in the last update and battery warmup is less pronounced given the same outside temperature. What's interesting is the warning about Regen not being available seem to come off and on now. Like they introduced a new bug, even when I've tried to Pre-condition for the same time as I did before. Before, it warmed up the battery enough and no regen warnings would appear.
Granted this is SoCal, where I've been averaging about 48-52*F for about the last month or so in the morning when I leave for work.
I've been getting a bit distressed seeing more and more threads being started by new owners who seem to be misled into this thinking that they have this ominous chore hanging over their heads that there is a burden on them to manipulate the temperature of the battery to prevent damage in daily use. This isn't so. There's nothing you need to do. The car has a very complete self-management of its own temperature limitations, such that there is nothing you need to do in that respect and no way you can hurt it. The car will definitely and noticeably limit its own power input and output sometimes based on temperature conditions, so you may see things like charging being slower or the regeneration braking being reduced and weaker, and things like that, but those are just signs that it knows and is handling it on its own.
Any prewarming you want to do is just for your own preference and comfort.
![angus[Y]oung](/tmc/data/avatars/l/141/141264.jpg?1620160343){kind=avatar}
angus[Y]oung
Active Member
MrWattson
Member
Sorry just saw your comment. I must have fat-fingered back in February. I did not intend to disagree and removed that. There is nothing disagreeable...lol.
@alexcue @silverstoned83 yes that seems to be a thing.... Tesla software update 2021.4.11 improves regenerative braking with cold soaked batteries - Drive Tesla Canada
So I wasn't imagining it! Thanks for the confirmation that others saw it happening too; odd that Tesla made no mention in the release notes though. The funny thing is that today at temps above freezing I was seeing a few regen dots and even got the "limited regen" alert. Anyway, here's hoping that Tesla will allow the battery to accept more regen power at low temps - it's quite disconcerting when you get above 20 dots and there's virtually no braking when you lift your foot.
So I wasn't imagining it! Thanks for the confirmation that others saw it happening too; odd that Tesla made no mention in the release notes though. The funny thing is that today at temps above freezing I was seeing a few regen dots and even got the "limited regen" alert. Anyway, here's hoping that Tesla will allow the battery to accept more regen power at low temps - it's quite disconcerting when you get above 20 dots and there's virtually no braking when you lift your foot.
Completely true - thanks for the clarification. The other reason for adding heat to the battery before departure in very cold temps is to help the heat pump because it uses battery heat to help warm the cabin below -10C (14F). If the battery starts off cold in those conditions, it may get even colder as you drive -> less regen -> more friction braking -> vehicle's kinetic energy lost to heat instead of going back to the battery.
The part that I find funny is how the article makes it sound like the software update did something significant to improve regen braking. In reality, all they did was unlock more potential from the battery pack after having enough time to study how the chemistry handles certain situations. Once enough data is collected, Tesla redefines the pack’s limits in order to further maximize the potential.
I wouldn’t be surprised if the supercharging performance at cold temps is also improved.
Last edited:
Did I misread them initially, or did the release notes for 2021.4.11 originally say "bug fixes"? I looked today, and they're titled "Minor fixes - miscellaneous improvements". A bit more expansion on what that means would be helpful!
Is that really true? I still don't seem to be able to schedule it to START at 11pm (when my cheapest electricity rate starts) on 2021.4.11. Since I don't currently need to leave at a certain time (still remotely working), I don't care to have it precondition in the morning.
And for unknown reasons, even if I do set it to finish charging by 7am, most of the time it doesn't charge at all. It's possible that may have started after I began using the Tesla Stats app.
On a related note, am I missing a setting where one can choose to precondition from the battery instead of the wall unit? I like to use the app to precondition before I leave (say 11am), without having to go unplug the car. This matters because my electricity rates go way up during the day.....
Is that really true? Yes; Scheduled Charging lets you start charging at a later time. You set the start time for the charging window, also the end of the charging window. You can specify to start charging at the beginning of the charging window or to complete charging by the end of the charging window. (What changed is that you can now specify when the charging window ends, previously this was hard coded to 0600 your local time. If your off-peak charging window extends to 0700 and you normally leave by 0715 you can be assured that scheduled charging will end closer to when ou leave in the A.M.)
Scheduled Departure is where you specify preconditioning (either every day or Monday through Friday.) You can also set whether preconditioning takes place even when not plugged in. If the Tesla is plugged in during preconditioning this will draw power from the receptacle. You can't currently select to precondition only using power from the battery. To do what you want would require one of 3rd party apps or a smart EVSE that shuts off outside of the off-peak charging window.
Scheduled Departure is where you specify preconditioning (either every day or Monday through Friday.) You can also set whether preconditioning takes place even when not plugged in. If the Tesla is plugged in during preconditioning this will draw power from the receptacle. You can't currently select to precondition only using power from the battery. To do what you want would require one of 3rd party apps or a smart EVSE that shuts off outside of the off-peak charging window.
Similar threads
