HV Battery Died with 7 miles range left showing on Range display

[AlanSubie4Life]

Results from service appointment. Summary: Tesla took no action during the appointment, told me the battery is fine and tried to explain that basically the range indicator isn't reliable. I went there, talked to someone for 10 mins and then I left with the car. Car was never seen by Tesla.

The employee said there is no service they can perform. They said they already remotely diagnosed the battery and there were no faults. I asked them if they could do a more comprehensive assessment by for example plugging into the OBD and he basically said there is nothing else they can do that would yield additional information.

This begs the question when their remote assessment does show a fault, what do they do to further investigate?

I received a convoluted speech about how the range indicator is an estimate that varies often, etc. He kept referencing the “15V” low voltage system and made it seem like that played a role in the shutdown which did not make sense to me. No mention of the BMS.

There was no acknowledgment from Tesla that the range indicator was incorrect. It was basically, battery is fine, range is an estimate, don’t take your battery below 10%, have a nice day.

Pretty disappointing.

The good news is this problem which is not normal will probably get worse.

I would report this issue to service as the car shutting down without any warning (according to your information anyway, though I assume it did warn you about low charge levels in general). It’s not really related to how many miles you have left, and would not talk about that next time it happens.

Definitely post next time you get stuck.

Also it would be interesting to get more info on the specific cases in question, as discussed. Was it a continuous discharge from 20% (after car was allowed to sleep), or from 60-80%?

Probably makes a difference, given apparent BMS estimate jumpiness at the moment.

It’s very common for people to target 5% arrival, and drive fast to hit that target, and this shutdown was very close to that. Usually a bit more optimal to arrive slightly higher since charging is slow at very low voltage, but still…

 

[jcanoe]

Results from some extreme range tests done in 2020 and 2021 of the Long Range Model Y showed the Tesla Long Range Model Y could travel an additional 10 to 12 miles after the indicated range was 0 miles. If this is no longer the case then perhaps Tesla Model Y owners should consider ~5% SOC as 0 miles of range remaining.

 

[AlanSubie4Life]

If this is no longer the case then perhaps Tesla Model Y owners should consider ~5% SOC as 0 miles of range remaining.

Yeah, hard to know. I suspect there is just something wrong with this car. But could also be bugginess.

 

[arbitrage000]

Results from some extreme range tests done in 2020 and 2021 of the Long Range Model Y showed the Tesla Long Range Model Y could travel an additional 10 to 12 miles after the indicated range was 0 miles. If this is no longer the case then perhaps Tesla Model Y owners should consider ~5% SOC as 0 miles of range remaining.

Yeah, Teslas should still have some buffer below zero. In that video I posted a couple pages ago, Bjorn got 33km after 0%.
I don't think the OP's situation is normal even if Tesla says it is.

 

[Mikedrives]

I think L-ion SOC accuracy is around 1%

FWIW, I heard from my local phone repair guy that SOC accuracy gets worse at the bottom of the range, AND as the battery ages, making for a compounding effect…
That said, the one time that extreme cold sucked the last 15 miles of range out of our reading within 4 hours while it was sitting, I got it to a home charger and it charged for about half an hour (adding 34 miles of range per hour) before going from 0 to 1 mile of range and then upwards.

 

[Ctuna]

Anybody do battery research before buying one of these .
Try getting a free subscription to reccurentauto.com to learn
something about battery health and keeping your battery healthy.
Free monthly reports on battery health and a lot of education.

 

[ewoodrick]

Anybody do battery research before buying one of these .
Try getting a free subscription to reccurentauto.com to learn
something about battery health and keeping your battery healthy.
Free monthly reports on battery health and a lot of education.

There are libraries of research on batteries.
And the way to determine how to keep your battery healthy is dependent on the chemistry, construction, and use of the battery.
Tesla has used a number of different construction techniques and battery chemistries over the years. There's three (or more) different major chemistries in use today, depends on the specific car and where it was made.

So, listen to the battery experts who have designed the specific Tesla batteries.

A lot of that knowledge is designed into the car, how cool to keep them, how fast to charge them, how much to charge them to, etc.

Just listen to the car is all you need to do. It will tell you.

 

[yellowr6]

did a test a few days ago and see how many kWh usable battery I have in my 2022 MYP with 25k miles. Charged to 100% and drive it to 0% after a few days. under 5%, u can feel the car losing power but not liked the car was shutting off. I got it down to 0% and I can feel the car can still go maybe 10-15 miles.

I juiced it back up to 100% and I have 74 kWh.

 

[Leonard68]

Why would you push it that close?

 

[yellowr6]

curiosity!


so I continue my range testing the following days. Here's my data (with 19" martian wheelset)

74 kwh, i drove 295 miles

79 kwh (what ppl said usable when new), 318 miles

82 kwh battery pack (new*), 330 miles

so yea, u can get EPA! it really depend on how u drive, where u drive, elevation, what u carrying...and many more factors. lol. U just need to avg 250 wh/mi.


if anyone wonder. Im from the Sf Bay Area. 45-60 F degree lately. Mix driving, 50/50 street/hwy. 5-10 miles over limit. Standard mode. Family of 3. Model Y Performance with 25k miles and sitting on 19" Martian wheels with Michelin pilot sport 4 summer tires with 15k miles. And 42 PSI cold.

Im pretty happy with my result. Always in my mind can a MY get EPA if I really try. My avg wh/mi on the 19" martian is 265. This is combination of everything. Some fun here and there when solo. But caution with family.

 

[HMHM]

When you park your Model Y at the Home location is Sentry mode set to be Off. When Sentry mode remains active, at the Home location the Telsa Model Y cannot enter sleep mode. The Tesla Model Y's battery management system can only measure the open cell voltage (OCV) of the cells in the high voltage battery when the high voltage battery is disconnected as during Sleep mode. The OCV measurement improves the BMS's ability to accurately determine the state of charge of the battery.

I'm disheartened to learn that the Tesla BMS has some shortcomings. I would think, amongst all the vital parameters it's supposed to manage, an accurate measurement of SoC would be a top priority. Furthermore, battery calibration should be happening without any OP intervention. If OCV is needed for calibration, the BMS should have an inbuilt capability to get that reading. I'm also wondering about the buffer. Whatever happened to the hidden 20 mi buffer at 0% SoC?

 

[wk057]

Whatever happened to the hidden 20 mi buffer at 0% SoC?

There was never any usable buffer below 0%. Never. Not on any Tesla vehicle.

Anecdotal reports of some folks able to drive below 0% are pure luck. If you're able to drive below 0%, it means the BMS was being overly conservative due to one or more conditions that prevented it from accurately calculating energy available, meaning 0% wasn't actually what it expected it to be. Instead, it would allow usage until the actual measured parameters were 0%, potentially giving a little bit of driving below 0%. This is exactly how the BMS should behave, also. It's ok if an error has range below 0%. It's not ok if an error puts real 0% at a positive display percentage.

Any energy below 0% is the exception, not the rule. 0% means 0%, and you should never expect any usable capacity below 0%.

 

[ewoodrick]

I'm disheartened to learn that the Tesla BMS has some shortcomings. I would think, amongst all the vital parameters it's supposed to manage, an accurate measurement of SoC would be a top priority. Furthermore, battery calibration should be happening without any OP intervention. If OCV is needed for calibration, the BMS should have an inbuilt capability to get that reading. I'm also wondering about the buffer. Whatever happened to the hidden 20 mi buffer at 0% SoC?

Batteries are partially science, but a big part black magic.

There are NO BMS solutions that are perfect. The only time that they can get close is if you use the same load every day and charge identically and it's the same temperature. So beyond that is where the black magic comes into place..

the battery calibration DOES happen without user intervention, but again, it's not perfect.

 

[HMHM]

Batteries are partially science, but a big part black magic.

There are NO BMS solutions that are perfect. The only time that they can get close is if you use the same load every day and charge identically and it's the same temperature. So beyond that is where the black magic comes into place..

the battery calibration DOES happen without user intervention, but again, it's not perfect.

Battery technology is going through a very fast evolution. Tesla had a wonderful head start, but many well known shortcomings have not been a priority at Tesla for reasons unknown. All I'm doing is highlighting the issues. The battery calibration is driven by the BMS, and it can become better and more efficient.

 

[HMHM]

There was never any usable buffer below 0%. Never. Not on any Tesla vehicle.

If that is the case, then why Tesla and their vendor partners are silent to see the likes of Edmunds and other renowned auto media publishers extensively tout about this hidden buffer in all their reviews? My fear is that in case of a true emergency, it can be a life and death issue, and a liability issue. Tesla is no fool! They should be warning consumers about this lie aggressively.

In my opinion, there is some truth about that hidden buffer. You would not design a BMS without a buffer. Otherwise, Tesla BMS is a poor battery management system, or just a thermal management system.

Tesla sets the cutoff voltage parameter in the BMS, which triggers the vehicle power shutdown. As promoted and reiterated by most of the media outlets, this cutoff is generally about 20 miles after the 0% SoC. In this case, it was a very poor performance of the BMS that it fell way short because it could not accurately account for the SoC, operating voltage, and overall battery health. This is a totally unacceptable situation.

 

[MP3Mike]

You would not design a BMS without a buffer.

Only companies actually do. Look at the Zero mile results in Bjorn's tests: https://docs.google.com/spreadsheets/u/0/d/1V6ucyFGKWuSQzvI8lMzvvWJHrBS82echMVJH37kwgjE/htmlview

There are 3 with zero, or negative, buffer... But keep in mind that the results are not guaranteed and can vary with each test.

 

[avs007]

Bjorn mentioned that a lot of times the below zero buffer also served to hide degradation, as the buffer would shrink as the battery aged.

 

[HMHM]

Only companies actually do. Look at the Zero mile results in Bjorn's tests: https://docs.google.com/spreadsheets/u/0/d/1V6ucyFGKWuSQzvI8lMzvvWJHrBS82echMVJH37kwgjE/htmlview

There are 3 with zero, or negative, buffer... But keep in mind that the results are not guaranteed and can vary with each test.

Yeah, Teslas should still have some buffer below zero. In that video I posted a couple pages ago, Bjorn got 33km after 0%.

A buffer is a must!

 

[wk057]

Hidden capacity below 0% would be for people who don't know how to read their dash. 0 means 0. If it says 15 miles left and you try to go 25, and you don't make it... that's not the car's fault. That's the driver's fault. If it says 15 and it dies after 5 miles and shows 10 left but won't drive, that's the car's fault.

If you can't understand that 0 means 0, then you shouldn't be driving.

 

[ewoodrick]

Battery technology is going through a very fast evolution. Tesla had a wonderful head start, but many well known shortcomings have not been a priority at Tesla for reasons unknown. All I'm doing is highlighting the issues. The battery calibration is driven by the BMS, and it can become better and more efficient.

You do realize that Battery Management Systems have been around for o 50 years don't you?
I remember NiCads in devices that I got in the '70s. They had their own BMS.