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Battery heating while preconditioning cabin

derotam

Member
Oct 31, 2018
825
702
Oak Hill, VA
Thanks for the graph! If you draw a horizontal line at the 14KW/10MPH point the area under the curve appears to be about 1/4 of the total area under the green curve on your graph. Better than nothing if I am analyzing this correctly.

Going 60 MPH down hill and that 14KW regen is going to be practically unnoticeable I think
 

jalatontarzan

Member
Oct 27, 2019
17
33
Finland
Going 60 MPH down hill and that 14KW regen is going to be practically unnoticeable I think
It's not going to be enough to decelerate you in any significant way at higher speeds, but it's better than nothing and otherwise lost energy would be harvested to something much more usable (heating battery and/or cabin). And 14kW for those purposes is plenty. Even if you have to apply brakes to decelerate or maintain speed in deep down hill, it's a no brainer to harvest any energy available, especially in colder climates.

I personally would like to have more customisable regen options. For example if cabin temp below certain treshold, crank up all the heating elements while decelerating to maximise energy harvesting from otherwise lost kinetic energy. I admit those kind of settings could spiral out of the casual drivers comfort zone and perhaps better to keep it simpler :D
 
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derotam

Member
Oct 31, 2018
825
702
Oak Hill, VA
It's not going to be enough to decelerate you in any significant way at higher speeds, but it's better than nothing and otherwise lost energy would be harvested to something much more usable (heating battery and/or cabin). And 14kW for those purposes is plenty. Even if you have to apply brakes to decelerate or maintain speed in deep down hill, it's a no brainer to harvest any energy available, especially in colder climates.

I personally would like to have more customisable regen options. For example if cabin temp below certain treshold, crank up all the heating elements while decelerating to maximise energy harvesting from otherwise lost kinetic energy. I admit those kind of settings could spiral out of the casual drivers comfort zone and perhaps better to keep it simpler :D

Too complex of an implementation for the few people that would actually use it me thinks.

Wouldbi use it, probably.
 
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elptxjc

Member
Dec 15, 2019
773
150
El Paso, TX
Hey gang, since we're stuck with heating the battery as well as the cabin for the time being (hopefully it'll be corrected in the future), what's the best compromise to heat the battery pack, have regen, and minimize energy (range) lost? Maybe 3 minutes when it's 50F? And 5 at 30? We're doing about 3 minutes, with seat heaters at level 2. Thx.
 

zannman

Member
May 15, 2019
133
101
Ohio
I responded in another thread when I noticed this behavior and the battery heating icon in the app for the Model 3. Apparently it has existed (and worked) for quite some time in the Model S.

I ran a test on a cold soaked Model 3 at 32*F, and per TeslaFi - not ScanMyTesla - saw the following with the car plugged in and capable of pulling 7kw @ 30A.

0-15m - Cabin Preheat and presumably stator heaters full on - SOC dropped from 90 to 87.
15m-45m - Cabin temperature stable and presumably stator heaters full on - SOC stable at 87.
45m-55m - Cabin temperature stable and stator heaters cutting back - SOC rising back to 90.
55m-onward - SOC remained at 90 while preheating still on for a period of time. Battery heat icon off.

This would suggest that for short trips, the optimal preheat time would be no more than 15 minutes - or when cabin temperature was comfortable and usage of about 3kWh by that point.

I wonder if in addition to helping cold weather regen, this new behavior assists the heat pump in newer cars.
 
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GZDongles

Member
Feb 23, 2020
224
283
Michigan
I don't think any behavior has changed with preconditioning, just the icon is new. You could see the motor stators working before using Scan My Tesla.

My personal philosophy is that if I'm connected to a charger that can output more than 8kW and I'm going on a long trip, I will preheat for up to an hour. I will usually charge to 95% beforehand so if I burn some off the battery it's not a big deal. The 8kW threshold is so that i at least won't lose energy from the battery from running the motor stators, and the consumption from the heater usually is in the 1-2kW range for me in Michigan winters.

Generally I'll preheat the cabin at 60° F for 30 minutes, 70° F for 20 minutes, and 75° F for 10 minutes. Then I usually can go 20-30 minutes with climate off and just seat heat when I'm driving. That's my preconditioning regimen if I really need to maximize range in the winter for long drives.

If I'm driving locally, I either won't precondition or will do it for a short amount of time just to take the edge off the cold. I find that the cabin warms up very quickly, and you'll never get back the energy you lose from preconditioning through increased regen. Personally I think it's a good idea to give the friction brakes a workout now and then anyway, especially in the winter with water and salt everywhere.
 

GZDongles

Member
Feb 23, 2020
224
283
Michigan
Thanks for the tip. Do you have to change the preheat temp manually, or is there some way to do the automatically?
I change it manually. I'm not sure if IFTTT or TeslaFi or other automation apps can be used to set a warming routine. Honestly I don't know if it would make that much difference to set the heat to 68 or 70F for the full hour, especially if you aren't planning on using all the range. I just have a very specific drive (Ann Arbor to Cincinnati) that I can barely do with a full charge if I preheat aggressively and am very careful with consumption while driving. I also have the option of stopping at a rare supercharger that's completely free, so I'm tending to opt for a few minutes there so I arrive with some buffer anyway.
 
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derotam

Member
Oct 31, 2018
825
702
Oak Hill, VA
Hey gang, since we're stuck with heating the battery as well as the cabin for the time being (hopefully it'll be corrected in the future), what's the best compromise to heat the battery pack, have regen, and minimize energy (range) lost? Maybe 3 minutes when it's 50F? And 5 at 30? We're doing about 3 minutes, with seat heaters at level 2. Thx.

If you are trying to heat a cold soaked battery at say 32F, specifically for regen,your looking at at least 30 minutes to an hour to get it up to temp(at least 14C for full regen).

I will note that with previous firmwares last March, full regen wasn't till battery temp >18 as shown by SMT. It is less now from a quick look while on a recent trip so ill need to re-look at that temp vs regen curve again.
 

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