# How do we Determine REAL degradation?



## FRC (Aug 4, 2018)

Thanks to several of our curious and learned fellow forum members, we now know that the bulk of the reduction shown on our range display is the result of an unbalanced battery. And there are several threads here covering the Battery Management System and rebalancing the battery.

But some of the reduction that we see is actual degradation. This would be the reduction in the displayed range that cannot be rebalanced or recovered. It's range that is lost forever. And this is the number that I think we would all like to know definitively.

Is there a way for the average owner to define their actual degradation? I can balance and balance and balance until I can't seem to recover any additional range. So is the remaining range loss my degradation? How do I know for certain that my battery is fully balanced? I guess what I'd like to see is a gauge that tells me that my battery is 95% or 97% or 100% balanced. Is this even possible? Could it be achieved via a software update?

Obviously, I have lots of questions about this that my feeble brain cannot answer! Do those of you that are smarter than me(and that includes almost everyone) have the answers?


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## TomT (Apr 1, 2019)

A question that has been asked since the birth of EVs (at least those of 21st Century vintage) and still remains unsatisfactorily answered... The Leaf capacity meter and aftermarket tools came the closest (possibly because the Leaf suffered horrendous capacity loss)...


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## JWardell (May 9, 2016)

FRC said:


> I guess what I'd like to see is a gauge that tells me that my battery is 95% or 97% or 100% balanced. Is this even possible? Could it be achieved via a software update?


You can certainly display your battery balanced percentage on a display, but that has nothing to do with degradation or health of your pack, it's just a temporary difference between multiple batteries. (But still of interest, and, well, I'm working on it)

The true capacity of a pack can only be determined by fully charging and discharging it while measuring energy in and out, often repeated for days or weeks, with a couple hundred thousand dollars of equipment. Then repeat that a few times I year ago to know your true battery health over time?

That's what the BMS attempts to do to watch battery consumption and make a somewhat educated guess of it's capacity and state of health. Easy if you have a nice constant charge and discharge rate. Next to impossible when your discharge load is widely varying and spiking as is normal when driving.

The Teslafi graphs are still the easiest/best way to track battery capacity over time, as long as you have the understanding that it is not a hard number and the result of a lot of guessing. But it's now summer and I've gone on some long trips, and my pack hasn't come back up, so maybe I can put a bit more faith in my lower range number. But there's always hope


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## FRC (Aug 4, 2018)

JWardell said:


> You can certainly display your battery balanced percentage on a display, but that has nothing to do with degradation or health of your pack, it's just a temporary difference between multiple batteries. (But still of interest, and, well, I'm working on it)
> 
> The true capacity of a pack can only be determined by fully charging and discharging it while measuring energy in and out, often repeated for days or weeks, with a couple hundred thousand dollars of equipment. Then repeat that a few times I year ago to know your true battery health over time?
> 
> ...


But it appears to me that the Teslafi info shows the TOTAL range lost to battery imbalance(temporary loss) AND degradation(permanent loss). These two issues are completely separate and unrelated and combining the two results in useless information(it seems to me). Is there not a reasonable way to separate and communicate these numbers?


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## Ed Woodrick (May 26, 2018)

Best way to solve the problem?

Just don't worry about it. Assume a couple percent per year and be happy if it is less.

The only time it matters is when it starts to get down around 70%. And that becomes evident when you charge to 100% and you travel 50% of your distance and you have only a few percent left.


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## FRC (Aug 4, 2018)

Ed Woodrick said:


> The only time it matters is when it starts to get down around 70%.


This is where it becomes REALLY important, and is part of the reason for the thread. Let's imagine that as the battery warranty period nears expiration(120K miles in my case), my displayed range begins to dip below the warranted 70%(310x.7=217, for me). How can I determine whether I should be covered by the warranty or not, and further, how can Tesla prove that my issue is balancing and not degradation. Unless you believe that Tesla will encounter 0 battery range warranty issues(I don't), then someone will be put in a position of proving that their battery has not performed as warranted. Exactly how can that be done? I'm not stressed about it at all, I would just like to know how this issue might be handled.


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## kornerz (Sep 27, 2017)

FRC said:


> How can I determine whether I should be covered by the warranty or not, and further, how can Tesla prove that my issue is balancing and not degradation. Unless you believe that Tesla will encounter 0 battery range warranty issues(I don't), then someone will be put in a position of proving that their battery has not performed as warranted. Exactly how can that be done? I'm not stressed about it at all, I would just like to know how this issue might be handled.


Balancing-related capacity loss is rarely more than 0.3 kWh, so if range (as shown in Tesla app charge screen at 100%) degrades more than by a couple of percents in warm weather (20C and more), it is degradation and not balancing.

I've compared said Tesla app output with TeslaFi data and the real data (battery capacity value from CAN bus), and they match within 0.1 kWh of battery capacity.


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## garsh (Apr 4, 2016)

FRC said:


> Is there not a reasonable way to separate and communicate these numbers?


If Tesla were able to accurately determine that, then we probably wouldn't need to rebalance the battery because they'd be able to simply display a better capacity guess.


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## shareef777 (Mar 10, 2019)

FRC said:


> This is where it becomes REALLY important, and is part of the reason for the thread. Let's imagine that as the battery warranty period nears expiration(120K miles in my case), my displayed range begins to dip below the warranted 70%(310x.7=217, for me). How can I determine whether I should be covered by the warranty or not, and further, how can Tesla prove that my issue is balancing and not degradation. Unless you believe that Tesla will encounter 0 battery range warranty issues(I don't), then someone will be put in a position of proving that their battery has not performed as warranted. Exactly how can that be done? I'm not stressed about it at all, I would just like to know how this issue might be handled.


My guess is that if the displayed range ever shows 217mi at 100%, you let it drain and charge it back up. If it's still 217mi, file a warranty claim and Tesla will take care of it. Based off of what I've seen it's more likely that we'll all be in the 80-90% range and Tesla just dropped another 10% in coverage to avoid a large number of warranty claims.


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## JWardell (May 9, 2016)

FRC said:


> But it appears to me that the Teslafi info shows the TOTAL range lost to battery imbalance(temporary loss) AND degradation(permanent loss). These two issues are completely separate and unrelated and combining the two results in useless information(it seems to me). Is there not a reasonable way to separate and communicate these numbers?


True. But I've seen no evidence of battery imbalance being more than a few mV or anything significant for Model 3. But you could for example just do the math of imbalance voltage over total voltage range and correct the estimated range by that. (If your battery's limits are 2.8 to 4.2V, a 6mV imbalance is 0.4% of its capacity*)

*with a linear battery derating curve, which it is not in reality


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## FRC (Aug 4, 2018)

JWardell said:


> True. But I've seen no evidence of battery imbalance being more than a few mV or anything significant for Model 3. But you could for example just do the math of imbalance voltage over total voltage range and correct the estimated range by that. (If your battery's limits are 2.8 to 4.2V, a 6mV imbalance is 0.4% of its capacity*)
> 
> *with a linear battery derating curve, which it is not in reality


Now allow me to parade my ignorance for all to admire. We continue to see reports of the range reported by Teslafi and from owner's calculations to improve considerably(as much as 5-7%) by methods to balance the pack. But now you and @kornerz say that displayed range loss from an imbalanced battery is insignificant. And you both use lots of fancy terms that I don't understand that lead me to believe that you know what you're talking about. I can only assume that one of us misunderstands what the other is saying. What gives?


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## JWardell (May 9, 2016)

FRC said:


> Now allow me to parade my ignorance for all to admire. We continue to see reports of the range reported by Teslafi and from owner's calculations to improve considerably(as much as 5-7%) by methods to balance the pack. But now you and @kornerz say that displayed range loss from an imbalanced battery is insignificant. And you both use lots of fancy terms that I don't understand that lead me to believe that you know what you're talking about. I can only assume that one of us misunderstands what the other is saying. What gives?


Haha. Of course this is highly technical stuff. Which is why most (really everyone) should really not stress about it.
The range reported by your car, and used by TeslaFi for the battery graph (as well as the full pack nominal capacity CAN signal) is mostly the result of a bunch of code that does its best to measure and watch the battery over time to guess at how much its capacity is. A small portion of that is due to possible imbalance, but in practice I've only seen very small imbalances in Model 3 packs. It is half of our advice (charge to 90 and let it sit, or the charge to 100 folks), but only because it's the easier thing to do to remove unbalance uncertainty from the equation. Discharging most of your battery on a long constant-load drive is where most of the range equation gets its data.

And the biggest reason why it bothers to do this is to tell you your battery is near dead BEFORE it is dead. It's actually very hard to do. If you had it right 99% of the time, then every hundred drives down to a few miles/percent, you would be stranded. That is not acceptable. So it HAS to err on the lower-range/capacity side.


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## garsh (Apr 4, 2016)

JWardell said:


> And the biggest reason why it bothers to do this is to tell you your battery is near dead BEFORE it is dead. It's actually very hard to do. If you had it right 99% of the time, then every hundred drives down to a few miles/percent, you would be stranded. That is not acceptable. So it HAS to err on the lower-range/capacity side.


Ah, yes. That reminds me of Ian's story about driving back on his cross-Canada trip. This is what can happen when your pack is unbalanced (from a lot of aggressive supercharging) and the BMS gets VERY confused. Click through to read the entire story, but I've included the relevant portion here.


Mad Hungarian said:


> Trev and I were tootling along with around 11% or 12% left and only 18 km / 12 miles to go to the SC in Saint-Leonard NB when suddenly as we were cruising up a hill on Autopilot at around 120 km/h / 75 mph the speedo started to drop. This was to say the least alarming, because when the car starts to struggle going up a fairly normal highway incline you are usually just minutes away from it shutting down. And we still had a ways to go.
> Thankfully I remembered the words of wisdom from @Out of Spec Motoring that when you sense the car seriously starting to pull back power it's absolutely critical not to stress it out, as any sudden drop in voltage below what the BMS considers critical in just a few of the cells will cause the whole pack to shut down. But if you cruise along very carefully at the minimum safe speed, using only the lightest possible pressure on the accelerator to keep the car moving, you can eek out quite a few more miles. Which we thankfully did, and made it. But juuuusssst barely. By the time we reached the SC the car's top speed was down 50 km/h / 32 mph and I don't think we would have gone much more than another mile, if even that.
> Here's the frightening part: *The screen still showed 8% left*
> Yes, you read that correctly.
> ...


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## Ed Woodrick (May 26, 2018)

FRC said:


> This is where it becomes REALLY important, and is part of the reason for the thread. Let's imagine that as the battery warranty period nears expiration(120K miles in my case), my displayed range begins to dip below the warranted 70%(310x.7=217, for me). How can I determine whether I should be covered by the warranty or not, and further, how can Tesla prove that my issue is balancing and not degradation. Unless you believe that Tesla will encounter 0 battery range warranty issues(I don't), then someone will be put in a position of proving that their battery has not performed as warranted. Exactly how can that be done? I'm not stressed about it at all, I would just like to know how this issue might be handled.


It doesn't really matter what you figure out. If I remember the warranty, the process is completely up to Tesla to make the determination. 
It will become REALLY obvious when you actually have significant real degradation and that's probably what Tesla is going to look at. That's when you charge to 100% and can't get the range by actually driving it. Forget the meters, forget the third party apps, you have to drive the car.

For those of us with other EVs that only had around 100 miles range, it becomes obvious when degradation has kicked in. If on a 100 mile battery in winter and at full charge I can't drive 30 miles, then the battery is a problem.

Tesla has seemed to be pretty decent about replacing batteries when needed, or more specifically I haven't seen any/many thread with complaining about the batteries not being replaced. And that's with the Model S and some X. I haven't seen much of anything on the Model 3 batteries.

Folks, Tesla has come a LONG way with their batteries, stop assuming that what happened on a battery 7 years ago is what is going to happen to your battery. The big issue with batteries, across essentially all manufacturers is pretty much behind us now.

Chill, ignore the battery, enjoy the car.


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## JWardell (May 9, 2016)

garsh said:


> Ah, yes. That reminds me of Ian's story about driving back on his cross-Canada trip. This is what can happen when your pack is unbalanced (from a lot of aggressive supercharging) and the BMS gets VERY confused. Click through to read the entire story, but I've included the relevant portion here.


I would really love to have known how imbalanced @Mad Hungarian 's pack was at that point. It was certainly worst case, with LOTS of supercharging..the faster you charge, the more different internal resistances of each cell throw them out of balance....and a SHORT time between charges...the car needs sometimes DAYS to bleed off that imbalance, and it never had the chance on his continuous trip. Would certainly have made a great data point. But it also shows it appears at least at the time tesla was not compensating for that imbalance, and now you have a dangerous situation which the range says things are A-OK. Perhaps more recently Tesla has started taking that into consideration, and that's why we've seen some reduction of range.

On a side note, I noticed my Teslafi Battery Report graph actually stopped updating in December. No wonder mine hasn't got any better! I was able to use the search instead to graph 2020 and it did improve with rising temperatures as I had always predicted, but then fell drastically when it was barely getting driven and charged. And now I can't get Teslafi to graph lifetime anymore...hmm something is broken there. Anyone else notice this?


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## bwilson4web (Mar 4, 2019)

Just learned about:
https://www.recurrentauto.com

_Monthly Battery Reports_​​_Get a free personalized monthly battery analysis of your EV while helping accelerate the adoption of EVs everywhere._​
I'm skeptical of "free" anything. Just wondering if anyone has tried this group?

Perhaps someone might do a compare and contrast with existing tools.

Bob Wilson


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## littlD (Apr 17, 2016)

bwilson4web said:


> Just learned about:
> https://www.recurrentauto.com
> 
> _Monthly Battery Reports_​​_Get a free personalized monthly battery analysis of your EV while helping accelerate the adoption of EVs everywhere._​
> ...


I signed up Middie and Middy on this.

We'll see what's what but I'm not holding my breath that they'll get anything more than just "Estimated Range" from the Tesla API, which is what TeslaFI uses.


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## sduck (Nov 23, 2017)

For some reason I can't recall I signed up for Recurrent. As above, it's the same data teslafi uses, just presented a little differently. Here's what one of their reports looks like. Not a typical month for me, very little driving as I was furloughed and back in quarantine mode, no road trips or anything.


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## kornerz (Sep 27, 2017)

Another data point on battery degradation.

Here is a graph of actual battery capacity in kWh over the past year, obtained from CAN bus logging, from my 2019 SR+:








In October I've though "that's it, battery degradation kicked in" with 48kWh of capacity remaining.
However, now it is slowly crawling back, 49.7 currently - so it is hard to determine if battery degraded even if you have access to actual capacity data the car provides.


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## Ed Woodrick (May 26, 2018)

kornerz said:


> Another data point on battery degradation.
> 
> Here is a graph of actual battery capacity in kWh over the past year, obtained from CAN bus logging, from my 2019 SR+:
> 
> ...


So it seems obvious that you aren't looking at battery degradation. Degradation should only be a descending line.


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## kornerz (Sep 27, 2017)

Ed Woodrick said:


> So it seems obvious that you aren't looking at battery degradation. Degradation should only be a descending line.


Or I have less than 1% of degradation, which is not visible over "regular" fluctuations of full battery size reported.


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## Ed Woodrick (May 26, 2018)

kornerz said:


> Or I have less than 1% of degradation, which is not visible over "regular" fluctuations of full battery size reported.


While indeed a possibility, I don't really trust the data that your graph represents because it is obviously either not exactly what we think that it is or that it is processed by some algorithm that may hide the reality.

But yes, it tends to suggest that you haven't lost much/any and that looking at capacity at any point along the line is not really informative.


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## tencate (Jan 11, 2018)

Interesting discussion. My car is now 3 years old (give or take a week) and has just about 80k miles displayed on the odometer. As far as I can tell, my displayed maximum range is around 300 miles. Tesla sold it to me with a range of 310 so just 10 miles of degradation over 80k miles. Of course, over the lifetime of the car, Tesla has gotten LOTS better at managing the motor and I'm sure the car is way more efficient at using its battery juice than it was when I bought it. So who knows what the real degradation is... and I don't think I care. 

Another obvservation. Early in Max's lifetime, I used the Navigation to charge and I would always charge a bit longer than it suggested to give myself a "range cushion." Why? A few times I ended up arriving at a SC with less than 10% charge displayed (!) and once I ran into a powerful headwind and didn't have enough charge to make it and had to turn around and juice up again. So I always charged longer just in case. This last trip (4200 miles) was different, I never felt the need to charge longer. I used Tesla's Navigation exclusively, stopped charging when it said we were ready to go, and arrived at the next SC with around 50 miles to spare every time.

My new mantra when doing long trips comes as the voice of Obi-wan: "Trust the Navigation Luke, er Jim"


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## JWardell (May 9, 2016)

Ed Woodrick said:


> So it seems obvious that you aren't looking at battery degradation. Degradation should only be a descending line.


In my testing, I find the CAN battery capacity actually aligns with the same range that Teslafi uses for its charts...in other words they are both estimated energy at the moment guesses. It's all estimation by software. The only way to really measure for sure is to hook the pack up to a very expensive battery test system that puts it through multiple charge discharge cycles.


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## r-e-l (Dec 19, 2018)

highly technical discussion that I don't understand much.

here is what I know:

1. Car is now 2 years old (this week)
2. just got to 10000M
3. always been charged at 80%. 
4. When was new - it charged with 237mies left.
5. Now its on 222miles for same so roughly 6% loss.
6. I know at the time when Tesla was able to add 5 miles range it was a big deal... somehow the 15miles seems to be "why even worry about it? just enjoy your car"
7. I know when a new buyer will come to buy it ... he is going to look at this range. He/she might be comparing it to other cars. or might be looking at it as battery degradation. I know I wont be able to explain any of this "don't worry about it, just enjoy the car will probably not work"
8. Am reading here on rebalancing/resetting battery but not clear is this is real thing or urban legend as some other claims.
9. My drives, when I drive, are fairly short (16 miles a day)
10. Car is in garage and temp are around 45f
11. Regular home charge 120V (5Miles an hour)

So I am with the original OP. At a leading EV company, one that does "battery days" event, celebrate how they squeeze another 5 miles into a range ... I wish they can provide a specific guide and if possible (assuming they know what to do) a utility in the car that guide the user what to do. Can be something like smart "maintenance schedule" that says ... times to discharge to X level, time to charge up to Y level.... 

The fact there is nothing official is frustrating.

That being said - anyone can point to the "battery balancing" procedure dont mind trying it out ....


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## garsh (Apr 4, 2016)

r-e-l said:


> 3. always been charged at 80%.
> ...
> 9. My drives, when I drive, are fairly short (16 miles a day)


The BMS (Battery Management System) can sometimes find it difficult to correctly estimate how much energy the battery can hold. Constant supercharging can really throw it out of whack. But also, keeping the state of charge in a very narrow range will cause it to lose accuracy over time. So if your state of charge has been bouncing between 75%-80% for a long time, it could very well be confused.



> That being said - anyone can point to the "battery balancing" procedure dont mind trying it out ....


JWardell outlines the procedure here:


JWardell said:


> So many things affect the range value that your car and Teslafi uses for that plot. It is not a real gauge of your battery's physical condition and degradation. It's a software algorithm that averages tons of parameters over a long period of time, and it doesn't recalibrate all that often. The best thing you can do I switch your gauge over to percent and stop stressing over range.
> 
> Battery balancing will trigger only when over 90% -let's say charge to 92% to be sure, but no need for 95 or higher- and only if the BMS thinks things are out of whack enough to do so. No need to start from 20% or whatever.
> But the calculations and range will not update until after a balance the car then goes for a good drive and gets the battery below 50%.
> ...


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## Ed Woodrick (May 26, 2018)

r-e-l said:


> highly technical discussion that I don't understand much.
> 
> here is what I know:
> 
> ...


That was as far as I needed to read. First, you probably don't have any degradation, you only have degradation in the calculations.

You NEED to charge past 95% to get the calculations to reset and like the battery management system equalize the batteries.

Take a long trip periodically, charge to 100% before you go. That will make your car happier.


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## tencate (Jan 11, 2018)

Ed Woodrick said:


> You NEED to charge past 95% to get the calculations to reset and like the battery management system equalize the batteries.


I've read that in other threads but never actually noticed that making any difference at all on my car. Does anyone have a reference for the "charge above 95% occasionally recommendation) or know something more other than the several anecdotes I've seen on this forum? Or have I missed a thread where the "technicalities" are discussed? Hmmmm, car says it has an update available... later!


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## garsh (Apr 4, 2016)

Ed Woodrick said:


> You NEED to charge past 95% to get the calculations to reset and like the battery management system equalize the batteries.


This is incorrect. You only need to charge past 90%. Charging past 95% is not recommended.


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## r-e-l (Dec 19, 2018)

Thank you @garsh and @Ed Woodrick for the useful tip.

I am happy its not a real battery degradation and its "only a calculation issue" - as long as I can bump it up - am happy. As long as I cant - I not happy and consider it degradation regardless if its due to calculation or a true battery issue.
I am not planning on getting anywhere close to 10% so I will never see (I hope) if those lost 15 miles are true loss or just calculation. But am fairly sure a buyer will care and will look at it as lost mile.

I will give it a try and see how goes....

thanks again!


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## JWardell (May 9, 2016)

garsh said:


> This is incorrect. You only need to charge past 90%. Charging past 95% is not recommended.


Frankly you don't need to charge high at all. Just go for some long drives.
The original requirement for 90% was to trigger balancing, which can now occur at any level. But even that is pointless...
I've been watching balance levels over the past three months. They are always at a microscopic 3-4mV. Most I've seen is 6mV for a few minutes after a supercharge. This was an issue in older (model S?) cars, where balancing would be off by 50-100mV.

Go for a long highway drive of about 50% of your battery or more, then let it sit parked for half an hour. It will probably make a new calibration. 
Repeat that more often and it will continue to improve.
Mine's been terrible because I've barely been driving all year. Than last week I had to make six 1-hour drives for work. Sure enough, range went up each day.

Just drive! Or don't worry about it.


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## r-e-l (Dec 19, 2018)

JWardell said:


> Frankly you don't need to charge high at all. Just go for some long drives.
> The original requirement for 90% was to trigger balancing, which can now occur at any level. But even that is pointless...
> I've been watching balance levels over the past three months. They are always at a microscopic 3-4mV. Most I've seen is 6mV for a few minutes after a supercharge. This was an issue in older (model S?) cars, where balancing would be off by 50-100mV.
> 
> ...


how long is a long drive? I take it that dropping to 50% via many small drives doesn't count ....


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## Ed Woodrick (May 26, 2018)

JWardell said:


> Frankly you don't need to charge high at all. Just go for some long drives.
> The original requirement for 90% was to trigger balancing, which can now occur at any level. But even that is pointless...
> I've been watching balance levels over the past three months. They are always at a microscopic 3-4mV. Most I've seen is 6mV for a few minutes after a supercharge. This was an issue in older (model S?) cars, where balancing would be off by 50-100mV.
> 
> ...


Wasn't it Elon who mentioned that you need to go to about 95%?


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## Ed Woodrick (May 26, 2018)

garsh said:


> This is incorrect. You only need to charge past 90%. Charging past 95% is not recommended.


Pretty sure that charging to 100% is in the book for when you take trips.

Taking long trips is something that the car expects you to do.


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## tencate (Jan 11, 2018)

Ed Woodrick said:


> Pretty sure that charging to 100% is in the book


Should be easy to check, no? I'll look through the manual today. Haven't done that in a while. If I find something, I'll post it. If not, see if you can find that Elon Tweet you mentioned. Otherwise, @JWardell is the final word on this in my book 

[Edit] Just skimmed through the entire manual. WOW, what an improvement from the real early manuals! But no mention of periodically charging to 90% or anything like that to balance the battery in the Owners Manual. In fact, no mention of anything really except to plug in when not in use.


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## garsh (Apr 4, 2016)

Ed Woodrick said:


> You NEED to charge past 95% to get the calculations to reset and like the battery management system equalize the batteries.





garsh said:


> This is incorrect. You only need to charge past 90%. Charging past 95% is not recommended.





Ed Woodrick said:


> Pretty sure that charging to 100% is in the book for when you take trips.


The topic was recalibrating the BMS, not taking a road trip.


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## GDN (Oct 30, 2017)

r-e-l said:


> how long is a long drive? I take it that dropping to 50% via many small drives doesn't count ....


That is correct. The many small drives are actualy what is causing it to calculate fewer estimated miles. I may have one of the best documented cases and it took several drives in the 100 to 200 mile range and then even a daily commute of 10 miles continued to help. https://teslaownersonline.com/threads/how-do-i-charge-next-to-regain-range.16703/post-290589

Sitting in the garage for a day or two at a time and it's only drives being 2 to 4 mile errands driven like a jack rabbit are what caused my calculated range to tank, however the battery definitely seems to be just fine.


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## MnLakeBum (Mar 17, 2021)

This is long but I’ll try to summarize my degradation problems that has my 2015 85D currently at the Tesla service center waiting for remanufactured battery at 112,856 miles. 

My full charge range when new in 2015 was about 268 but after a few months and 8,000 that was down to about 261. After that it was a very gradual loss to about 242 at 90k miles in the spring of 2019. A year ago at 103,000 miles the range had dropped to 226 miles and that was when the first signs of a problem with the HV battery showed up. I was driving it each Wednesday or Thursday 140 miles north to our cabin(all highway at mostly 75mph) and I would set it to charge to 90% with the departure timer so it wouldn’t sit at that 90% level for more than 20 minutes. I’ve never achieved better than about 82% of rated miles when driving 75mph on the highway so charging to 200 miles should allow me to go 160ish miles but less than that in freezing temperatures. 
On a return trip from the cabin last spring I started out with about 205 miles on the meter and 135 miles later started getting warning messages to charge at about 40 miles on the meter. 3.5 miles later I was stranded on the side of the highway with 32 miles left on the meter. I had the vehicle towed to the Tesla service center and they diagnosed and told me everything was normal with the battery. A couple weeks later I got the same message as I was rolling into are driveway at the cabin after the same 140 mile trip in slightly warmer, 50* temperatures. The battery meter was at 38 miles when the warning started. I took it back to the service center the following week(stopped at a supercharger on the way home as I didn’t want to risk another tow). They gave me the same story and recommended that I not drive the vehicle below a 15% charge level, lol. At this point I was super frustrated as I wrongly thought I had a range guarantee which they didn’t have on the Model S until 2020. The service center was not sympathetic to the fact that i couldn’t drive the vehicle below about 50 miles without fear of getting stranded. 
The problem of making the 140 mile weekly trip back and forth to our cabin went away once the weather warmed up as I could start with a full charge of about 220 miles and arrive with about 50 miles remaining on the battery meter. Once fall arrived we no longer went to the lake and I normally only drive about 50 miles a day so I no longer had any reason for range anxiety. By December of 2020 the max range had dropped under 200 miles but I guessed part of that could be the cold MN winters.

That reasoning was obviously faulty which I discovered last week when making a 85 mile round trip to visit my son at college. 80 miles into the trip with about 55 miles left on the battery meter, I lost all ability to accelerate or hold a high speed over 62 mph and by the time I reached home max speed was 55 mph. Luckily i made it home and was able to drive it normally after charging back up to 175 miles. Tuesday the day before i got it in for my appointment the service advisor called and said they would be replacing the battery. I’m not sure exactly why they changed their viewpoint but I was told swapping out batteries under warranty was much easier this year due to a change in policy. It will be interesting to see how the new one performs.


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