In the first post about the battery thermal management I discussed the importance of keeping batteries in their ideal temperature range. Now let’s look at how Tesla approaches this. I will explain the various components of the Tesla thermal management system and where possible offer relevant connectors and information so you can use Tesla components in your electric car conversion project.
As discussed in the temperature blogpost cooling or heating an electric car battery is possible using air or liquid. Tesla has adopted the liquid cooling approach.
System layout overview
Below is a simplified sketch of the cooling system in a Tesla Model S. I omitted The DC/DC converter and the chargers and some other details.
1. Tesla battery modules cooling/heating
Each battery module in a Tesla Model S and Model X battery pack has a thin aluminum tube in between the 18650 cells. The P100 modules even have two tubes for enabling cross flow. Therefore, the heat exchange in those modules is even better. A 13 mm internal diameter tube running along each side of the battery pack has 8 mm branches with corrugated tube connecting all battery modules in parallel. In other words, all modules are receiving coolant of similar temperature. Connecting them in series would result in an uneven temperature distributing since the first modules are in favor. In addition, it results in a big pressure drop.
Tesla uses quick connect fittings with manual lock on the battery modules. NB. The 6,3 kW modules from a Tesla Model S P100D use different coolant connectors. These are available on request.
2. Tesla battery heater
Once source of heat for the battery is an electric battery heater running from the high voltage battery pack. This is a sheath heater with a capacity of approximately 5 kW. You can find two different types in the Tesla Model S. Early models (2013 and 2014) had one from Philips & Temro Zerostart. I believe these are prone to failure and can result in isolation errors. Therefore, from modelyear 2015 onwards Tesla switched to a heater made by LG. You can recognize these by the black plastic back cover. The Tesla part numbers I managed to track down over the various model years are:
- 1009508-00-E (2013) Philips & Temro Zerostart
- 1028689-00-B (2014) Philips & Temro Zerostart
- 1038901-00-E (2015) LG
- 1038901-00-F (2015) LG
- 1038901-00-G (2015, 2016, 2017) LG
- 1038901-00-H (2017) LG
- 1038901-00-I (2018) No longer has the LG logo but appears to be the same unit. Made by Tesla?
- 1038901-00-J (2018, 2019) Also Tesla sticker, no LG logo
The model year indicates in what year a letter was first used. All heaters have the same form factor. The front high voltage junction box (FHVJB) (Tesla part number 1028843-00-B or 1028843-00-C) controls the battery heater and can reduce heating power/capacity via high voltage PWM.
The battery heater has a build in thermistor. It is an NTC thermistor. I measured the resistance at various temperatures and calculated the thermistor values. It is a 10K thermistor with a β of 5500 K.
In addition, heat can come from the motor/inverter. In that case, waste heat from the drivetrain is used to heat the batteries. The system goes from two separate parallel loops into a series layout using the 4-way valve.
3. The 4-way valve
The 4-way valve (Tesla part number 6007370-00-B) can join or separate the batteries coolant loop from the rest. In other words, if the battery temperature is below the ideal operating range the 4-way valve will join the two circuits. Similarly, as soon as the batteries have reached their ideal operating temperature range the valve will separate the two. In that configuration the radiator is available to cool the drivetrain. Therefore, if the battery needs to be cooled, the active cooling using the airconditioning kicks in and the chiller is used.
The valve has three positions of which Tesla uses two.
- Input = GND
- Feedback ≈ 9,6 V
- Input = 12V+
- Feedback ≈ 2,3 V
- Input = Not connected
- Feedback ≈ 6 V
First I’ll explain the 3-way valve and then I’ll get back to the input and feedback below in “Wiring the 3-way and 4-way valve” since this is the same for both valves.
4. The 3-way valve
Tesla used two 3-way valves. In the Model S the part number is 6007384-00-B and in the Model X the part number is 1064225-00-C. These 3-way valves are used as bypass for respectively the radiator and the chiller.
In addition, in mixing mode, you can use it to divert the output of a (battery) fluid heater to both the battery and a fluid interior heater.
Also the three way valve has three positions. It has the same actuator and form factor with one outlet less, even the outlet numbering is consistent. The valve flap / ball is different though.
- Input = GND
- Feedback ≈ 9,6 V
- Input = 12V+
- Feedback ≈ 2,3 V
- Input = Not connected
- Feedback ≈ 6 V
‘Bypass’ and ‘include’ are arbitrary. I’m not sure how Tesla exactly uses them and you can choose whatever is convenient in your build. Next question is: “How do we use and control these valves?” This is explained below in ‘wiring the 3-way and 4-way valve.
Wiring the 3-way and 4-way valve
Using the 3-way and 4-way valve in your project requires a small control system. The valve has four contact pins.
You need to provide the input pin with a signal (GND, 12V or NC) en then the feedback will show the indicated voltage as soon as the position is reached.
Currently I am working on developing a Tesla valve and pump controller. It will have some simple inputs either via CAN-BUS or analog to control these valve positions. It will also have a feature to control the below Tesla pump.
5. Water pump
Depending on the model year, Tesla used two or three electric water pumps in their cooling circuit. At least early models had a backup pump in the battery cooling loop. Once the 4-way valve separates the batteries loop from the rest, each loop has it’s own dedicated pump. I have seen various water pumps in the Tesla Model S and I am not sure which pump type / part number is used where exactly. The below information is for the 6007367-00-E and probably also applies to at least 6007367-00-*, 6008047-00-* and 6007373-00-*. Not tested yet myself so curious to hear your findings if you did. Full Tesla water pump parts number overview in “Connector kit water pump Tesla Model S / Model X“.
The pump has four inputs: 12V+, GND a PWM input for speed control and a PWM output for diagnostics. Both the pump and the mating connector are available at EVcreate.
Specs of the Tesla water pump
The nominal voltage is 13V (accepts 8V – 16V) and the maximum amp draw is around 7 A. In my view quite significant, so reducing pumping power via PWM if less flow is needed can be very beneficial. The fluid connections are 19 mm barb hose. Pump speed is 750 to 4700 RPM.
Mounting the Tesla water pump
The pump must be installed in such way that air cannot get trapped inside. In addition it is important that the pump is positioned low enough since it is gravity fed and not self sucking. This applies to most electrical (auxiliary) water pumps.
Not allowed orientation
Furthermore it is important to install the hoses in a way they to not create an axial load on the pump.
Wiring the Tesla water pump
The pump has four connections. Our Connector kit water pump Tesla Model S / Model X contains the mating connector, seals and terminals.
Controlling the Tesla water pump
Via pin 3 (see above) you can control the speed of the pump. It requires a switched to ground PWM signal. Not all inputs are valid. See below table and graph for the correlation. The normal operating range is defined by the following formula RPM = 68,8 x PWM – 550.
|0 – 8||Invalid input|
|8 – 12||0|
|13 – 17||Invalid input|
|18 – 20||750|
|21 – 79||(65,8 x PWM – 550)|
|80 – 82||4700|
|83 – 100||Invalid input|
If you do not provide a normal input after a short startup and diagnostics time (4 to 7 seconds) the pump will start running at full speed.
7. Airconditioning compressor
Tesla used a couple of different AC compressors. Early models (modelyear 2013 / 2014) used an ES34C by Denso and has part number 6007380-00-D. This one is PWM controlled.
Connect 12V + in to pin 8 and provide chassis ground to pin 1. Pin 4 and 8 are not connected (don’t even have a male terminal in the compressor connector). You can leave the power feedback (pin 5) and diagnostics (pin 3) unconnected too.
The compressor is enabled by grouding pin 2 (active low) and speed control via a PWM signal on pin 6.
|4 =||Not connected|
|5 =||Power feedback|
|6 =||PWM in|
|7 =||12V in|
|8 =||Not connected|
Later models (CAN control unknown)
Later models (2015/2016) had a HVCC ESC33 and Tesla part number 1028398-00-E, 1028398-00-F and 1028398-00-J. Tesla also used the Hanon HES33 and is found with number 1063369-00-D, 1063369-00-E, 1063369-00-F and 1063369-00-G. Both later types are unfortunately CAN controlled and details unfortunately are unknown (so far).
I have adopted another approach and use a more lightweight Benling AC compressor. More details can be found in a separate blogpost.
8. Tesla chiller (battery heat exchanger)
Over the years Tesla used three different types of chillers. To be exact, they used three different block valves on the heat exchanger by Modine. The exchanger itself is also found with different part numbers:
|Type||Block valve part number||Heat exchanger part number|
|Block valve part number is leading||Examples, not an extensive list|
|TXV without solenoid||1019541-00-B||Modine = 1E006836|
Tesla = 1019540-00-C
|TXV with solenoid||6007362-00-C||Modine = 1E006773|
Tesla = 1007476-00-D
|EXV||1039040-00-C||Tesla = 1037764-00-C|
Tesla = 1037357-00-D
Modine = 1E007303
The EXV is the latest generation of expansion valves. It uses a control loop with a sensor that provides the right amount of refrigerant for the chiller. However, that requires a separate sensor and ECU. Above all, the control specs are unknown.
The TXV stands for Thermostatic Expansion Valve. Using the temperature it allows more or less refrigerant through. The TXV with solenoid is the most easiest DIY approach. You can just use the solenoid to allow the chiller to cool or not.
However, there are many Tesla’s, in particular early ones using the TXV without solenoid. My theory is that this works fine as long as you bypass the chiller in case no active cooling is needed (any input on this is welcome). Then there will be no cooling effect in the block valve and as a result it closes or even freezes. It is important though to not run the AC compressor when both the chiller and cabin are not requiring cooling. I will elaborate on this in a separate airconditioning topic.
Barb hose internal diameter that fits the coolant inlet/outlet is 19mm.
The valve is normally closed. While powering the solenoid with 12V (polarity does not matter) it opens. I did a test and at 13,6 it draws 600 mA. You could consider using an economiser, for example the Texas Instruments DRV103.
9. Tesla cabin (evaporator) expansion valve
The cabin evaporator has a block valve / expansion valve with an integrated solenoid. In case battery cooling is required but cabin cooling is not.
In later models Tesla started using the EXV also for the cabin evaporator.
Blog series on battery thermal management
- Ideal battery temperature?
- Using Tesla thermal management parts
- Other OEM thermal management
- Example of DIY approach
- Battery temperature data in practice
Any feedback, additions, suggestions for improvement is welcome. Please contact me by e-mail.
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