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Battery heating while preconditioning cabin

jalatontarzan

Member
Oct 27, 2019
17
33
Finland
Can anyone confirm the behaviour of cabin/battery heating that happens in my model 3? Everytime when I start cabin heater from app the battery heater kicks in and motors pull the 7kw like they do when heating battery. Checked from scanmytesla and total battery draw can be as high as 14kw. 7kw for the motors, 6kw for cabin heater and rest for seat heaters, computers and so on. It doesn't matter if charging or not, so not even 11kw charger is able to top that and range loss before driving is very fast and noticeably.

When I was testing temperature was +10C and cell temperature was +20C, so seems like totally unnecessary and wasted energy. It also really adds the total energy consumption, especially when driving short trips at winter times. 15min of heating can now consume as much as 3.5kwh, which alone is about 20km worth of range. Now lets say you drive 10km with 200wh/km, total energy consumption is now 550wh/km! Range loss before drive could also be a problem if already stretching close to the maximum range at cold weather.

Imo this should be behind an option, and if it was, it would be a great thing to have a manual battery heater available. But is this just a fluke with my car and should I contact service center or can anyone else confirm? My solution now is to not preheat if I don't absolutely have to (frozen windows for example). I hate wasting energy so much that it nearly doubles or triples the consumption compared to only driving. Also don't like that something so fundamental basic function of the car changes without notice.
 
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Tam

Well-Known Member
Nov 25, 2012
8,804
7,615
Visalia, CA
...manual battery heater...

To preheat your main battery, you can use your app and preheat the cabin. It's not a guaranty that if the cabin is preheated, your main battery will too because it's automatic and it does not need to comply with what we want.

However, you know that your preheat action does activate your battery heating when you see the snowflake icon on your HVAC app on your phone. If there's no snowflake icon, that means only your cabin is heated and not your main battery.
 

GtiMart

Member
Nov 13, 2019
871
701
Quebec City, Canada
Your are correct. Target active heat temp varies I think but 20C is a normal target. It should stop heating the battery around that. Yes, it pulls a lot of power. Keeping the car in a garage certainly helps.
I believe the dog mode and camping mode don't actively heat the battery but these are only available in the car UI.
Heating the battery will give back regen and some lost power when it's really cold. I agree with you that for short trips it's not worth it. I would also like options but that makes it more complicated for "normal people" to have a Tesla. I assume that's why they are not exposing such information and options
 

GtiMart

Member
Nov 13, 2019
871
701
Quebec City, Canada
You're right UncleCreepy. I was replying to the OP and somehow didn't see that post. The snowflake indicates a cold enough battery that some range kWh portion is unavailable until it heats up. Obviously in that situation the battery needs heating but the target battery temp is higher than the snowflake appearance temperature.

Battery heating is dictated by software and Tesla could decide to change the behavior eventually, yes.
 

Tam

Well-Known Member
Nov 25, 2012
8,804
7,615
Visalia, CA
That's not correct. My M3 preheats the battery even without the snowflake symbol present when I turn on the heat via the app.

Below is from the manual:

"Blue Snowflake Icon
A blue snowflake icon appears on your touchscreen when some of the stored energy in the Battery may not be available due to cold
Battery temperature. This portion of unavailable energy displays in blue on the Battery meter. Regenerative braking, acceleration, and charging rates may be limited. The snowflake icon no longer displays when the Battery is sufficiently warmed."

The picture below is with the snowflake which means the battery is being warmed:

b5yuhi4qkw601.png



The picture below is without the snowflake which means the battery is not being warmed even though the (red hot arrow) climate control is on:

7add3b21-a7b6-406c-aa6d-bcb142d1564f-png.351103
 

ZOMGVTEK

Member
May 19, 2015
559
434
'Merica
The fact that they’re preheating the battery so readily now, leads me to assume they have both confidence in the motor design enough that it can tolerate the abuse, and they feel it’s advantageous enough for the battery to warm it although it adds discharge cycles.
 

jalatontarzan

Member
Oct 27, 2019
17
33
Finland
The fact that they’re preheating the battery so readily now, leads me to assume they have both confidence in the motor design enough that it can tolerate the abuse, and they feel it’s advantageous enough for the battery to warm it although it adds discharge cycles.
Motors can definitely handle the heat load of couple kw and warmer battery is also of course beneficial for the battery health and user experience. I would still like to know the reasons for this half forced heating, because the car still lets me drive with cold battery if I simply don't preheat the cabin. With limited power and regen available of course, but cold battery doesn't seem to be too big concern to Tesla because it doesn't force the heating while driving unless navigating to supercharger, which is understandable.

Now its kind of hidden of energy loss. I think people would complain a lot more if it would happen during driving and seeing 2-3x consumption in trip meter. It's also problematic because Tesla markets these cars as enviromentally friendly and cheaper to run compared to gas cars. Wasted energy really adds up your co2 emissions, of course depending how your electricity is produced but even with renewables or nuclear it's not a good thing to consume excessive amounts of energy for nothing. Now my car is also more expensive to run than my old gas car if preheating and driving short trips of about 10-20km depending of temperature.

Keeping it simple is a better way than making it overcomplicated, but hiding the information is annoying. This definitely didn't happen last winter. I guess back then it was annoying to not have a way to heat the battery :D
 

taraquin

Member
Jul 14, 2013
217
110
Norway
TM3 does not show the battery-heater icon. Only TMS and TMX does this when the battery heater element is active. On TM3\Y I have never seen that icon even though motor(S) are running to heat the battery.

As for powerdraw, it only draws up to 14kW for a short time. The most I have seen climate alone draw over time is 3kW. For the RWD it seems like 3.5-4kW is the max powerdraw from motor heating battery. I have a 11kW charger at home and on my SR+ it always charges and battery percentage does not drop even in the first minutes after preheating since the max possible powerdraw is around 10-11kW in my car.

The reason why it heats the battery to 26C (according to Teslabjorns scan my Tesla results) is to gain good charge speed at SC, but that takes a lot of time to achieve. At 0C it took him close to an hour if I remember correct. If you don`t want the battery to be heat, just heat it for 5-10 mins, that should clear of any snow\ice and get the battery a few degrees warmer. It continues to heat up after driving aswell since the coolant is now warmer than ambient temp. This morning it was -1C outside. I preheated the car for 20mins and battery went from 43 (38% with frost icon) to 37%, meaning preheating used 3kW on my SR+. I got a bit over half regen. 1\3 regen is more than enough for me so I could have preheated only for 10 mins.

A thing that is interesting regaring regen\soc is that the battery allows for far more regen\charging if SOC is low. I get much more regen at same temp at 30% soc than 60% soc. This means that if soc is low, shorter prehating to get good regen\chargespeed is required vs high soc.
 

jalatontarzan

Member
Oct 27, 2019
17
33
Finland
TM3 does not show the battery-heater icon. Only TMS and TMX does this when the battery heater element is active. On TM3\Y I have never seen that icon even though motor(S) are running to heat the battery.

As for powerdraw, it only draws up to 14kW for a short time. The most I have seen climate alone draw over time is 3kW. For the RWD it seems like 3.5-4kW is the max powerdraw from motor heating battery. I have a 11kW charger at home and on my SR+ it always charges and battery percentage does not drop even in the first minutes after preheating since the max possible powerdraw is around 10-11kW in my car.

The reason why it heats the battery to 26C (according to Teslabjorns scan my Tesla results) is to gain good charge speed at SC, but that takes a lot of time to achieve. At 0C it took him close to an hour if I remember correct. If you don`t want the battery to be heat, just heat it for 5-10 mins, that should clear of any snow\ice and get the battery a few degrees warmer. It continues to heat up after driving aswell since the coolant is now warmer than ambient temp. This morning it was -1C outside. I preheated the car for 20mins and battery went from 43 (38% with frost icon) to 37%, meaning preheating used 3kW on my SR+. I got a bit over half regen. 1\3 regen is more than enough for me so I could have preheated only for 10 mins.

A thing that is interesting regaring regen\soc is that the battery allows for far more regen\charging if SOC is low. I get much more regen at same temp at 30% soc than 60% soc. This means that if soc is low, shorter prehating to get good regen\chargespeed is required vs high soc.
Dual motor models draw twice the power for battery heating due to having two motors heating. It's true that when temperature is mild enough 5-10min of preheating is sufficient, but when temperatures get -10C to -30C, it might take over 15min to defrost the windows with full power from cabin heater (combined with battery heating total energy consumption is 14kw) which means quite significant range loss without getting any major benefits from few degrees warmer battery. I have only 3,6kw charger so negative battery draw is huge and can take almost as much power as driving 80kmh. Without charging at the same time power consumption is almost equal to driving 100kmh which is just insane. 11kw would help a lot, but even then net draw can be negative with dual motor models. And huge energy losses add costs and enviromental impact nevertheless.

And yes, regen is affected by temperature and SOC. Regen is just like charging and at higher % there just isn't room in the battery for high power inputs. Cold temperatures just lower the charging/regen curve and cuts it to zero after certain temperature. If you want to have any significant regen in colder temperatures better to have also low SOC. Lower the better. But any regen benefits are neglected by huge power consumption before the drive unless you are driving like maniac from full blast to full regen every time possible. Using no regen as long as not using brakes is most efficient driving anyway.
 

taraquin

Member
Jul 14, 2013
217
110
Norway
Jalatontarzan: If at home you can preheat the car by opening one door slightly and turning on climate. No battery heating, only cabin then.

Also try setting fan at 1 or 2, point to windows only and turn off ac if weather is dry. This reduced consumption while driving a lot while still maintaining temp and no fog at front windows even in a few degrees below zero.
 

rrolsbe

Member
Feb 18, 2017
223
126
Albuquerque
Sit something heavy in the drivers seat. Last time I checked. the car will not heat the battery if if thinks the driver is sitting in the car while preheating the cabin. I do not know what would happen if the weight was placed in the front passenger seat, worth a quick test.
 
Last edited:
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rrolsbe

Member
Feb 18, 2017
223
126
Albuquerque
Sit something heavy in the drivers seat. Last time I checked. the car will not heat the battery if if thinks the driver is sitting in the car while preheating the cabin. I do not know what would happen if the weight was placed in the front passenger seat, worth a quick test.
You would also need to verify the car will enter sleep state, when it thinks someone is sitting in the drivers seat, if you put the weight on the seat the night before.
 

GtiMart

Member
Nov 13, 2019
871
701
Quebec City, Canada
You know, that nice icon in the app that exists for the S and X... It would be great if it could also be shown for models 3 and Y, and be a button you can click to control it. Unfortunately that service isn't available in the API, Tesla would need to add it. IMO, it shows that Tesla is definitively a Californian company. I think they need to start investing more time in research in cold climates. After all, they want to sell worldwide. This heating as well as some tweaks to the stability/traction programs are required in cold climates.
 

UncleCreepy

Member
Mar 29, 2020
219
347
Lunenburg, ON
Below is from the manual:

[...]
That's the Model S manual. Things might be different in the Model S. I can only speak for the Model 3.

This morning we had slightly above freezing temperatures. There was no snowflake symbol though. I set the temperature to 20 °C (I believe that's 68 F) and went to the car. Model 3 does not have a battery heater, instead it uses the motors to produce heat and transfers it to the battery. I could clearly hear the pumps running, so the car was heating the battery although there was no snowflake symbol. I also saw that it drew the full 48 Amps from the charger although it wasn't actually charging. The display showed "Charging Complete". Since the cabin heater can only draw 6 kW or so, this further shows that the car was also heating the battery.

In light of what you wrote I take it back. You probably weren't wrong. We were just talking about different cars.
 

UncleCreepy

Member
Mar 29, 2020
219
347
Lunenburg, ON
They apply direct current to the motors which won't make them spin but it generates heat. The water cooling system then transfers this heat to the battery. Mind you, we are in the Model 3 forum here. The other models may use other means of heating the battery.
 

taraquin

Member
Jul 14, 2013
217
110
Norway
They apply direct current to the motors which won't make them spin but it generates heat. The water cooling system then transfers this heat to the battery. Mind you, we are in the Model 3 forum here. The other models may use other means of heating the battery.
No to be a prick, but it?s coolant which stays liquid far below freezing :)

TMS\TMX has a dedicated heater which can use 3 or 6kW to heat battery. In TM3 each motor generates 3,5-4kW of waste heat to warm coolant and then battery. On the RWD-models it seems a maximum of 3,5-4kW is used. 7-7.5kW on dual motor. Heating takes a bit longer than on TMS\TMX, but the motor and other components are also heated which reduces resistance due to the cold, on TMS\TMX only the battery is heated and the coolant is indirectly heated.
 
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theothertom

Member
May 9, 2020
313
203
South Carolina
They apply direct current to the motors which won't make them spin but it generates heat. The water cooling system then transfers this heat to the battery. Mind you, we are in the Model 3 forum here. The other models may use other means of heating the battery.
Cool. So the motor windings act as "strip heaters" when DC is applied. Thanks.
 

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