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Cold weather charging: charge at arrival or before departing?

AMGF

2018 Model3 AWD+; 2021 ModelS Plaid
Jun 30, 2021
431
1,834
Canada
I’ve had my Model3 for three years and have now added a MS Plaid but still I’m a bit confused as to what is the best charging time for the best battery life.

In the winter, with my Model3, I would always charge the battery as soon as I arrived home in the evening because I figured that the battery was warm and it would be healthier to charge it while warm.

Now I’m wondering if using the schedule charging to charge closer to my departure time if it would be better or worst for the battery? Doing that means that the car will start charging in the middle of the night on a cold battery. However I would leave in the morning on a freshly charged and warm battery instead of leaving on a cold one.

Anyone knows what is best? I tried searching for this but all I can find is that a plugged Tesla is a happy Tesla with no info on what is the best time to charge in sub zero temps.

Thanks!
 

AMGF

2018 Model3 AWD+; 2021 ModelS Plaid
Jun 30, 2021
431
1,834
Canada
In cold weather the battery management system will warm the battery first before charging. So, nothing to worry about. I have been doing the "before departure" charging for 7 years and no detriment to my knowledge. After over 300k kilometers I have lost 9% of capacity. No degradation in the last year.
Good info thanks. I lost 6 or 7 % on my 3 in 3 years. A bit more than I expected.
 

GtiMart

Active Member
Nov 13, 2019
1,830
1,700
Quebec City, Canada
Yep, the car will manage. IT will not charge a battery that's too cold, it will heat it up. Charging for departure means you will leave home with a warm battery. That has the advantage of being a bit more efficient, and you will have access to full regen. Charging in the evening means the battery has time to cool at night and you might drive without regen for a while in the morning. That is, if you live in an area that can see freezing temps.
 
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ecarfan

Well-Known Member
Moderator
Sep 21, 2013
19,507
14,535
West Vancouver, British Columbia
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B_E_V

Member
Apr 18, 2021
42
35
New Hampshire
Keeping the car plugged into power means the car does not have to draw down the battery to satisfy standby demands like sentry mode, keeping an internet connection live, etc. To some extent you can think of your battery has having a limited number of charge/discharge cycles. So limiting those cycles as much as possible will extend how many years the battery lasts. A plugged in car is a happy car.

I think it also depends on how low you are discharging, and how high you are charging. I have read that the sweetest range is to keep an NCA battery between 30% and 70% state of charge, with 20 to 80% almost as good. So if you have discharged it below 30% then I would definitely charge immediately. If you are planning to charge it above 70 or 80%, then I might postpone charging. If your are going to charge past 90% then I would definitely wait to charge at the last minute. (This paragraph does not apply to LFP batteries.)

You might save a small amount of energy by charging while the battery is already warm, instead of making the charging system warm the battery before a later charge. On the other hand, if you are going to precondition while plugged in before leaving at a predictable time, both for comfort, and to minimize charge/discharge cycles, the battery will be warm either way.
 
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AMGF

2018 Model3 AWD+; 2021 ModelS Plaid
Jun 30, 2021
431
1,834
Canada
Keeping the car plugged into power means the car does not have to draw down the battery to satisfy standby demands like sentry mode, keeping an internet connection live, etc. To some extent you can think of your battery has having a limited number of charge/discharge cycles. So limiting those cycles as much as possible will extend how many years the battery lasts. A plugged in car is a happy car.
That was the point I am concerned about. In cold temp, if you charge on arrival the battery is warm. But the charge will be completed after a few hours so the battery will freeze and lose % and then the car will charge every now and then during the night as % drops.

By charging before departing, the battery still freezes, but you only charge it once and not every now and then as the battery freezes.

I think I have my strategy. Charge on arrival if the battery is low, warm battery will make charging easier. If the charge is not too low, I’ll simply charge prior to departure (but still plugged in so Tesla battery management can do its things if it needs). That way the car battery won’t charge as the % drops due to low temp limiting charge cycles. I’ll always have a warm battery so I can use regen and will likely help the range on cold days.

I’ll see how this goes.
 
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That was the point I am concerned about. In cold temp, if you charge on arrival the battery is warm. But the charge will be completed after a few hours so the battery will freeze and lose % and then the car will charge every now and then during the night as % drops.
I think your strategy is reasonable.

However, I think that you are treating those "charge every now and then during the night" events as each nearly equivalent to the full initial charge after arriving home. Instead I think you should think in terms of "Full Cycle Equivalents," which are different from simply counting amp hours of charge.

I found this article quite informative: The Comprehensive Guide to Maximizing your Tesla’s Battery Efficiency and Battery Life.
 
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