Best practice for keeping battery warm

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FF35

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#1
LR RWD, I use 50-60% of my battery a day and keep it between 20-80%.
Scenario is a temp of 10 degrees F.

Maybe someone with CAN data can do this test or someone knows. Trying to figure out what keeps the battery warmest for the most amount of regen when leaving in the morning.

Is it better to slow charge for 8-10 hours around 10-15A or charge at 48A a few hours before leaving?
 

JWardell

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#2
Either way will keep the battery slightly warm so you will have partial regen. I typically kick off charging 15-30 min before I leave on below freezing mornings to help things.
But it't only going to actively warm the battery enough to support the charge rate. At least you have a full 48A but I'm not sure that is quite enough to add additional internal heat like a supercharger would.
The best solution is to add a heated garage :)
 

Jay79

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#5
Scheduled charging will help and the closer you leave to 6am the better since that will be its warmest. I myself don't leave the house until 9am so I think using the timer to start charging will work better for me. This way my battery won't sit for 3 hrs getting cold. I wish they would make scheduled charging not shut itself off after 6am, its kinda self defeating in my eyes.
 
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michi84

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#7
No experience with real freezing temperatures yet, but here is what i do to maximise available regen:

1) Set charge limit to 80% instead of 90%: the amount of allowed regen power is not only dependant on battery temperature, but also SOC. At 90%, you need about 30°C cell temp to get full regen, at 80%, 20°C are enough.

2) Use scheduled charging to finish charging as closely as possible to planned departure time: this is now easier with the 15 min increments. I have found an easy way to calculate charging time: (charge limit - current SOC)x4,4 - this empirical formula gives a close approximation of charging time for an 11 kw AC charge (48 amps or 3X16 amps like here in Austria). This allows for some minutes of battery heating, in freezing temperatures you might need to add some 10-15 minutes.

3) With ScanMyTesla, i can also see how many kWh will be needed to complete the charge, and divide that by the average sustained charging rate which is about 10,2 kW. Then allow for some extra time for battery heating.

I cannot use scheduled departure, since i rarely leave home before 9 am, and departure times vary wildly. Experience shows that a long enough charge (more than 90 min) will give me cell temps around 18-20°C at 5°C ambient temp. Longer charges 1-2°C more. Will be interesting to see how this develops in freezing weather. Charging rate is reduced to 4 kW below 10°C cell temp. Experience will show how long heating takes. If you are too conservative, and charging would be finished too early, you can always bump up the charge limit a few percent while you are getting ready to leave (another reason for 80% as target).

I use the same strategy in warm weather, since it is good practice to minimise sitting at high SOC longer than necessary. The multiplicator might be dependent on your battery health and other factors, to be sure, you can time a couple of charges. I used my teslafi data to come up with it some time ago.
 
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#8
How do you know your battery temp?
How do you preheat your battery?
How to do you schedule a charge -- don't see it on my app?
 

Dick Blonov

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#9
How do you know your battery temp?
How do you preheat your battery?
How to do you schedule a charge -- don't see it on my app?
- No battery temp gauge on the Model 3 apart from the blue indicator/snowflake
- Start charging/pre-heat the cabin
- You schedule from the car's charging screen, not the app.

Here's a Thread on the subject.

Phil
 
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