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Discussion Starter · #1 ·
Hello, everybody.
I don't think this topic has been discussed well. If it did, my apologies, please help me find the link.

Hats off to Lars for this great explanation on the Tesla thermal management - Using Tesla thermal management system parts - EVcreate
There's a touch of this topic on the AC control, too Tesla A/C Compressor Questions

But I'm hoping to get some insight on how the AC zones are controlled on the EV. This applies to having different cabin zones where, for example, a passenger gets to control her\his temp independent of the driver. But it also applies to the fact that when batteries are actively cooled the cabin temperature is controlled independently.

When only battery or only cabin cooling is needed, it makes sense that a respective control solenoid (on/off) will either direct refrigerant to the chiller or the evaporator. But what happens when both are needed at different temperatures?

Rectangle Font Parallel Pattern Design


The way I can think it works is that the heater core in the HVAC or the battery heater will add heat to adjust the cabin or battery temp. respectively. Seems inefficient, though.

Please help me figure it out.
 

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Two independent heaters in different loops for battery and cabin. Resistors are very efficient at turning electricity into heat and work at very low temperatures, whereas heat pumps don't. Tesla is allegedly under investigation in Canada after Model 3 heat pump owners complained about poor heating in witch's t1t temperatures.

Mixing and directional doors via actuators in cabin give the Mistress warmer temperatures on her side of the car.
 

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Discussion Starter · #3 ·
Two independent heaters in different loops for battery and cabin. Resistors are very efficient at turning electricity into heat and work at very low temperatures, whereas heat pumps don't. Tesla is allegedly under investigation in Canada after Model 3 heat pump owners complained about poor heating in witch's t1t temperatures.

Mixing and directional doors via actuators in cabin give the Mistress warmer temperatures on her side of the car.
If I understood correctly, let's walk through a simple example....
If I want the battery to be cooled down to 20C and the cabin to be cooled down to 25C. I would open both valves #8 and #9, run the compressor until the battery temp sensor (#6) is as 20C, and meantime using the heater core on the evaporator #9 bring the cabin temperature to 25C?

Also, does this make sense how additional "zones" would be added to the same compressor setup?
Rectangle Font Parallel Slope Diagram
 

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i would recommend using a heatpump window unit or RV unit. with mine i have my evaporator coil in a reservoir with the liquid it is submerged in being pumped to all the different components along with the heater core. the primary reason i did this is so the motor can actually heat the car when it is cold by pumping the reservoir fluid through it basically giving free heat to the batteries and interior.
 

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Keep it a neat install, though...something like this as an idea:
View attachment 128892
Mine is a LOT more elegant than that. I gutted my window unit apart so I can have the compressor and coils where I wanted them to be along with not having any of the plastic trim. I also gutted all the original electronic controls and opted for cheap contactors with rely switches.
 

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Discussion Starter · #8 ·
i would recommend using a heatpump window unit or RV unit. with mine i have my evaporator coil in a reservoir with the liquid it is submerged in being pumped to all the different components along with the heater core. the primary reason i did this is so the motor can actually heat the car when it is cold by pumping the reservoir fluid through it basically giving free heat to the batteries and interior.
That's 120vac system. Wouldn't be inefficient on the 400vdc pack?
 

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Discussion Starter · #10 ·
It would if you don't have a nice inverter. If you don't already plan on using a high end inverter you probably want to use a RV unit. They are very similar in size and you can find some that run on DC current.
Do you have an example of such unit?

Did you also split the refrigerant loop and added the heat exchanged to use the unit for cooling the batteries?
 

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Do you have an example of such unit?

Did you also split the refrigerant loop and added the heat exchanged to use the unit for cooling the batteries?

yes the batteries run though the heatpump. i also run the motor through it when it is being used to heat the car since that is basically free heat.
 

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Discussion Starter · #12 ·

yes the batteries run though the heatpump. i also run the motor through it when it is being used to heat the car since that is basically free heat.
Interesting....could you please post some pictures and diagrams of your setup. Eager to check it out.
 

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Interesting....could you please post some pictures and diagrams of your setup. Eager to check it out.
To be completely honest, I really don't want to pull apart my dash again. Also mine uses a window unit with the compressor under the hood, evaporator under the dash, and coil right behind the front bumper. I used to work in HVAC so none of this is really new to me as far as residential units go. Main reason I prefer them over a car unit is that I have little experience with automotive AC units and don't want to test my luck.
 
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