Model 3 Drain - Tesla Service Response

[Adopado]

Hi,

I am having problems with my car losing between 2-5% of the charge in the first few hours after being charged. Came with it to tesla service, see below answer. Would you accept it?
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I see this level of variation at the moment. It seems to depend on temperature variations between night time and daytime and perhaps between software versions. Because this is purely an initial change rather than sustained "drain" (i.e. if the car is left for a longer period undisturbed it hardly loses any more) I put it down to the challenge of the BMS being able to accurately represent the percentage capacity because, as we know, this figure varies by temperature*. You are misrepresenting the situation in saying to Tesla that 6% a day is a problem ... you appear to have simply doubled the initial 3% "loss" when in fact the car does not continue losing capacity at the same rate.

* Let's say the night charging temperature is 0º C and charges to 80%. That is 80% of a slightly lower capacity (because the battery has a lower overall capacity at that temperature. When your battery warms to 8ºC next day the overall battery capacity is higher ... so the amount that is stored after last night's charging now only represents 78% of your useable capacity. Add in a normal 1% loss ... and there you go. I can't say that this is exactly what's happening in your case but it seems reasonable to consider these factors.

 

[init6]

See the bit on the states chart around 12:00 on the 2/18? I can't quite tell from the colours if the car was offline or charging. Might be worth doing the graphs again for that period.

 

[init6]

Also, the two blue lines after that period. Were you checking the app at that point? It's unusual to see two 'wakes' in the same period. Although as other have said it might be trying to download an update.

 

[Jason71]

I see this level of variation at the moment. It seems to depend on temperature variations between night time and daytime and perhaps between software versions. Because this is purely an initial change rather than sustained "drain" (i.e. if the car is left for a longer period undisturbed it hardly loses any more) I put it down to the challenge of the BMS being able to accurately represent the percentage capacity because, as we know, this figure varies by temperature*. You are misrepresenting the situation in saying to Tesla that 6% a day is a problem ... you appear to have simply doubled the initial 3% "loss" when in fact the car does not continue losing capacity at the same rate.

* Let's say the night charging temperature is 0º C and charges to 80%. That is 80% of a slightly lower capacity (because the battery has a lower overall capacity at that temperature. When your battery warms to 8ºC next day the overall battery capacity is higher ... so the amount that is stored after last night's charging now only represents 78% of your useable capacity. Add in a normal 1% loss ... and there you go. I can't say that this is exactly what's happening in your case but it seems reasonable to consider these factors.

this is kind of what I was thinking only opposite .Cold reduces the rate of chemical reactions so is likely to reduce the current voltage not the theoretical capacity.
When the car finishes charging the battery is warm due to the charging. then it cools over night and in the morning it appears to have lost some charge. In reality it is just the cold battery and the sluggish electrons. I find that if I don't drive the car then check it at midday if it has been sitting in the sun then all the "missing" charge has come back.
So I agree it is the difference between readings at different temperatures but I think it works the opposite way around to what you describe, at least in my experience. I think the cold supresses the current charge level not the maximum capacity.

Either way Op needs to check the charge once the car warms up. Or just don't worry about it. You will get the charge back when you start to drive you just wont see it since the % will drop as you drive which will mask it.

 

[init6]

Good points. Can you throw in a temperature graph as well please? We've no idea what the temp difference is overnight. You may be in the Blue Toon for all we know

 

[init6]

Sorry, just had another thought. Can you share the drives dashboard? (hide the addresses from the screen grab) Teslamate will have a little snowflake against the drive if there is significant variation in useable and actual battery levels.

 

[Adopado]

Sorry, just had another thought. Can you share the drives dashboard? (hide the addresses from the screen grab) Teslamate will have a little snowflake against the drive if there is significant variation in useable and actual battery levels.

... talking of snowflake symbols ... despite cold nights I have seen fewer snowflake symbols on the car screen or in the app this winter. I only thought about it yesterday when we had the car displaying the snowflake symbol for the first time for ages.

 

[piotroek]

this is kind of what I was thinking only opposite .Cold reduces the rate of chemical reactions so is likely to reduce the current voltage not the theoretical capacity.
When the car finishes charging the battery is warm due to the charging. then it cools over night and in the morning it appears to have lost some charge. In reality it is just the cold battery and the sluggish electrons. I find that if I don't drive the car then check it at midday if it has been sitting in the sun then all the "missing" charge has come back.

I'll give it a test, trick is - to charge to 60, check in the morning charge level, and then leave it till later afternoon when car is warm. BTW the same happened when temperature outside was 15+

 

[piotroek]

Sorry, just had another thought. Can you share the drives dashboard? (hide the addresses from the screen grab) Teslamate will have a little snowflake against the drive if there is significant variation in useable and actual battery levels.

Drain is a bit random, I'll add drives later. and try combining come details onto single chart.

 

[init6]

Snowflakes galore. i bet your drives has something similar.

 

[Jason71]

I'll give it a test, trick is - to charge to 60, check in the morning charge level, and then leave it till later afternoon when car is warm. BTW the same happened when temperature outside was 15+

The other question is does it continue to happen. if it is only straight after a charge or a drive then I am fairly confident it is temperature related but if it is loosing more than the equivalent of 1% a day max when not driven then you may have an issue.
You have been a member a while so I am going to assume you know about phantom drain and the effect of Sentry mode etc but is this a car you have had a while and this has suddenly started or is it a new car?

 

[init6]

just spotted the SOC rising at the end of this chart even though there appears to be no charging taking place. Another area to zoom in on

 

[GlynG]

this is kind of what I was thinking only opposite .Cold reduces the rate of chemical reactions so is likely to reduce the current voltage not the theoretical capacity.
When the car finishes charging the battery is warm due to the charging. then it cools over night and in the morning it appears to have lost some charge. In reality it is just the cold battery and the sluggish electrons. I find that if I don't drive the car then check it at midday if it has been sitting in the sun then all the "missing" charge has come back.
So I agree it is the difference between readings at different temperatures but I think it works the opposite way around to what you describe, at least in my experience. I think the cold supresses the current charge level not the maximum capacity.

Either way Op needs to check the charge once the car warms up. Or just don't worry about it. You will get the charge back when you start to drive you just wont see it since the % will drop as you drive which will mask it.

You could have a point here, my car sits in a heated garage, no windows and insulated roller shutter door, the floor is also carpeted therefore the temperature within is fairly constant and that may explain why my car suffers very little indicated loss.

 

[Jason71]

You could have a point here, my car sits in a heated garage, no windows and insulated roller shutter door, the floor is also carpeted therefore the temperature within is fairly constant and that may explain why my car suffers very little indicated loss.

Do you read it a bedtime story as well?

 

[init6]

Do you read it a bedtime story as well?

Maybe that why so many cars don't sleep well?

 

[piotroek]

The other question is does it continue to happen. if it is only straight after a charge or a drive then I am fairly confident it is temperature related but if it is loosing more than the equivalent of 1% a day max when not driven then you may have an issue.
You have been a member a while so I am going to assume you know about phantom drain and the effect of Sentry mode etc but is this a car you have had a while and this has suddenly started or is it a new car?

that is not the case, I am losing charge only straight after charging. When not charging - I can leave it for a week and see only 1%ish lost over 168 hours.
My problem is that it has started to happen in September. Funny enough I charged the car overnight last night to get nice fresh data set and today nothing was lost...

 

[MrBadger]

I really do not think that you are seeing anything unusual. Everything that has been shown has a plausible explanation for 'normal' (at least for many other cars) battery SoC % behaviour. I think Tesla's response is a perfectly valid explanation. Ultimately, its how the battery behaviour averages out over a period of time and if you are witnessing 1% over 168 hours then I think that, and your graphs are showing both + and - SoC changes, its a pretty good reason not to worry.

tl;dr - battery % does fluctuate up and down for any number of reasons.

 

[JRoque]

Hello OP, I have this issue as well. I've had it for years on my 2018 MR.

In my case, it will drain my battery in about 5 days if left alone during this condition. It happens most often when the firmware has recently updated. I sort of stop the battery drain by rebooting the car. Give this a try next time you notice it.

It has happened after charging, now that you mention it. In fact, it happened just last week where I charged the car to 80% and it drained down to ~3% in 4 or 5 days. I did not use the car once during this time. I charged it again and noticed it was still doing it. I rebooted it and the drain seems to have stopped - until next time.