2020 Model 3 LR never stops charging [resolved]

[Frank99]

There is an efficiency difference, but it’s not huge-about 12% in my testing:

https://forums.tesla.com/discussion/comment/1883492/

If you drive 10,000 miles per year and pay $0.20 / kWh for electricity, you’ll pay about $500 a year for charging. Saving 12% means about $60 a year, so payback time on a $500 install of a 240v outlet is 8-10 years.

 

[Scelto]

Thanks for your thoughts @drtimhill - $500 for the L2 charger and $1300 for the installation is a lot of power for me to consume before it makes economic sense though.

The only thing that will drive me to that is if for some reason the passive ("vampire") drain becomes so high during the bitter Chicago winter that I see a large reduction in the 5mi/hr that I get from the 120v charger.

I usually charge to 80% at home.

The worst efficiency I've seen so far is 62% on the slow charge from 93%-100% reported above, with the 67 charges at home so far showing 80-100% efficiency, with an average of 87%.

I'll keep an eye on it though. Without stressing about it

 

[Frank99]

If you Model 3 is exposed to a Chicago winter, you will probably get zero (or possibly negative) charging using a 120V outlet. Pretty much all the power that you can pull from a 120V outlet will go to keeping the battery from freezing. Are you parking in a garage, or outdoors?

I'm not an expert on that area of the country, but I've read enough stories from people who live in semi-Arctic zones to advise some caution. Maybe someone with experience will pop in.

 

[Scelto]

If you Model 3 is exposed to a Chicago winter, you will probably get zero (or possibly negative) charging using a 120V outlet. Pretty much all the power that you can pull from a 120V outlet will go to keeping the battery from freezing. Are you parking in a garage, or outdoors?

It's in an attached garage.

The garage is unheated and at best poorly insulated.

I've never measured the temperature, but when it's -30 outside the beer and soft drinks we store out there as a makeshift fridge during the winter months stay nice and cold but never freeze. Not very scientific though, I know

I'm a data guy so maybe I'll stick a remote sensor out there this year to see if I can quantify the impact of lower actual temperatures on charging efficiency. Though as you suggest, I bet somebody's already done that!

Improving the garage, including insulating it, has been on my list of home improvements since I moved here in 2012(!), so I guess plan A will be to just stick a wall charger up if we really take such a big hit, but luckily we're not going to find ourselves stuck. Between routine low use and a supercharger in a nice indoor location ~9 miles away I'll still play the "wait and see" game.

 

[drtimhill]

Thanks for your thoughts @drtimhill - $500 for the L2 charger and $1300 for the installation is a lot of power for me to consume before it makes economic sense though.

yes the installation can mess you about. Fortunately in my case my breaker panel was right next to where I wanted the charger, so install costs were only $450.

 

[Pumpingiron]

I'm extremely fortunate. First I live in Cary, NC. We pay about 8 cents per KWH and lowest temp experienced in the last 30 years was about -10F for a few days. Next my 2 car garage has room for a small workshop so insulated windows, walls, ceiling and insulated garage doors were originally installed. The shop has a 240V 50amp breaker for my welder which I seldom use so it is now my Model 3 charger. I really feel for you guys in the far north...wish I could help.

 

[chamshaw]

Top up our M3 daily after various length daily trips. Keep it mostly between 50% and 80% but came to do this after a shorter day's run and, even with a gap between green block and limit line, message was 'charging complete'. Moved the line and put a bit more in, wondering.
From some of the above presume that the system equalised cell voltages while at leisure. I'm not bothered but what else could it have been?

 

[Frank99]

It happens. Some people report that the battery sometimes ends up one or two percent above where they set the charge limit, some report one or two percent below. Best guess is that the Battery temperature changes after charging completes (either cooling down or warming up), which changes the voltage that the car measures and uses to estimate battery capacity.