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Battery and Cold Climate

davezforce

IG @davezforce
Jan 18, 2017
507
248
NJ
My raven X is a couple months old now, and getting ready for the climate to start rapidly changing here in NJ. What is the best way to Pre Heat or get the battery ready before leaving for work in the am from home and also during the day when leaving from work. I’m assuming that when I’m at home and it’s plugged in and charging that the battery is being cooled/heated as necessary. I have the charging set since I purchased it to start at 12am to 80% but noticed since the last couple days have been colder, that the charge has dropped when I’m ready to leave. It used to be exactly at 80% 239mi. Now it’s about 78% and I assume when it gets even colder it will be less than that. Should I start the charge later and try to figure out as close as possible to have it stop charging when I’m getting ready to leave? Or is there a way to have the pack warm before I actually leave while it’s still plugged in. And what do you do when your leaving work 8-10 hours later and it not plugged in. Does pre heating the cabin also warm batteries? Still new to this and just want to do what best to the car and longevity of the battery. Thanks.
 

DCGOO

Active Member
Nov 24, 2015
1,582
916
Indianapolis, IN
My raven X is a couple months old now, and getting ready for the climate to start rapidly changing here in NJ. What is the best way to Pre Heat or get the battery ready before leaving for work in the am from home and also during the day when leaving from work. I’m assuming that when I’m at home and it’s plugged in and charging that the battery is being cooled/heated as necessary. I have the charging set since I purchased it to start at 12am to 80% but noticed since the last couple days have been colder, that the charge has dropped when I’m ready to leave. It used to be exactly at 80% 239mi. Now it’s about 78% and I assume when it gets even colder it will be less than that. Should I start the charge later and try to figure out as close as possible to have it stop charging when I’m getting ready to leave? Or is there a way to have the pack warm before I actually leave while it’s still plugged in. And what do you do when your leaving work 8-10 hours later and it not plugged in. Does pre heating the cabin also warm batteries? Still new to this and just want to do what best to the car and longevity of the battery. Thanks.

Make sure the car is plugged in and turn on the Climate a couple of hours before you need to leave. You will see additional icons on the screen when it gets colder outside, indicating the battery is heating. The Battery will not be charging, but all the energy consumed by heating things comes from the shore power and not the battery until you pull the plug. You did not specify when you typically leave, but you might consider pushing the charge start time back a few hours (I start at 04:00).

But TBH, unless you have a very long commute, I really wouldn’t worry about it. The main thing that happens in winter is you energy consumption goes through the roof. But the car does a very good job of managing that for you and accurately reporting consumption.
 

davezforce

IG @davezforce
Jan 18, 2017
507
248
NJ
Thanks for the reply and information! I get up 430, leave the house 520. I suppose I could start the charging @2. Should leave enough time. It typically only needs around 2-1/2 hours to charge to 80% during the week on a normal schedule.
 

ajdelange

Active Member
Dec 10, 2018
1,077
540
Virginia/Quebec
I have the charging set since I purchased it to start at 12am to 80% but noticed since the last couple days have been colder, that the charge has dropped when I’m ready to leave. It used to be exactly at 80% 239mi. Now it’s about 78% and I assume when it gets even colder it will be less than that.
When it is plugged in it monitors SoC and when that drops to 2 -3% below what you have set it starts to charge again back up to the level you have set so you should not see anything lower than 78 (or maybe 77%).

Should I start the charge later and try to figure out as close as possible to have it stop charging when I’m getting ready to leave? Or is there a way to have the pack warm before I actually leave while it’s still plugged in.
The best way to warm the pack is to charge (or discharge it). There is a separate battery heater which comes on when the car thinks it needs it (e.g. if you are approaching a SC and the car detects that it will not be able to take full advantage of its capacity). I don't think there is a "keep battery at temp if plugged in" feature that uses it (which would be easy enough to do) hence the universal recommendations to either charge as close to departure as possible or leave climate conditioning on expecting that some of the heat going to the cabin will make its way to the battery.

Another possibility is, if you have a garage, to heat it. This will cost you, of course, but so does keeping cabin heat on when not charging.

In typical running around town scenarios the biggest problem I see with the colder weather is that regen isn't available. That isn't so much because I'm wearing brake pads and using more Wh/mi (that's just part of cold weather operation) but because the first time I have to stop and the car doesn't slow when I back off the accelerator I panic a bit because something seems dreadfully wrong for a bit. I'd like to see a flashing annunciator that reads "Regenerative Braking Limited" when it is.

And what do you do when your leaving work 8-10 hours later and it not plugged in. Does pre heating the cabin also warm batteries? Still new to this and just want to do what best to the car and longevity of the battery.
Not much can be done here. Certainly some of the heat from the cabin will make it to the battery but you have free circulation of air under the car and I'm guessing that cabin heat is only going to have a small effect therefore.
I am not aware of a "prewarm battery" feature in the app or UI (except in P models).
 

mxnym

Member
Mar 9, 2018
904
333
Bloomington, IN
Thanks for the reply and information! I get up 430, leave the house 520. I suppose I could start the charging @2. Should leave enough time. It typically only needs around 2-1/2 hours to charge to 80% during the week on a normal schedule.
That's the ticket, and if you WANT the battery to be warmed up slightly for the drive home, you can start preconditioning the vehicle at least 30 minutes before you'd leave. It will be consuming battery power to precondition, but if it is cold enough to merit doing so (has to be pretty cold, and only heats it enough for very minimal regen), it will also turn on the battery heater (consuming even more battery power). The app should indicate if the battery heater is on when you're preconditioning. I've only seen it come on a couple times, well below freezing temperatures.

ETA: I'm honestly surprised @ajdelange didn't know this, as he seems very knowledgeable, and because of this surprise, here's a link to an electrek article from December of 2017 when this battery heating feature was first added.

Tesla releases new mobile app update with battery preconditioning feature and more - Electrek

I didn't follow the link, so I don't know if/how accurate the article is, but there is no option to just turn on battery heating, the vehicle decides when you precondition (I believe the vehicle will also use the battery to heat itself less than that to prevent damage in even more severe temperatures, but that's not so relevant). Also, the 3 didn't come with a battery heater, IIRC, it stalls the permanent magnet motors and runs electricity through them to generate heat that is then moved to the battery via the "coolant" loop. Given this, it is feasible that the Raven X does the same thing since it has that kind of motor. If you don't like that idea, maybe you don't want to heat the battery more than the BMS feels absolutely necessary anyway.
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,432
7,642
Boise, ID
But TBH, unless you have a very long commute, I really wouldn’t worry about it. The main thing that happens in winter is you energy consumption goes through the roof. But the car does a very good job of managing that for you and accurately reporting consumption.
Basically this. There isn't really anything you need to do that is helpful to the car or anything like that. Any kind of prewarming routine you do is just a way of wasting more energy before you start driving instead of after you start driving. You just kind of get used to the fact that in winter, when you get in and start driving home, you are going to have 600+ watt hours per mile for the first several miles. Oh well.

The one thing that would not be entirely a waste is if you do some charging shortly before leaving. Charge needs to happen sometime anyway, so it wouldn't be entirely wasted energy preheating.
 

ajdelange

Active Member
Dec 10, 2018
1,077
540
Virginia/Quebec
ETA: I'm honestly surprised @ajdelange didn't know this, as he seems very knowledgeable, and because of this surprise, here's a link to an electrek article from December of 2017 when this battery heating feature was first added.
...but there is no option to just turn on battery heating, the vehicle decides when you precondition
That's all I really knew about this. I haven't even had the car a year yet and still have plenty to learn.

Also, the 3 didn't come with a battery heater, IIRC, it stalls the permanent magnet motors and runs electricity through them to generate heat that is then moved to the battery via the "coolant" loop.
This, I think, i one of the cleverest bits of engineering in the Teslas. Then don't have to stall the motor. They use the transistors in the inverter as heaters. There are 6. Call then Au, Al, Bu, Bl, Cu and Cl with Au, Bu and Cu all connected to the battery + and Al, Bl and Cl all connected to battery -. Au and Al are in series. So are Bu and Bl and the same for the Cs. The interconnection point of each series pair is connected to the stator winding with the same letter. In ordinary operation Au, Bl and Cl are closed and all the others opened. Current flows into the A phase winding and splits and returns though the B and C phase windings. A bit later all transistors (acting like switches) open followed by the closing of Bu, Al and Cl. Current now flows into the B phase winding and out the A and C phase windings and the direction of the magnetic field rotates 60 °. Next it's Cu, Al and Bl that are on and the field rotates another 60°. And so on. In the original designs every effort is made to have the transistors go from full off (high voltage across them but very low current) to full on (low voltage but high current) as the power dissipated in them (waste heat) is the product of voltage and current. Then some clever guy (hope Elon took him to lunch) said "lets turn all the transistors on at once but only part way. The mid point voltages of each pair is the same and no current therefore flows through the windings but neither the voltage across nor current through the transistors is very small and the transistors thus get hot. They are on heatsinks on the same coolant loop as the battery and so that "waste" heat goes to the battery. In addition, the current drawn by the transistor array heats the internal resistance of the battery and warms it further. Damn clever!

Given this, it is feasible that the Raven X does the same thing since it has that kind of motor.
There is no fundamental reason that this scheme could not be used with the induction motors of the pre-Raven design or with the induction motor of the Raven as no current goes to the motor. Redesign of the control system (the bit that sends the gating signals to the transistors) would be required. And I think they are using silicon carbide transistors in the later cars.
 
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Reactions: eml2 and mxnym

AndreyATC

Member
Dec 19, 2013
541
152
Cape Coral FL, USA
My $0.02 for winter driving
I'm in NY a few miles north of the City and temps here are about 5F colder on average
My main technique to keep the battery in better shape for commute without wasting energy is to schedule charging as close as possible to when i have to leave.
While charging (range mode is off) battery gets warm anyways, so it's usually enough to bring it to drivable condition
Also, depending on your commute, it might be enough time to get to optimal level as you drive.

For the drive back home, you can preheat the cabin.
I don't. I'd rather have couple of pushes on the brakes when regen is low, than wasting battery power on preheat.
So if lower re-gen doesnt bother you, dont even worry about cold weather issue
 
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ajdelange

Active Member
Dec 10, 2018
1,077
540
Virginia/Quebec
I don't. I'd rather have couple of pushes on the brakes when regen is low, than wasting battery power on preheat.

Sometimes I find myself thinking like that. It stems in part from residual range anxiety. If I'm staying in a small towm with no practical charging opportunity and getting to the next available charger will leave me with a predicted 10% charge then I would certainly skip pre heat the morning of departure (unless it was all down hill to the next charger). But if I am on an errand near home? Why not. Sure it's going to ost me a bit in terms of more on the electric bill but that's pennies and mitigated by solar panels (not that they do much mitigating at the time of year when you need pre-heat). Sometimes we have to stop and think about what we are thinking.

Where I spend my winters temperatures seldom go below freezing for very long and it takes surprisingly little energy to pre-warm the cabin. Things may be different in Yellowknife.
 

ElectricOrgan

Member
Oct 11, 2019
131
-29
USA
There is no fundamental reason that this scheme could not be used with the induction motors of the pre-Raven design or with the induction motor of the Raven as no current goes to the motor. Redesign of the control system (the bit that sends the gating signals to the transistors) would be required. And I think they are using silicon carbide transistors in the later cars.

It's not the motors that this heating method depend on. It's the driver circuitry for the coils. You said it yourself, they turn on the driver transistors half way rather than fully. In a motor drive circuit there is no reason to turn on a driver part way since this "wastes" power and makes heat which is the opposite goal of a driver circuit. So in the model 3 they made a design decision to add this capability. It is very likely not available in the driver boards for the models S and X. Besides, why bother with that when the car already includes a heater for the batteries? It is a trivial savings in hardware.
 

ElectricOrgan

Member
Oct 11, 2019
131
-29
USA
Someone in another thread talked about not charging before you leave in the morning, rather, charging when you get home in really cold weather. This was to charge the battery when it is warmest to prolong its life. This assumes the car doesn't warm the battery when it is plugged in before charging.

I know the charging rate must be reduced when the battery is cold. I don't know what the car does if well below acceptable temperatures for charging. Does it warm the battery first? Does it limit the charge rate to a trickle?

One thing to be aware of, if you are on a trip, the charge rate can be severely reduced if the battery is cold. They say it will heat up if the car knows it is headed for a charger. But the only way to tell it that seems to be to set the charger as your destination. I've entered destinations where I would only have 5% remaining and it didn't even suggest that I stop and charge. In that case it would not warm the battery on route. Teslas are strange and very unpredictable.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,432
7,642
Boise, ID
Someone in another thread talked about not charging before you leave in the morning, rather, charging when you get home in really cold weather.
Yes, I've heard that suggestion, and it's got some merit but not for the reason you suggest:
This was to charge the battery when it is warmest to prolong its life.
It's not to prolong its life.
This assumes the car doesn't warm the battery when it is plugged in before charging.
...which is false. That's why this isn't about prolonging its life. The battery management system absolutely track carefully when it can charge and how fast based on how cold the internal battery temperature is, and it will warm it up to make sure it only charges at a level that is safe for its temperature.
The real purpose for charging right when you get home is because of that factor. The battery is already warm when you get home. You can have it charge while it is already warm, and the car won't need to run any battery heating. Otherwise, if you get home, and leave the car to sit for the next 5+ hours and get cold before its charging cycle, then it has to waste energy to run battery heating to get it up to a good level to do your charging. It's simply about not wasting energy if you can just get it charged while its already hot from driving instead of letting it get cold and have to re-heat it.

I know the charging rate must be reduced when the battery is cold. I don't know what the car does if well below acceptable temperatures for charging. Does it warm the battery first? Does it limit the charge rate to a trickle?
For those last two questions, Yes. & Yes.
There is a level of coldness where it absolutely won't charge. It would be severely damaging, so the car just prevents it when it is that cold--period. So, it must run battery heating to get the battery pack warm enough to safely start any charging at all. But that is not an instant crossover point from nothing to fast charging. It is a gradual scaling up with temperature. So once it gets warm enough to start, it will start with a low safe level of current while continuing to run the battery heating, using that incoming power from the charge cable. So between the battery heater and the act of charging itself creating a little heat in the cells, it continues to get warmer and keep increasing the charging current.

One thing to be aware of, if you are on a trip, the charge rate can be severely reduced if the battery is cold. They say it will heat up if the car knows it is headed for a charger. But the only way to tell it that seems to be to set the charger as your destination. I've entered destinations where I would only have 5% remaining and it didn't even suggest that I stop and charge. In that case it would not warm the battery on route. Teslas are strange and very unpredictable.
I've gotten awful recommendations from the car Nav like that if I let it choose Superchargers for me, so I just don't. It seems to have a parameter set to prefer the least amount of stops, and it will do ridiculous things like extremely long charge times and tiny arrival % to try to skip over Superchargers to meet that criteria. It sucks. So I just pick the next Supercharger a reasonable distance along the route, that can have a normal arrival % like 15 or 20, and that works pretty well.
 

Skotty

2014 S P85 | 2020 3 P19"
Jun 27, 2013
2,470
1,781
Kansas City, MO
Only one thing is critical on battery temp question -- supercharging. This may be less an issue now with the pre-heating that Tesla has supposedly implemented as a supercharging improvement, but the only real issue is if you try to supercharge on a cold battery, in which case the charge rate will be severely reduced. Typical example: I have to park overnight periodicailly for work without charging; on really cold nights, if I supercharge the next morning, the charge rate starts at like 10 kW and climbs super slowly, never making it above 60 kW, instead of starting at closer to 120 kW and dropping slowly. Makes a huge difference in time to charge.
 
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Reactions: Rocky_H
Nov 7, 2019
41
-1
Pennsylvania
I've gotten awful recommendations from the car Nav like that if I let it choose Superchargers for me, so I just don't. It seems to have a parameter set to prefer the least amount of stops, and it will do ridiculous things like extremely long charge times and tiny arrival % to try to skip over Superchargers to meet that criteria. It sucks. So I just pick the next Supercharger a reasonable distance along the route, that can have a normal arrival % like 15 or 20, and that works pretty well.

My experience has been the opposite. On trips the car wants to stop more often to keep the charging in the "sweet range" to minimize actual time at the charger. Personally I prefer to run down until I can stop to charge while I eat which means up to 90%. Sitting in the car waiting for it to charge is such a waste of time. I'm going to be doing that before too long. They are finally finishing the Superchargers in Frederick and I will be charging there with nothing much to do. Even though it is in a mall parking lot, the food nearby isn't anything I like and the mall isn't my thing either. Likely I'll only hit that charger for 10 or 15 minutes so I can reach a charger that gets me the rest of the way on my trip.
 

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