Battery Heating May Have Changed

[Kalud]

-14C, unplugged, total draw 10.64 kW.

4.5kW Battery heater
~6.0 kW cabin PTC heater on max
balance is offset to 12V system amps drawn (cabin fan, powertrain coolant pump at 100%)

 

[Doug_G]

Yep. The clear conclusion is that the battery heating has NOT changed.

 

[Andyw2100]

Yep. The clear conclusion is that the battery heating has NOT changed.

I did say "May Have" in the thread title.

I started the thread because as others have confirmed, the API is not returning the correct "Battery Heater On" status in many situations. Believing that the data the API was reporting was correct was my mistake.

 

[Doug_G]

Glad to help.

 

[AWDtsla]

4.5kW Battery heater

5.5kW, it's stamped on the part.

 

[Kalud]

5.5kW, it's stamped on the part.

The sticker says 450VDC / 5556W / 12.3A (car is 403.2V at most fully charged, depends on battery config, 60/70/75/85/90/100 kWh).

I do have root on my car and about once in a while I start manually only the battery heater by preconditioning the pack only and monitoring the current drawn from the wall, always about 4.5kW.

I normally charge at 90% which gives me a pack voltage of 392.09V.

Some maths, 5556W / 12.3A means an internal resistance of 36.72 ohms. So at 90% SOC on my car I get VAPI_batteryVoltage=392.090V so if purely resistive and just ON or OFF, I would draw 4186W. Meaning about 300W left for the two powertrain pumps running at 100%, I don't have the spec of those pumps but that makes sense.

I can redo the test at a lower SOC% hence lower battery voltage to compare.

 

[Andyw2100]

I do have root on my car and about once in a while I start manually only the battery heater by preconditioning the pack only and monitoring the current drawn from the wall, always about 4.5kW.

Just trying to make sure I have this right...

With root access you can preheat the traction pack without preheating the cabin?

Thanks!

 

[Kalud]

Just trying to make sure I have this right...

With root access you can preheat the traction pack without preheating the cabin?

Thanks!

Yes. There is a variable called GUI_schedulePreconditionPackRequest.

 

[Andyw2100]

Yes. There is a variable called GUI_schedulePreconditionPackRequest.

Thanks.

If Tesla doesn't provide the ability to heat the pack via the app with the coming update, I may start looking into what it would take for me to obtain root access. I fear, though, that it will be beyond my capabilities. I was worried enough about rooting my phone!

 

[Nietschy]

Those targets are valid for normal >50% SOC. Its get progressively more aggressive (targets raises) as SOC go down. That's why, even in range mode in cold temperature, at low SOC (like less than 10%) the pack heater turns on with a target around 15C or more.

I do not understand this behaviour.
May you elaborate why this is happening?

I thought that the car tries to conserve energy when the SOC goes down and not up!
If the pack target temp goes up and the car heats the pack more, you would be stranded earlier than later of the car is just sitting around for some time in cold weather. (f.e. at an airport with no charger for 3 weeks)

 

[scaesare]

There's undoubtedly a curve where the energy you can get out of a Li-ion cell by keeping it warm is greater than the amount of energy lost in order to heat it.