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Leaving Tesla plugging in during cold weather

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I was reading cold weather tips here:

Winter Driving Tips

It says:

Leave Your Tesla Plugged In
We always recommend leaving your Tesla plugged in when it’s not in use. This is especially helpful when it’s cold as staying connected helps your battery retain the heat it needs to operate efficiently and leverage regenerative braking.

What are they trying to say? Are they saying that plugged in car will keep the battery warm on its own without preconditioning?

I was close to getting a charger where charing only works on 11 pm and 7 am. I will certainly leave the car plugged in at all times but with this option there is no option to charge during day time. Charger simply shuts down during day time so there is no power available. We are in MN where it is bitterly cold. We have insulated garage but it still get super cold during winters.

For me I can save $500 on rebate and another $500 for install costs if I select a charger where charging is only allowed during off peak hours.

If I will get better range during cold weather by keeping car plugged in during winters I would be willing to select "Time of use" charging where I can charge at any time but pay a bit more during day time along with additional $1000 for install.
 
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Regardless of the why. Its a good idea to leave it plugged in. In winter, you might want to start charging so that the charging cycle ends close to your home departure time. That way the battery is already warm/hot vice starting at 6 pm and finishing at 10 pm.

Remember: A Happy Tesla is a Plugged in Tesla.
 
Regardless of whether the Tesla will maintain the temperature of the battery pack while parked (whether plugged in or not), during the work week, if you are not home during the day it makes no difference. In the evening when you arrive back at home the battery pack will be warm from driving, remain warm for many hours. If you start charging as early as 11PM the pack will still be warm; if you delay charging so that charging finishes by 7AM the car may need to warm the battery pack a bit as required for charging, then the battery pack will be warm when you leave in the morning. Either way you will want to precondition the Tesla for your comfort before you leave. If your time of use plan will not charge after 7AM then the power required for preconditioning will be taken from the battery instead of using the charging station as a source of power to warm up the passenger cabin.

To determine whether the Tesla will warm the battery pack when parked, plugged in and not charging you would have to be able to track the power consumption outside of any delayed charging window that you set. If you have a smart charging station you might be able to obtain a log of the power usage over the preceding 24 hours. Power use during the specified charging window would be easy to spot as it would be somewhere between 8kW up to 11.5kW depending on your charging setup. Lower power use outside of the charging window could be due to cell balancing but if you observe a brief cyclical power drain of a few kW every few hours that lasts for perhaps 15 minutes this is most likely the battery being warmed.

Another way to determine if the battery pack is warmed when the vehicle is plugged in would be to charge to your normal charging setting, i.e. 80% and then change the charging limit to a lower value, i.e. 60%. Now unplug the charging cable and reconnect the charging cable. The vehicle should not begin charging because the battery is already above the charging limit. Leave the vehicle plugged in, in cold weather, for as long as practical (more than 10 or 12 hours.) Do not precondition the vehicle before driving; if you observe the blue snow flake symbol next to the battery icon on the driving screen this indicates that the battery is cold; this will limit charging and regenerative braking until the battery pack has been warmed. If you do not see the blue snow flake symbol then the battery temperature was maintained and charging and regenerative braking should be available. Repeat this experiment without plugging in the vehicle, leave the vehicle for at least 10 or 12 hours. If the battery is cold then you will see the blue snowflake symbol and charging, regenerative braking will be limited or unavailable.

To ensure that the battery is warm so that regenerative braking is available use delayed charging, set charging to start as late as possible so that the battery is warm when you start driving.
 
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I would definitely take that cheaper limited time of use. It doesn't cause any harm to the battery to get cold. It can handle that easily. But the energy usage is just going to be really high when you first start driving, which is OK. The energy is going to be used sometime. If you were to preheat at your house, so it's warm when you leave, then you're using the energy before you drive. If you don't, then it's just going to use that energy while you're driving. It's going to be pretty similar either way. At least with letting it use the energy while you drive, it's only using as much energy as it needs to, rather than maybe using up a lot more than necessary if you're trying to preheat at home.
 
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