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Unexpected Battery Discharging - How worried should I be ?

2016 MS90D driver here with only 47k miles on the clock (the car, not me !).

I don’t watch my battery %age indicator obsessively … but I know that it discharges about 2% per day when the car is left sitting in the garage.

For the last week (3 power-cycles) I’ve noticed a “sudden” (i.e. within a couple of hours) drop of 5% in each cycle. I’m pretty sure that this is new behaviour.

Quick example :-
Mon evening: charged to 82%. Drove home in 3% (normal). Result 79%
Tue: awoke to 78% (lost one overnight – normal).
Did a midday trip of 4% each way (normal) –result 70%.
Stayed at 70% for several hours.
Tue evening – noted now 65% ! So 5% “suddenly” lost.
Wed: awoke to 64% (lost one overnight – normal).

I don’t think that this 5% loss is normal - and it’s hard to imagine that ~5kWh of energy has actually been “used” in a couple of hours. Any observations/suggestions ?

Am I worrying over nothing – or should I be making a Service appointment ? Is there even such a thing as a Mobile Service Battery Health Check ?

I can live with a 5% loss – as long as it is only once per cycle. However, if this is just the start of something more serious then I am worried – especially as my warrantee expires … Next Week !

Note - I’ve never charged to 100% before - would doing so perhaps “reset the BMS” ?
 
Could it be something like the car being awake to download a software update in the background? Did you use the app a lot, or change any software that might ping the car and wake it up? A new version of a widget or an app or something?

The non-linear nature of the draining does sound a bit odd, and wouldn't fit with the sort of usage I'm mooting, but I don't have any better ideas.

I can't say I've noticed anything similar in my MX90D, but then I really don't pay much attention. Sorry I can't be of more assistance.
 
I've noted this since the 36.5 update that introduced the new energy usage graphical display. Not sure if the update changed anything else related, but I've had drops of 3, 4 and 5% between parking up late morning and driving again next morning. And, 2 nights ago, a reported *increase* of 1%.

So, I'm somewhat unclear on what's happening, but it does seem to be behaving differently to previous versions.
 
2016 MS90D driver here with only 47k miles on the clock (the car, not me !).

I don’t watch my battery %age indicator obsessively … but I know that it discharges about 2% per day when the car is left sitting in the garage.

For the last week (3 power-cycles) I’ve noticed a “sudden” (i.e. within a couple of hours) drop of 5% in each cycle. I’m pretty sure that this is new behaviour.

Quick example :-
Mon evening: charged to 82%. Drove home in 3% (normal). Result 79%
Tue: awoke to 78% (lost one overnight – normal).
Did a midday trip of 4% each way (normal) –result 70%.
Stayed at 70% for several hours.
Tue evening – noted now 65% ! So 5% “suddenly” lost.
Wed: awoke to 64% (lost one overnight – normal).

I don’t think that this 5% loss is normal - and it’s hard to imagine that ~5kWh of energy has actually been “used” in a couple of hours. Any observations/suggestions ?

Am I worrying over nothing – or should I be making a Service appointment ? Is there even such a thing as a Mobile Service Battery Health Check ?

I can live with a 5% loss – as long as it is only once per cycle. However, if this is just the start of something more serious then I am worried – especially as my warrantee expires … Next Week !

Note - I’ve never charged to 100% before - would doing so perhaps “reset the BMS” ?
What is the current nighttime temperature (in Fahrenheit please). If too cold the car starts up and keeps the batteries from getting too cold
 

MrBadger

Badger out
Jun 17, 2019
9,850
7,530
Surrey, UK
What is the current nighttime temperature (in Fahrenheit please).
As this is a UK and Ireland sub forum, maybe accept it in the units native for that sub forum and do the conversion yourself rather than insisting someone do the conversion for you? Now if someone wants to show both units, then fine, but this is UK and Ireland orientated sub forum so please accept that questions and answers will have a strong UK and Ireland bias.
 
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What is the current nighttime temperature (in Fahrenheit please). If too cold the car starts up and keeps the batteries from getting too cold
My car lives in a comfy garage attached to the house (with a bedroom above). Whilst not heated, it doesn't get quite as cold as outside. I'm guessing the low is currently ~15C - well above freezing.

But these sudden drops are not happening overnight.

And to other comments - I've never seen the %age go up ... not even a single point ... not ever !
 
I've noted this since the 36.5 update that introduced the new energy usage graphical display. Not sure if the update changed anything else related, but I've had drops of 3, 4 and 5% between parking up late morning and driving again next morning. And, 2 nights ago, a reported *increase* of 1%.

So, I'm somewhat unclear on what's happening, but it does seem to be behaving differently to previous versions.
Thanks - good to know.

Although I expect to lose 2 3% every day as "normal" - and I've never seen a gain. I've been seeing 5% go in 2-3 hours !
 
BMS calibrating up and down is a regular thing for our Model 3. They usually balance out over a day or so - easy to monitor on TeslaFi with car left untouched. It’s normally 1 or 2%, but have seen more and as much as 5%.

The other thing this time of year is the cold/blue snowflake icon which not always obvious but can be conformed by adjusting charge level slider to top limit and it stopping at less than 100%.

As for temperatures, it’s not ambient temperatures it’s the temperature of the thermal mass that is the battery. I’ve heard less than 30/35 or so degrees is deemed cold for the battery, which is around 300 Kelvin.

But if it’s a constant drain that never recovers and you are not using sentry or anything else that may stop the car from sleeping then worth investigating further.
 
Last edited:
BMS calibrating up and down is a regular thing for our Model 3.
...

But if it’s a constant drain that never recovers and you are not using sentry or anything else that may stop the car from sleeping then worth investigating further.
As I'm driving an early Model S I don't know that your BMS experience is indicative of my car. And of course I don't even have sentry.

The car has been behaving better over the last couple of days, losing ~1% per 12 hours from Wednesday evening to Friday afternoon, so perhaps it has settled down now. I'll be watching like a hawk over the weekend though !
 
As stated above the BMS has to work very hard to "guess" what's in your battery and coldness reduces the available charge.

Once in a while your car does need to be charged to 100% and once in a while left at less than 20% in order for the BMS to calibrate. If you haven't done that in a while then you might need to help the BMS out.

In very simple terms when the temperature drops the battery voltage drops leading the BMS to believe there is less charge in the battery. (If you flick on the charging screen you will see some of the battery marked as blue - this is capacity that the BMS thinks might be there but can't tell for sure as the temperature and battery voltage has dropped).

The voltage (and indicated capacity) comes back as the temperature of the battery rises but as this is usually due to driving or charging then the effect is masked (and additionally because it is cold and energy is being used to heat the cabin)
 
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As this is a UK and Ireland sub forum, maybe accept it in the units native for that sub forum and do the conversion yourself rather than insisting someone do the conversion for you? Now if someone wants to show both units, then fine, but this is UK and Ireland orientated sub forum so please accept that questions and answers will have a strong UK and Ireland bias
I did say please. Fine. If it gets cold your batteries will get "upset" and use whatever charge it has to warm the batteries up. And since you didn't give me the Celsius temperature In the US most newer cars have this little blue snowflake when the temperature hits 37F (that would be -3C - see how easy that was?).
So if it gets colder than that you WILL lose range.
 
My car lives "indoors" and so never gets really cold - I've certainly never seen a blue snowflake on the display.

So far this cold season even the outdoor lows have only been about 9C - well above 37F (which is PLUS 3C) .

I don't know what I saw, but I don't think that it is an extreme cold triggered event.
Leave it outside next time is gets cold and check it in upper left hand corner. My Prius did the same thing and my wife's 2019 RX350 does
 
Isn't there 8 years of warranty on the battery and drivetrain? A 2016 car is only 6 years old and your mileage is quite low - so another 2 years or whatever the mileage is your warranty indicates.
I bought the car as used (direct from Tesla) in November 2018, with a four year warrantee. AIUI the original battery warrantee doesn't apply to me - even with ultra-low mileage :eek:(
 
Well, that's a bummer. You would have thought if they provide 8 years of warranty on the battery, they would honour that as a matter of course and only provide additional warranty if they are selling a used vehicle that is close to the expiry date of warranty or perhaps have high mileage.
So, if you had bought the vehicle privately, they would honour the entire 8 years but if they sell it, they give you less - that doesn't sound fair at all especially as a private sale would have cost you a lot less.

What does sound fair is Tesla providing the 4 year warranty on the whole car from the date you purchased it and you keeping the original 5 years on the restraints system and 8 years or the stated mileage on the battery and drivetrain. You say "As I Understand It" have you had that clarified?

Have you tried to strike up a conversation with them and raise these points? If you don't ask you don't get but what do you have to lose? Give it a go.
 

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