Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

arnis

Member
Apr 13, 2015
920
597
Estonia
So I would like to explain everything I understand about Model S (very likely Model X is similar) thermal
management system.
Number in yellow is slightly to the left of the object it refers to.
It's easier to open the picture in different window, drag it to the left screen portion while keeping text to the right.

Tesla Thermal Screen.jpg

1. Main coolant radiator. Does not have a fan apparently. When vehicle is in motion air passes through the fins cooling the liquid. Coolant enters from the right side. This radiator can be bypassed with device #10.
2. Coolant circulation mode selector. A device that switches between two modes: Series and Parallel. If series, coolant passes from #1 to #3 and then from B to #7. If is parallel, one loop passes from #1 to #7 and other loop from B to #3.
3. 12V coolant pump. Percents indicate pump running speed. Slower speed consumes less energy, prolongs pump life and slows the coolant flow.
4. Adjustable coolant redirection valve. Sends 100% of coolant from #3 to #5, 100% form #3 to #13 or anything in between.
5. Coolant heater. Apparently is rated for 6kW. Runs on high voltage. If activated, coolant will be heated up. This is used to heat the Battery fast. Heat generated by #6 #8 #9# can also be used to for pack heating. Cold pack will also cool down those devices.
6. DC-DC converter. Takes energy from high voltage pack, keeps 12V battery charged and all 12V devices powered up. Small part of coolant is directed into this device as heat generation is small.
7. 12V coolant pump. This pump is required to keep second loop of coolant flowing if #2 is in parallel mode. Acts as a backup to #3. In series mode both pumps run at equal speed.
8. On-board charger. Is used for vehicle charging. Converts AC grid electricity to suitable DC for main battery. Second charger is not available any more. There is a coolant bypass. Likely required due to single charger has up to half the coolant throughput. Number on the left indicates temperature of the electronics inside.
9. Drivetrain. Coolant enters the motor. Circulates in the stator. Also circulates in inverter (power electronics) and then exits (with temperature value shown). Transmission (reduction gear and differential) doesn't require cooling though it gets some heat as it is between warm motor and inverter. Which raises the temperature of the oil and makes vehicle slightly more efficient. Also rotor temperature is shown (most likely calculated estimation) and Inverter electronics temperature (PCB).
10. Adjustable coolant redirection valve. Same as #4. Either sends 100% of coolant through the radiator, bypasses 100% or anything in between. If coolant is not directed to the radiator it can be used to heat the Battery.
11. AC condenser. Required to cool down refrigerant. Does have a fan. Fan speed indicated in percents. There are two condensers each having a 12V fan. Are between fog lights and front wheel arches. Air enters through louvers and exits to the wheel arc. Louvers can be closed for better drag coefficient.
12. Electric Air Conditioner Compressor. Runs on high voltage. It is used for two purposes. To cool the air for the cabin using #16 and/or to cool the glycol loop using #13. Percents indicate compressor running speed. If cooling requirements are very small compressor will be temporarily stopped to allow cabin air evaporator to stay above freezing point. Sensors before and after indicate temperature and pressure of the refrigerant before and after the compressor.
13. Refrigerant-coolant heat exchanger. Functions the same way as #11 #16 but instead of air it cools glycol coolant passing through it. While #16 is not allowed to get below 0*C/32*F chiller can go colder as coolant will freeze at much lower temperatures. Though it's more efficient to pass as much of coolant as possible. Chiller can be disabled with #14. To keep #16 functional (if user requested) #4 can redirect only some of the coolant.
14. Chiller activation valve. Is an on-off valve that either blocks the refrigerant from expanding into #13 or not.
15. Cabin evaporator activation valve. Is an on-off valve that either blocks the refrigerant from expanding into #16 or not.
16. Cabin air evaporator. Radiator inside HVAC system that cools the air that passes through. If climate control AC setting is "ON" or precooling is activated remotely this will cool and dry the air that passes it. Air gets here through cabin air filter and continues to #17.
17. Cabin air PTC heater element. Apparently is rated for 6kW maximum power. Runs on high voltage. Due to it being Positive Thermal Coefficient device, it can generate 6kW of heat only if air that enters is very cold and is moving very fast. If the element gets hot, it will reduce its draw even if it is activated to 100%. Usually air that exits doesn't get scalding hot no matter what. Temperatures between 55*C - 80*C can be expected at full requested power.

B. Main traction high voltage battery. Some data is shown on the picture.
Trend - Temp - Trend is coolant temperature that enters the battery. If it is hotter, battery will heat up. If is colder, it will cool the pack. Coolant temperature after the pack is to the left, below #7.
Max/Min Cell Temp: extreme values of the sensors in the pack. There are lots of those all mostly being very close to each other.
Passive Cooling Target: this is the value system tries to bring the pack to passively. If B is below this value, heat that has been generated by #6 #8 #9 will bypass #1 and will be absorbed by the B.
Active Cooling Target: this is the upper value for B temperature. If #1 is not capable to cool enough and trend is to go above that value, active cooling measures will increase. This means: #14 activates #13 and #4 selects a portion of coolant to be chilled. Depending on requirements #13 speeds up, as will fans on #11. At some point if cooling is not capable to cope other parameters can be limited (charging speed, vehicle power/regen limits).
Active Heating Target: This is the lower value for B. Anything below that and vehicle will use active measures to heat the pack. Apparently #5. It appears that active heating to that limit can be disabled with range mode. This will compromise battery charging capability/regen a lot and also some of the power output.

There are some more pictures that help to understand Parallel-Series loops and values.
tesla termoregskeem.jpg
 

TonyWilliams

Active Member
Jun 11, 2012
1,438
759
San Diego - Tesla powered Rav4 EV
Some folks have wondered how similar this is to the 2012-2014 Toyota RAV4 EV, and the only significant difference I can find is that the radiator has cooling fans, and the Denso PTC 6kW heating element is a liquid heater for cabin heating... not air.

Also, because this car was a failed marriage between Toyota and Tesla, they have separate heaters / coolant for the cabin heater and the Tesla battery heater (made by a Canadian company that begins with "Sub", but I can't remember the name).
 
  • Like
Reactions: arnis

JZtheHW

Member
May 6, 2018
32
14
Yorba Linda, CA
A great technical explanation, looking forward to the version for Model 3. Is there a parameter or meter measurement when a customer should have their Tesla served for coolant?
 

arnis

Member
Apr 13, 2015
920
597
Estonia
I guess I have to stop telling people there's no oil filters to change on electric cars.
There is an oil filter, but it's there for a decade;)
My estimation is half a decade, but that somebody one day will actually measure oil quality and then we can make clear recommendations.
 

Lucky13

Member
Apr 19, 2018
332
208
San Mateo, CA
Very good stuff. I wonder if the aftermarket is going to step up to the plate and make better cooling for the guys that really want to track these things??
Did not look that complicated
 

ScubaMal

Supporting Member
Supporting Member
May 7, 2018
100
59
Bermuda Dunes, CA
I'm still trying to figure how the Battery Chiller affects the cabin air AC system. I just had mine replaced for hot air in the cabin. Compressor was good.
 

arnis

Member
Apr 13, 2015
920
597
Estonia
I'm still trying to figure how the Battery Chiller affects the cabin air AC system. I just had mine replaced for hot air in the cabin. Compressor was good.
It works on the same compressed system. If chiller leaks, everything is dry and will not operate. Fix the leak and refill. All works again, incl cabin chiller.
 
  • Like
Reactions: MP3Mike

ScubaMal

Supporting Member
Supporting Member
May 7, 2018
100
59
Bermuda Dunes, CA
It works on the same compressed system. If chiller leaks, everything is dry and will not operate. Fix the leak and refill. All works again, incl cabin chiller.
Thanks. But why would the SC tell me that the battery cooling system was still working and only the cabin air was affected. I live in the desert where temps are at over 110 degrees now. I asked the SC if it was OK for the car to sit in the heat while waiting a week and a half for a battery chiller.
 

arnis

Member
Apr 13, 2015
920
597
Estonia
Because battery can also be cooled with coolant (not chilled with AC system) while driving. Coolant can cool down to ambient temperature with coolant radiator. Though SuperCharging would be limited as model S/X do not have a fan for that radiator.
 

ScubaMal

Supporting Member
Supporting Member
May 7, 2018
100
59
Bermuda Dunes, CA
Because battery can also be cooled with coolant (not chilled with AC system) while driving. Coolant can cool down to ambient temperature with coolant radiator. Though SuperCharging would be limited as model S/X do not have a fan for that radiator.
Well that makes sense. Thank you for the explanation. The outside ambient temps are in the 110's but the inside cabin with the windows closed can reach over 150 degrees. So the ambient battery coolant keeps the battery at ambient air temp. Can the batteries handle 120 degrees ambient temperatures without suffering range loss?
 

arnis

Member
Apr 13, 2015
920
597
Estonia
If air is 110F then battery might be 120F (without supercharging).
120F is fine for battery chemistry Tesla uses. Not ok (in long term) for chemistry Nissan uses.
Keeping state of charge at/below 80% in this case makes thing even better.

Like on the screenshot in the first post, system will try to keep battery at/below 52C (125F)
with active cooling (AC compressor used).
 
  • Informative
Reactions: 5_+JqckQttqck

Snowstorm

Active Member
Dec 8, 2016
1,527
1,430
Ontario Canada
How do we see this thermal situation view?
That would be really cool to see, or does Tesla doesn’t want to make it accessible as they would’ve swamped with owners asking questions thinking something is wrong because they don’t understand how things work.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top