Preheating for no reason

[zecar]

Any good reason my car would be preheating the battery 4 hours before departure?

 

[OxBrew]

What's the outside temperature?

 

[DownshiftDre]

Also, interested to hear more about this particular cars environment. It could be a slow heating process for more uniform battery temperature.

I would love for somebody to deep dive further into the target battery heating curves with some scan tools for the various use cases where battery heating is used.

 

[Silicon Desert]

Chicago in the winter.... burrrrrr ! I wouldn't be surprised based on the temperature around the car. More facts please.

 

[Supcom]

It takes a long time to properly warm up a ton of battery.

 

[jsmay311]

Tesla’s Scheduled Departure behavior is egregiously/indefensibly wasteful when it comes to how much energy it wastes in cold temps to preheat the battery. As such, I would strongly discourage anyone who parks in cold temps from using it.

See here where I did a test and found it burned through 10% of my Model 3’s battery in a single precondition: Preconditioning Car Yield Full Regen Capability?

In that case, it started preheating the battery 2 hrs and 10 mins before the scheduled departure. I’m surprised it would start as early as 4 hours, but I probably shouldn’t be.

 

[OxBrew]

Tesla’s Scheduled Departure behavior is egregiously/indefensibly wasteful when it comes to how much energy it wastes in cold temps to preheat the battery. As such, I would strongly discourage anyone who parks in cold temps from using it.

See here where I did a test and found it burned through 10% of my Model 3’s battery in a single precondition: Preconditioning Car Yield Full Regen Capability?

In that case, it started preheating the battery 2 hrs and 10 mins before the scheduled departure. I’m surprised it would start as early as 4 hours, but I probably shouldn’t be.

I don't mind wasting all the energy it needs to waste, as long as it's plugged in.

When not plugged in, I'll also take whatever SOC hit necessary to keep the battery healthy when I drive the car. You can kill cells really quickly if you try to discharge them when they're too cold.

Tesla is better than everyone else at these kinds of algorithms, no one else is close.

 

[OxBrew]

Last night in Chicago it was reportedly 20° F, currently 27 ish. I agree, 4 hours seems early to start preheating the battery, but we don't know how long since the car was last driven (makes a huge difference), if it was plugged in all the time (so it can maintain a minimum battery temp), or if Tesla has figured out it's better to heat up a cold battery really slowly, using the same energy over a longer period for more uniform heat within the cells. The worst thing you can do is load a cell when it has a large temperature gradient across it, cold inside and hot outside. It will immediately start permanently delaminating layers, eventually killing the cell.

There's a reason Tesla says keep your car plugged in all the time if possible, especially in cold weather.

 

[Occhis]

Question for anyone who may know. Does leaving plugged in keep the battery at a certain specified temperature if scheduled departure/precondition is NOT set?

 

[OxBrew]

Question for anyone who may know. Does leaving plugged in keep the battery at a certain specified temperature if scheduled departure/precondition is NOT set?

I think the answer might be more nuanced than the question. IDK the direct answer, but I've read in Tesla patents that they can use the battery as a thermal battery also, a place to store heat from the cabin, using the heat pump to to move heat around.

I imagine that they really don't want to waste energy keeping the battery warm above the -25°F temp they warn about in the manual (don't leave it unplugged below -25°F for more than 36 hours? or something, I forget) but I would hope they try to hang onto the heat they have as long as possible, moving it around and keeping the pack at an even temperature.

 

[Ther0ck]

Any good reason my car would be preheating the battery 4 hours before departure?
View attachment 900330

Must be cold where you live. But yes I see this when it's -10c and colder. Typical where we live.

 

[OxBrew]

Question for anyone who may know. Does leaving plugged in keep the battery at a certain specified temperature if scheduled departure/precondition is NOT set?

Well it's 12°F this morning and the car started heating itself randomly for no reason. No one turned it on, no schedule departure or anything for over 6 months.

Parked it outside yesterday afternoon, plugged in, was 25°F or so, and pretty windy. Charged itself, done late evening. Temps dropped to 7°F overnight.

So it seems it will just heat the battery to keep it at some minimum temps. Inside the cabin shows 22°F (outside is still 12). So some residual heat radiating up from the floor must be keeping the interior warm.

 

[Occhis]

Well it's 12°F this morning and the car started heating itself randomly for no reason. No one turned it on, no schedule departure or anything for over 6 months.

Parked it outside yesterday afternoon, plugged in, was 25°F or so, and pretty windy. Charged itself, done late evening. Temps dropped to 7°F overnight.

So it seems it will just heat the battery to keep it at some minimum temps. Inside the cabin shows 22°F (outside is still 12). So some residual heat radiating up from the floor must be keeping the interior warm.

Interesting observation. Thanks for the response.