Schedule charging to maximize battery heat in freezing weather

[BerTX]

Yes, good point and a couple of folks mentioned similar things. I still think it would be a decent approximation since when I have manually charged on my destination charger over the summer nights as compared to really cold 20 degree winter nights of last winter, I saw very little difference in the amount of time it took to charge from various levels during the night. In fact within 15 minutes (less than 1 percent charge) of what I expected.

So sure, even with variables that can occur during the night, it would still be good enough. Now having said that, I can just see the complaints coming in that the estimation was off by 30 seconds and someone will be terribly upset

The other thing that the API does not have (and therefore no app can have) is the ability to set the charging amps. Even Dashboard for Tesla asks what charge rate you have set when you schedule charging, because it can't change it.

 

[derotam]

So if I’m adding let’s say 40% charge to my car it’s cheaper $ to charge the 40% to a warm battery then a cold one?

Basically yes. It doesn't matter how much you want to charge the battery though. No matter how much you want to charge the battery, if the battery is cold, you will be using more power to get to a certain charge level because some of the power will be going to heat the battery. If the battery is already warm, then you will only be putting in the power required to charge the battery, not heat and charge.

 

[Silicon Desert]

Basically yes. It doesn't matter how much you want to charge the battery though. No matter how much you want to charge the battery, if the battery is cold, you will be using more power to get to a certain charge level because some of the power will be going to heat the battery. If the battery is already warm, then you will only be putting in the power required to charge the battery, not heat and charge.

Good point. For me, I don't put much consideration into the "waste energy" of heating the battery while charging. From what I have seen on our MX when charging at night in very cold temperatures, the battery heater isn't on for more that just a few minutes during the whole night of charge. Usually, it is on at the beginning to sort of kick-start the charging, then the little heat that is generated from the charging process seems good enough to not require the heater any longer. Example, last winter when charging with the home Tesla wall connector on nights when the external car temperature was between 10-20 degrees F at least 6 hours after driving the car, the heater was typically on for less than 10 minutes during the night when charging. For this year, winter is just starting, yet in the last 2 weeks when charging in the early morning at under 20 degrees F, I have yet to see the heater even come on in the logs.

Yea when the heater is on, it is a significant 6KW, but fortunately for us, it is not of any big concern. I realize it can vary from model to model, temperature, electricity cost, time charging, and other factors, so your experience may not mirror mine. I suspect that below zero temperatures outside the car might yield greatly different results. It's just never gotten below 0 F up here yet. Coldest has been about 10 degrees F in the winter.

 

[f8K37Sq31]

I'm thinking ahead for the winter months of freezing temperatures. I know charging the battery generates heat. Logically, I'd like to schedule my car to charge so that it finishes when I'm ready to leave for work in the morning. I know I can set the time to START the charge in the car, but there is no easy way to enter the time to STOP charging and then have it calculate and set the start time accordingly.

If the app would allow you to set the start time, I could just plug in the charger, then use the app to delay it based on the estimated charging info. Not convenient, but it could suffice.

I have written two apps that may help you with this:

1. Smart Battery Prep: ‎Smart Battery Prep: For Tesla
2. Stats for Tesla (includes the above feature plus a lot of other features and stats): ‎Stats: For Tesla Model S/X/3

The app adds a top-off charge at the designated time so that your battery is conditioned by the time you intend to use the car.
Here is how it does it: https://www.maadotaa.com/batterycond

 

[mswlogo]

I'm thinking ahead for the winter months of freezing temperatures. I know charging the battery generates heat. Logically, I'd like to schedule my car to charge so that it finishes when I'm ready to leave for work in the morning. I know I can set the time to START the charge in the car, but there is no easy way to enter the time to STOP charging and then have it calculate and set the start time accordingly.

If the app would allow you to set the start time, I could just plug in the charger, then use the app to delay it based on the estimated charging info. Not convenient, but it could suffice.

Just checking if your interest is in minimizing the cost to run the car or you just simply can’t (or just don’t like) driving the car without out “full regen”.

Because if you want to maximize wasting energy and spending the most money to run it, this is great way to accomplish that !!

You are best off charging when the battery is already warm when you get home. It’s probably better for longevity of the battery as well. Heating and cooling something is part of what ages things. That will use the least total energy. If you have off peak metering then that is probably the cheapest time to charge.

The minor difference you will see in regen limit will be neglible on any energy saving. But waiting until your battery is cold to charge it will be a significant loss.

And to top that off you can actually get better wh/mi with LESS regen if you understand how things really work here and know how to apply it.

If this was such an obvious way to improve efficiency don’t you think Tesla would have done it. They don’t because they know it’s wasteful.

Best way to increase range is to preheat cabin for 5 minutes so you don’t use as much battery when you first get going to heat the cabin. Preheating battery gets you nothing.

Also charging at home rates heats the battery VERY little. It will heat it enough to accept charge (at home rates). But no where near enough to accept full regen charge (which is very high watts). So it will still be mostly limited if the battery was cold to begin with.