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85d battery deteriorating
- Thread starter Bobesla
- Start date
Not quite, still in preliminary information gathering stage. Per LA Times:
Federal safety agency launches probe of Tesla battery fires
Per the NHTSA itself, Tesla is being investigated under NHTSA Investigation number DP19005 and Tesla will face punishment for failure to cooperate with an ongoing federal investigation if they fail to cooperate with this investigation directly pursuant to 49 USC 30166 which authorizes NHTSA to conduct any investigation that may be necessary to enforce Chapter 301 of Title 49. They have not been served with "information gathering" word play, they are under legal obligation to comply with federal laws regarding NHTSA investigation DP19005 as of now.
If wordplay was all it took to avoid federal investigations, Tesla wouldn't be the first to try that tactic. We can pretend pedantic wordplay might make the investigation unreal, but we can't pretend t\nothing will happen if Tesla refuses to cooperate with the investigation.
Tesla is under federal investigation, pedantically or not it's the actual dictionary definition of the word.
whitex
Well-Known Member
Search TMC. This information comes from reading out the BMS (Battery Management System) via CAN bus which a number of people have done (you can find how to do it youself using a CAN bus reader and some crowd sourced software people have written after some reverse engineering). It also shows up when the car is put in diagnostics mode (which Tesla service tech can do, or some people have hacked their cars to enable it).
The numbers I gave you came from other P85D's, not mine specifically.
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aerodyne
2 of 3 EV's - Defect Free!
Searching this board, lots of info. The 85 pack has about 77.5 Kwh available when new. The 100% rated range is 265 - 270.
Teslafi or other apps can give you updated rated range and degradation after every charge, and the Kwh going into the pack.
Using this info, my EPA consumption, not including charging losses is 292 Wh/mi. My actual usage over the last year/6k miles is 297 Wh/mi per the car.
Range has varied from 272 to 264, due to storage for months and seldom go above 70% or below 30%. When I do go above 70, the car recalibrates. No need to go above 90% or below 20%.
aerodyne
2 of 3 EV's - Defect Free!
Depends what you call rough. Since on my case, the BMS predicted range has never been more than 3% away from the EPA range, I'd say that is pretty accurate over 4 yrs/30k miles
whitex
Well-Known Member
Search for posts by wk057, BMS does report nominal capacity (same for all 85 batteries for example). Any current SoC is of course always an estimate.
You don't get the point. Predicted range equals usable kWh remaining multiplied EPA range. So it has to be spot on. But the actual usable kWh is pure BMS estimation. Unless you discharge the battery slowly to BMS shut down voltage and charge it back to 100%. So any assumptions based on BMS estimation numbers are simply far away from the reality.
whitex
Well-Known Member
Correct. I was stating what the nominal capacity was. My personal car stated deterioration is very small based on my observation that 90% has been charging to the same rated miles since new (might have lost 1 mile) for the last 4.5 years.
aerodyne
2 of 3 EV's - Defect Free!
Using data from trip computer and Teslafi, I find that my Kwh used (30+) divided by miles traveled on long trips has never been more than 10% different than rated, unless cold weather, etc. Same applies to estimated battery % during a trip, compared with actual used.
Of course, the BMS is an estimate. But MY point is it is a pretty accurate one, as other factors, such as road conditions, driving style, speed, winds, HVAC, can easily cause more than 10% variation.
Sorry, but this is a false statement. There is zero relation between battery degradation and rated miles at 90%. As I said, rated miles at 90% are based on the usable kWh value reported by BMS. You can do a simple test. Deplete the battery by driving and then let it discharge by running cabin heating till the car shuts down. Then charge it to 100%. First after doing this, the BMS will know, how much energy was pumped into the battery and will update your nominal capacity and rated miles at 90%.
whitex
Well-Known Member
Ok, if you are right and there is in fact zero relation between rated miles and degradation, then people who see their 90% dropping have nothing to worry about, it doesn't mean anything about degradation, right? I think many of those people would disagree.
As for it being an estimate, you are correct. I've worked on battery systems (not for cars, but for phonesm tablets, etc, for over a decade) so of course ALL SoC are estimates, even 100% KWh is only an estimate (i.e. the percentage is not an estimate, but how many Wh you can pull out of it is a total estimate).
It is not 'far away from reality'. The BMS is extremely good at calculating and estimating battery capacity. Yes there is no way to directly measure the capacity. The only direct way is to discharge it and see how much you got out. But that doesn't mean the BMS isn't accurate using other methods to estimate it. Based on my experience it is very accurate. Definitely accurate enough to keep track of degradaion over time.
So its very accurate but you actually never completely discharged and charged the battery to be able to confirm it. So again, how do you know that it is accurate? Or did I miss some other way how do you confirm the available (nominal or usable) capacity?
I have discharged my battery down to 0 miles left and charged it up to 100%. I do this regularly. The BMS has a very good estimate. It is able to make such a good estimate based on many years of data collected from Tesla and fed into an AI system. The BMW is far more sophisticated than just looking at a few numbers. Again, you are right it cannot measure capacity directly, but that doesn't mean it is bad at making an accurate estimate. That's the whole point. I have watched the BMW dong it's work on my car (and other) for years looking at the CAN bus data. It is stunningly accurate.
It's complicated. And there are multiple schools of thought.
I think that Tesla's position is that the batter is built so that you don't have to worry about it. Their calculations and warranties take all sorts of battery regimens into account and you they are still estimating 300,000 mile range of the Model 3.
That said, they have suggested that continuous charging to 100% isn't optimal, as long as you drop it below 90%, life should be good.
Now, from that, there's all sorts of FUD, misinformation, bad information, and wrong information floating around.
The batteries in the Model S/X and the Model 3 are different and in the S/X there have been multiple formulations over the years.
Batteries can be optimized for longevity, capacity, charge rate, temperature and a number of other variables. As with many things, you make one variable better, the others often suffer. Many of the studies that people reference are often based upon generic cells, cells that are designed for other purposes and often with different criteria. Cellphone batteries are one example that many studies are built upon and have very different goals 2-3 years is all that is needed, it's capacity and weight.
Tesla hasn't released that much on the batteries, so there really isn't a lot of information out there.
Okay, so why do I make the suggestions that I do?
First, there are hundreds of "my battery is degrading posts" and none of them really are. Battery capacity calculations are guesses and there are a number of factors that go into the calculation, so it's all pretty bogus to begin with. You'll find that out during your first winter.
Allowing batteries to balance their charge is helpful for the battery pack. If one battery has a lower voltage, then the pack has a lower voltage and all sorts of things aren't optimal. My engineering tells me that the batteries aren't going to equalize well until they are all at max voltage which equates to 100% charged. That also seem to be a point in which the car recalculates max charge and brings the max back to a more realistic guesstimate. You really can only know when a battery is fully charged after you pour current into it and it doesn't accept anymore.
Keeping it at 70% has been proven will result in estimations that vary from reality. That's what causes many people to start complaining.
Charging to 100% helps fix this and doesn't damage the battery. The battery was built to be able to charge to 100%. Matter of fact some of the highest mileage cars regularly charge on Superchargers and near 100%.
Every few months going to 100%, well, first, get out of the house, take some trips and enjoy life. Charge to 100% when you do and everything is better.
aerodyne
2 of 3 EV's - Defect Free!
Yes, I agree it is complicated, and V9 and V10 changes to the BMS limits may have made things even more so, on some cars, while others, are not affected...
From Elon's tweets, given in the time frame of the Gen One 18650 cell production, operating the car mainly from 30-70% SoC will enhance the chance of the battery lasting a long time, say 20 years,
When storing the car, he suggested to keep the SoC between 50 and 62%.
These guidances are qualitative, and do not give any quantitative measure as to how effective they will be.
My experience is the BMS is always calibrating, and in my case, even after months of storage at 55 to 52% , RM was only off by a percent or so. Charging to 80 and driving down to 40 brought the RM right up.
I tried once after V9 to go to 100% SoC at a SuC. Car did not seem happy above 95% with the fans running full blast, 30 min gave up at 99%. I won't do that again, only picked up one RM in the process. I don't want to get tagged by the Mothership for a future "update"
I have Teslafi and it does a real good job of reporting data and battery estimates.
I will still get out of the house and enjoy life, but only with 95 or less percent....
From Elon's tweets, given in the time frame of the Gen One 18650 cell production, operating the car mainly from 30-70% SoC will enhance the chance of the battery lasting a long time, say 20 years,
When storing the car, he suggested to keep the SoC between 50 and 62%.
These guidances are qualitative, and do not give any quantitative measure as to how effective they will be.
My experience is the BMS is always calibrating, and in my case, even after months of storage at 55 to 52% , RM was only off by a percent or so. Charging to 80 and driving down to 40 brought the RM right up.
I tried once after V9 to go to 100% SoC at a SuC. Car did not seem happy above 95% with the fans running full blast, 30 min gave up at 99%. I won't do that again, only picked up one RM in the process. I don't want to get tagged by the Mothership for a future "update"
I have Teslafi and it does a real good job of reporting data and battery estimates.
I will still get out of the house and enjoy life, but only with 95 or less percent....
Dang, those rates are slow. For those folks that don’t remember what “new” was like on an 85 pack I recommend checking out this video:
