# Model 3 thermal system



## Guest (Nov 16, 2017)

I'm eager to see how Model 3 is designed. 
For now, I have some ideas: how Model 3 thermal system might operate.
Model S/X system is fully understood. I did some explaining here:
Tesla Thermal Management System - explanation

We can be sure that Model 3 will have more simple system. For starters, we know that Model 3 does
not have battery heater. Also there is only one condenser and one glycol radiator.
Also it's clear that there is a chiller (AC/glycol heat exchanger). It can be seen here as part "E":
Name That Part!
And when I saw that chiller is right next to expansion tank I Immediately thought that chiller might be for two coolant loops.

I've tried to simplify Model S thermal design and this is what I was able to sketch:








And some scenarios of how things can operate (P is fluid pump, LOW=off HIGH=on(whatever speed)).








Notice that HVAC doesn't have an evaporator, just a coolant radiator. That loop is cooled by heat exchanger. That same loop can also be warmed with drivetrain heat (but only when compressor is not used, which is true for cold weather anyway). Heat exchanger will exchange heat in any direction. Additional efficiency could be gained if coolant bypass did not bypass heat exchanger, just radiator (even though louvres are closed, there is likely considerable heat loss there, depending on the exterior radiator box design).

If Model 3 has evaporator in HVAC and not glycol heat exchanger, then there should be two valves (parts 14 and 15 ModelS explanation), no secondary fluid pump. No cabin heating from drivetrain heat would be possible (only good for long trips when battery is already warm in chilly weather, aka more capable range mode).


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## Sandy (Jun 3, 2017)

Arnis, I’m pretty technical but this is over my head. With no battery heater in the M3 how do you precondition the battery?


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## Guest (Nov 17, 2017)

Anything in the glycol loop that can create/capture/dispose thermal energy can be used to change battery temperature. 
Most capable things in this loop are:
drivetrain (motor/inverter)
heat exchanger (connected to refrigerant loop and HVAC loop).
exterior radiator (if exterior temperature is different from battery temperature).
Theoretically, if HVAC PTC element and radiator are the same thing (this is true for BMW since 2005), heat generated
by PTC element can be transferred to battery pack using heat exchanger.

Though actually, Mr Musk mentioned that battery will get preheating energy from drivetrain. Imagine revving ICE engine
in neutral. It doesn't drive the wheels but burns a lot of juice. Same here. Motor doesn't turn but uses power. 0% efficiency.
It should be possible to generate lots of heat while driving as well. Just reduce drivetrain efficiency from 94% down to,
let's say, 60%. It's like driving on highway with 3rd gear.

Should have added another sketch for "preheating while parked" - write "HIGH" next to drivetrain.

Should add that I hate the likely thing that M3 doesn't come with reversible refrigerant loop like many other EV's do.
Though changing that with this design is piece of cake. 2 valves, some software. Slightly different glycol bypass plumbing.


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## garsh (Apr 4, 2016)

Sandy said:


> Arnis, I'm pretty technical but this is over my head. With no battery heater in the M3 how do you precondition the battery?


In summary, the Model 3 has the motors perform double-duty, and they actually heat the fluid that is used to warm up the batteries.


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## Sandy (Jun 3, 2017)

arnis said:


> Anything in the glycol loop that can create/capture/dispose thermal energy can be used to change battery temperature.
> Most capable things in this loop are:
> drivetrain (motor/inverter)
> heat exchanger (connected to refrigerant loop and HVAC loop).
> ...





garsh said:


> In summary, the Model 3 has the motors perform double-duty, and they actually heat the fluid that is used to warm up the batteries.


Ok, makes sense. Thanks!


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