Technical question about pre-conditioning and battery temperature

[yogi799]

I am simply curious, how does pre-conditioning work? Very specific questions here, thanks.

1. does it use liquid lines and some heat pump warms up the liquid which is transferred via some lines tucked in closely to the battery packs? Is it some dense and large liquid circuit OR does it use Air to warm up the battery like a space heater?

2. (unrelated to 1) does the battery warm ITSELF up during driving (similarly to ICE)? I mean: is there some chemical reaction that , when being discharged, keeps the battery warm? Or does the car have to waste energy during the whole trip to use another mechanism/circuit (as per 1 above) to keep battery warm?

 

[AAKEE]

1. Model 3 can use the engines to generate heat (change the engines way of working so they generate some extra heat, about 6kW per motor I think). Teslas with the heat pump can use the heat pump also. The heat source can be heat from generated from motors, heat from cabin and outside air.
The battery is liquid warmed/cooled so the heat is transfered by that liquid.

2. The battery heats from usage (charging of discharging. This is due to internal resistance.
How much depends on the speed or charging power.
Cars with hest pump can use this hest to heat the cabin.
Engines/motors generate heat from driving, this heat can be used to heat the battery or the cabin.

 

[GtiMart]

Each motor can go up to 3-3.5kW, for a total of around 6.5kW I believe.

 

[andy.connor.e]

I am simply curious, how does pre-conditioning work? Very specific questions here, thanks.

1. does it use liquid lines and some heat pump warms up the liquid which is transferred via some lines tucked in closely to the battery packs? Is it some dense and large liquid circuit OR does it use Air to warm up the battery like a space heater?

2. (unrelated to 1) does the battery warm ITSELF up during driving (similarly to ICE)? I mean: is there some chemical reaction that , when being discharged, keeps the battery warm? Or does the car have to waste energy during the whole trip to use another mechanism/circuit (as per 1 above) to keep battery warm?

For the model 3, the motors run inefficiently to produce waste heat. You can even hear the increased noise level of accelerating and decelerating.

For #2, yes they keep themselves warm if they have to. Driving does not produce enough waste heat to keep them warm in temps below like 20. That's also why cold weather driving uses so much more.

 

[AAKEE]

For #2, yes they keep themselves warm if they have to. Driving does not produce enough waste heat to keep them warm in temps below like 20. That's also why cold weather driving uses so much more.

The battery will self heat from heat losses even at -20C or lower ambient at highway speeds etc.
Heat pump cars scavenge the ”heat loss heat” to heat the cabin.

When I drive long drives in very cold Wx, the battery temp commutes between 12C and 17C. If the battery is below 17C it will get heated from heat losses until it reaches 17C and after that the heat pump will heat the cabin with that heat until the battery temp is 12C. At low SOC the battery stays self heating (probably to help counteracting the low power from 2170L we saw when it was introduced).

Today I took the car out of the garage (about 10C) at 2 PM so the battery had cooled after the morning charge.
No precondition, the OAT was -8C.
Batt temp was 8.00C

I drove to the neighbour town, 40km’s at a country road/highway with 90/100kph so about 55-60mph.

The batt temp was 10.5C at arrival, I had the heating on at any stop an did some arrends on different positions.
The batt temp was about the same when I started the drive home, and I arrived at home with 12.5C.

I have this screen in front of the steering wheel (all data from Scan My Tesla is sent to teslaloggers server and then catched by my raspberry pie at home).

 

[andy.connor.e]

The battery will self heat from heat losses even at -20C or lower ambient at highway speeds etc.
Heat pump cars scavenge the ”heat loss heat” to heat the cabin.

When I drive long drives in very cold Wx, the battery temp commutes between 12C and 17C. If the battery is below 17C it will get heated from heat losses until it reaches 17C and after that the heat pump will heat the cabin with that heat until the battery temp is 12C. At low SOC the battery stays self heating (probably to help counteracting the low power from 2170L we saw when it was introduced).

Today I took the car out of the garage (about 10C) at 2 PM so the battery had cooled after the morning charge.
No precondition, the OAT was -8C.
Batt temp was 8.00C

I drove to the neighbour town, 40km’s at a country road/highway with 90/100kph so about 55-60mph.

The batt temp was 10.5C at arrival, I had the heating on at any stop an did some arrends on different positions.
The batt temp was about the same when I started the drive home, and I arrived at home with 12.5C.

I have this screen in front of the steering wheel (all data from Scan My Tesla is sent to teslaloggers server and then catched by my raspberry pie at home).

View attachment 887531

That temp number was in °F

just clarify that in the future.

 

[AAKEE]

That temp number was in °F

just clarify that in the future.

Yes, -20C = -4F

 

[andy.connor.e]

Yes, -20C = -4F

I said 20°F

 

[AAKEE]

I said 20°F

Yes, absulotely.

20F is about -7C. At that temp, the battery will easliy increase the temperature by itself and there will be no battery heat on unless starting with a freezing cold battery.

Below todays drive. The garage was slightly less than 10C.
The battery started at 8C and increased to 12.75C during the 40km drive with some arrends and 40km back.
The outer air temperature was -9C (16F) when I left home and for the reminder of the drive around 7C or 20F.

There was no battery heater on, the would have been seen as a selecteble data to view below the graph, se here from another day: If there was preconditioning or battery heater used, they would be found below the graph. No batt heat or precond today. Se below as reference.

 

[andy.connor.e]

I don't have a heat pump 3, but under 20 I sometimes have not been able to get the blue snowflake to go away. I sometimes navigate to a supercharger just to get it above the temp threshold.

 

[GtiMart]

Do you ahve an SR+ / RWD? If so there's only one motor to take heat from... Might explain why your car has more difficulty bringing the battery up to temp...

 

[andy.connor.e]

Do you ahve an SR+ / RWD? If so there's only one motor to take heat from... Might explain why your car has more difficulty bringing the battery up to temp...

LR AWD.

Front motor is generally off on highway

 

[GtiMart]

Yeah, I guess my comment is more applicable when conditioning for supercharging then. You're right, in normal driving the front motor won't play a role unless accelerating reasonably fast or when wheels start slipping.

 

[yogi799]

Where do you check battery temperature on M3 RWD?

So... OK , to summarize, car wastes energy to keep battery warm in an artificial ways (using heat pump or from the motors etc). Battery discharging process itself does NOT produce (enough or at all) waste heat, correct?

And.. heat pump uses liquid lines to control battery temperature.

The reason I asked that was to know how reliable that system is. Should we worry that 10 years from now these liquid systems might develop a leak, just like any antifreeze system on ICE cars, etc?

 

[Supcom]

Where do you check battery temperature on M3 RWD?

So... OK , to summarize, car wastes energy to keep battery warm in an artificial ways (using heat pump or from the motors etc). Battery discharging process itself does NOT produce (enough or at all) waste heat, correct?

And.. heat pump uses liquid lines to control battery temperature.

The reason I asked that was to know how reliable that system is. Should we worry that 10 years from now these liquid systems might develop a leak, just like any antifreeze system on ICE cars, etc?

Don't worry about it. Ten years from now Tesla will check the cooling system when they install the new battery.

 

[drtimhill]

I am simply curious, how does pre-conditioning work? Very specific questions here, thanks.

1. does it use liquid lines and some heat pump warms up the liquid which is transferred via some lines tucked in closely to the battery packs? Is it some dense and large liquid circuit OR does it use Air to warm up the battery like a space heater?

2. (unrelated to 1) does the battery warm ITSELF up during driving (similarly to ICE)? I mean: is there some chemical reaction that , when being discharged, keeps the battery warm? Or does the car have to waste energy during the whole trip to use another mechanism/circuit (as per 1 above) to keep battery warm?

Yes, the car can move heat between the various components to adjust temperature as needed (using a liquid coolant). This includes cooling the motors when needed and heating or cooling the battery. Since the battery has non-zero internal resistance there IS some heat generation when it is being charged or discharged, so yes, it does warm itself up to an extent. However, the car also actively warms the battery when needed, such as before supercharging. On the model 3/Y the car does this by running the electric motors slightly off-phase, which generates extra heat, which it then pumps to the battery. If you listen carefully you can hear a slightly different motor sound when it is doing this (its slightly higher pitched).

 

[Lon12]

I just watched my car pre-condition the battery this morning in my garage. Garage was -7ºC. Battery was +1ºC. Wall 240v charger is limited to 24 amps. It used both stators to heat the battery up to 11ºC before it would start charging. It took 30 minutes before charging started. The orange lines in the Tesla app were displayed until the battery started charging at 11ºC.

 

[AAKEE]

2. (unrelated to 1) does the battery warm ITSELF up during driving (similarly to ICE)? I mean: is there some chemical reaction that , when being discharged, keeps the battery warm? Or does the car have to waste energy during the whole trip to use another mechanism/circuit (as per 1 above) to keep battery warm?

I did some logging and took some photos during a 240km drive in -20C (-4F) drive today.
Text and pictures here:
Batt temps during drive