Longer to charge at home in colder weather?

[DrGriz]

I'm the OP...

FWIW I don't see the heating symbol in my app. Is it for the US models or International models?
Regarding 29A/48A - I thought I saw something about a loose connection or wiring issues causing that. It was my understanding that the app should report the full current used to charge the battery and/or condition the battery.

The 29 amps was early in the session and ultimately, you can see from the snip from Teslafi, the average amperage for the session was 42. The average amperage from the long session the night before was 24. Maybe that could be a loose wire.

I welcome comments.

 

[AAKEE]

I dont believe all battery heating is represented by the heating symbol (I believe some people refer to it as "bacon"), but I am not someplace where its cold enough to ever see the bacon icons.

Just like we dont see the snowflake icon when the battery is "cool enough to limit regen but not cold enough to remove some capacity", I dont think we see the bacon icon for all battery heating either. If I am wrong about this, someone will correct me.

I do not check the app at all times, so I dont know about the bacon icon. My guess is that at least any time we see it, it heats the battery. Maybe it doesnt show at all times like when part of the charging is used to heat or keep the temp of the battery.

Tesla has change the snowflake limit, and also the temperature that the battery preheats during a planned departure with conditioning. Last winter we saw about 6.5-6.75C when using planned departurte. The snowflake was not present during a trip where a planned departurte was used. This winter, so far, the snowflake could be seen until the battery reasched about 10C. A few bugs in 2022-36.X caused the snoflake to go away briefly at 6.5C but it came back and ws present until about 10C. I think the software programmers was severely drunk as the go awaty and come back for the snow flake was seen a couple of times and went away a couple of times. Because of this, it was har to se a fixed limit where the snowflake was really precent.

My guess is that Tesla did see a degradation a bit higher than they wanted so they adjusted the preheat for planned departure, the snowflake and the regen power at low batt temp /and higher SOC. They also adjusted (more than one year ago) the normal cell temp target for *any* drive, and if compared to early 2021 they overall increased the cell temp target. I also belive I se a much higher cell temp at low SOC on my 2170L battery, and this make the battery not as bad when it comes to engine power.

 

[DrGriz]

Here's some data that might be useful for the OP's question.

Two recent charging sessions. Cold ambient temps, but actually quite similar according to the record, around 24 degrees, so that should be a wash.

First session, car had just completed a ~20 mile drive, and we plugged in immediately on arrival home.

The second session, this morning, I had let the car sit overnight so the battery was cold (Ambient temp was 22 degrees F, so a little colder than the previous charge).

Average amperage and efficiency were reduced. There was battery heating for the second but not the first charge session.

For the cold battery, it took roughly 5.8 minutes per percent charge. For the warm battery it was 4.3 minutes per percent. So a 35% bite in terms of time to charge.

Obviously from the chart the efficiency in terms of kWh was down by 18%

I realize we know that battery heating is the issue, but these are some actual data points that might help put some numbers to that.

 

[derotam]

So yesterday I took some data about battery heating while on AC charging(24A/240V). Nothing too interesting but it is a graph to let people kind of see what is going on with a temperatures(and other data) vs time plot. Time is in seconds so this is over about 17 minutes of data from my OBDII adapter and SMT.

Text summary of data:
This is on a 2018 LR RWD
~17 minutes of elapsed time
Start/End Battery Temp - 2.75/6.75 celcius
3-3.5kW pushed to rear motor to generate heat for the battery, balance going to charging.
Stator Start/End temp - 1/41 celcius

Graph:

 

[STS-134]

@AAKEE Well I think this:

So yesterday I took some data about battery heating while on AC charging(24A/240V). Nothing too interesting but it is a graph to let people kind of see what is going on with a temperatures(and other data) vs time plot. Time is in seconds so this is over about 17 minutes of data from my OBDII adapter and SMT.

Text summary of data:
This is on a 2018 LR RWD
~17 minutes of elapsed time
Start/End Battery Temp - 2.75/6.75 celcius
3-3.5kW pushed to rear motor to generate heat for the battery, balance going to charging.
Stator Start/End temp - 1/41 celcius

Graph:

answers this:

Now the question is, if you connected to a EVSE that could do 12kW, would it use 3-6kW to preheat and put anything into the battery right after you plugged in? Is the reason it's not putting any energy into the battery simply because it decides it's better to use it all for preheating and it doesn't have anything to spare?

At least in the scenario where the battery is only about 5°C too cold. Although I'm curious about whether the car would ever pump a full 6 kW or more into the battery using either the motor stators or heat pump if it needed to heat the battery by 20°C for charging. I'm guessing that the reason it seems reluctant to use the heat pump is that it may be located in a confined space when it's parked.

 

[GtiMart]

There is no heat pump on a 2018. Heating the battery must be done through the stators.

 

[STS-134]

There is no heat pump on a 2018. Heating the battery must be done through the stators.

Whoops, missed the part about it being a 2018. Indeed. I believe heat pumps started going in during 2020.

 

[zannman]

This is one of my favorite days of TeslaFi data because it shows how much temperature affects 120v charging.

We were in process of moving to a new house a few hours away from our old one. Arrived just before 8am at 14 degrees F with a warm battery and plugged into 120v. Charged incredibly slow - adding only 1.47kWh of charge over 4 1/2 hours while spending a lot of energy to maintain battery temperature. By around noon the outdoor temperature had increased to 25 degrees F and a little over 30 in the metal building garage where the car was moved to.

The 12:30pm -2pm charge was my first at that location after installing 6-50 240V charging outlet and shows the huge difference in charging speed at these temperatures.

In short it was beneficial if not absolutely necessary for us to prioritize the electrical upgrade over a lot of other moving related activities because of the weather.

 

[AAKEE]

Whoops, missed the part about it being a 2018. Indeed. I believe heat pumps started going in during 2020.

Heat pump from facelift very late 2020.

 

[AAKEE]

@AAKEE Well I think this:

answers this:

At least in the scenario where the battery is only about 5°C too cold. Although I'm curious about whether the car would ever pump a full 6 kW or more into the battery using either the motor stators or heat pump if it needed to heat the battery by 20°C for charging. I'm guessing that the reason it seems reluctant to use the heat pump is that it may be located in a confined space when it's parked.

The battery will have a different temperature target depending on the charging power.
And charging below 0C (freezing point) will modt probably not be done.

When I charge outside with the UMC + schuko connector at max 3kW, it initially do not charge the battery at all. All 3kw is used to heat the battery until (not 100% sure) 5-6C. After long time the stabilized values is 8,75C batt temp with around 1kW heating and 2kW charging.

When I charge with the WC (11kW, 3 phases 16A 230V) inside the garage I think batt heat is not on and the resulting about 22-25C batt temp is heat genereted from the charging.

 

[DuncanM]

M3 L1 charging at 12amps: 8 hours in a warm garage vs 8hours outdoors at 27F to 22F:

Summary: No difference.

This mirrors my experience in similar temperatures.

 

[STS-134]

M3 L1 charging at 12amps: 8 hours in a warm garage vs 8hours outdoors at 27F to 22F:

Summary: No difference.

This mirrors my experience in similar temperatures.

The battery is fairly well insulated. I wouldn't expect the car's location (inside or outside) to have much of an impact after the battery reaches the proper temperature. The HVAC system wouldn't use the battery as a heat storage device and dump extra cabin heat into it after you park on a cold day if it wasn't at least somewhat well insulated.

 

[DuncanM]

The battery is fairly well insulated. I wouldn't expect the car's location (inside or outside) to have much of an impact after the battery reaches the proper temperature. The HVAC system wouldn't use the battery as a heat storage device and dump extra cabin heat into it after you park on a cold day if it wasn't at least somewhat well insulated.

Yes, I agree. Although wind and substantially lower temps would probably make a difference.

The outdoors test was done the next day after the owner returned from work and he let it cool until midnight before charging.

 

[AAKEE]

I didnt care to look at the video. Did they let the car stand outside to let the battery cool down ?

27-22F is below freezing ( 0C) so if the car had been cooled down there had been a need for battery heating as Tesla do not allow charging below 0C. Lithium batteries doesnt like to be charged at or below freezing. Batteriy below 1C would need heating.

For me charging with a 1phase 230V (3kW) the car every now and then needs to heat the battery even if I start the charging when arriving with rest heat in the battery. Parked after a long drive around time 20:00 (8pm) with battery temp 16.75C. Connected the car asap to get the benifit from the battery temp from the drive. After about 6hrs the battery was down to 7.5C and that did trigger the battery heating. The heater in on at about 7.5 to 8.25C and push the temp up. Outside temp was -9.5C to -6C ( 15 to 6F)

At 1C, the max BMS charge limit enters 0kW as can be seen at the note in this picture.
The car was charged 03:30 to 06:20 and the cell temp did rise from 4C to 19.25C without any battery heating at all.

If the car has been outside, and the battery has cooled down to low temperature the battery heating will go on and depending on how much charging power that is used, the efficiency will go down and the time to charge will go up.

This is teslafi numbers, and the efficiency often is 85-95% on UMC signle phase 3kW charging at my mother in laws place.
This charge was timed to not have to cool battery. Efficiency 62%.

The worst charges did end up at about 35-37% efficiency, if the battery already did cool down, and then comnected to that single phase 3kW charges. Then it forst would not charge until the battery was a few degrees C. Before this only battery heating and during the charging battery heating would be needed to keep the temp up.

 

[DuncanM]

I didnt care to look at the video. Did they let the car stand outside to let the battery cool down ?

Yes, the owner let the car cool before charging and the cold battery (snowflake) warning was on. There's a number of similar videos on YT, some in much more extreme low temperatures. I think the key factor is having the car protected from wind (or charging in low wind conditions), so that the battery can better retain the heat generated by the battery heater.

 

[AAKEE]

Yes, the owner let the car cool before charging and the cold battery (snowflake) warning was on. There's a number of similar videos on YT, some in much more extreme low temperatures. I think the key factor is having the car protected from wind (or charging in low wind conditions), so that the battery can better retain the heat generated by the battery heater.

The snowflake was on until about 6.5-7C celltemp the last year. (Different software could change this).

I did see the snowflake up to 10C a few weeks ago, on 20220.36X. Havent really checked this winter but the snowflake is present at higher celltemps so the car maybe hadnt cooled the battery completely.

 

[toolman335]

People with 5-15 120v outlets in cold climates can easily end up in a situation where there is not enough power being delivered to warm the battery, so the car actually never charges, despite being plugged into an outlet overnight (or longer).

I live in a cold climate and I'd never use 120 power in the winter. I wouldn't own the car if I that was my only option.

 

[lowercase]

It's -20 outside but about zero-ish in my garage, and I find if I charge at home at 12A/110V (about +8km/h) it SAYS it will take 12 hours to charge, but it continues to charge at the normal rate -- about +2% per hour -- at roughly 85% efficiency.

2022 RWD with LFP battery.