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How I Recovered Half of my Battery's Lost Capacity

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
Research by battery scientists and referenced at Battery University, for example, quantifies this and is obviously well known and acknowledged. What you say could be true, depending on how you define "significant". I am not trying to change your behavior, nor am I judging it. It is a choice. Accurate information will help new owners make their own choices.
It’s really a question of contributors. There’s not a lot of debate that the mechanisms you describe likely behave that same way in Tesla batteries. So if you want to optimize they are good guidelines to follow. (It’s likely that high SoC matters - I have 40% capacity loss on an EV battery (GM) that is always kept at 100% - when I have it replaced I will try to find an EVSE that allows me to set a charge limit. But even this is just correlation - not causation. Many of those vehicles are kept at 100% and this is probably a bit worse than most, for example.)

However, the available evidence suggests that other factors by far dominate the capacity loss people see for Teslas. Those factors appear to be:

1) Battery pack lot/date of manufacture
2) Random chance.
3) Use (cycles).
4) Perhaps hot climates/storage.

So you can do everything perfectly and still end up on the low end of the distribution.

We actually just don’t know what dominates. From this thread and tons of anecdotal evidence, it seems to me to be mostly luck. Only Tesla has all the data that would clearly show what are the most important factors though.
 
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Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
Everyone's definition of "significant" is different, but it seems intuitive that charging to the more extreme range of voltages and SOC percentages is not as healthy for a battery than staying in the less extreme middle ranges. While it's unlikely to matter all that much, it does seem that many people are more sensitive to small range changes than expected; otherwise, why would there be so many comments on these threads?

When people pay for more range, and then within a couple years seem to lose that range, where now their model's range is less than that of a smaller-batteried model, it's understandable that some people get upset. Of course, if they had bought the smaller-batteried model, that would now have even less range, but appealing to logic doesn't always help.

Model 3 pricing is primarily differentiated by battery size, so people are sensitive to when their battery seems to lose range, almost instantly when they take their 3 home.

yes i am very sensitivie when i buy a car with an advertised EPA range and after less than a year it has 7% degradation already. its close to being false advertising.
 

Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
It’s really a question of contributors. There’s not a lot of debate that the mechanisms you describe likely behave that same way in Tesla batteries. So if you want to optimize they are good guidelines to follow. (It’s likely that high SoC matters - I have 40% capacity loss on an EV battery (GM) that is always kept at 100% - when I have it replaced I will try to find an EVSE that allows me to set a charge limit. But even this is just correlation - not causation. Many of those vehicles are kept at 100% and this is probably a bit worse than most, for example.)

However, the available evidence suggests that other factors by far dominate the capacity loss people see for Teslas. Those factors appear to be:

1) Battery pack lot/date of manufacture
2) Random chance.
3) Use (cycles).
4) Perhaps hot climates/storage.

So you can do everything perfectly and still end up on the low end of the distribution.

We actually just don’t know what dominates. From this thread and tons of anecdotal evidence, it seems to me to be mostly luck. Only Tesla has all the data that would clearly show what are the most important factors though.

living in the tropics i would be convinced too that hot climate causes (my) degradation. However, on teslafi you can now sort fleet ranges according to temperature. and there isnt really much difference. Maybe 1% if that. so im sure we can discount that.
 

dhrivnak

Active Member
Jan 8, 2011
4,417
3,577
NE Tennessee
Research by battery scientists and referenced at Battery University, for example, quantifies this and is obviously well known and acknowledged. What you say could be true, depending on how you define "significant". I am not trying to change your behavior, nor am I judging it. It is a choice. Accurate information will help new owners make their own choices.
The wild card is that 0 is not 0 nor is 100% completely full either with Tesla. There are buffers at both the top and bottom which unfortunately they do not disclose. So it is very likely that 80% on the Tesla screen is in reality 75%.
 
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Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
Research by battery scientists and referenced at Battery University, for example, quantifies this and is obviously well known and acknowledged. What you say could be true, depending on how you define "significant". I am not trying to change your behavior, nor am I judging it. It is a choice. Accurate information will help new owners make their own choices.

yes but this has never really been shown to translate it any meaningful way to teslas vehicles.
 
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Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
The wild card is that 0 is not 0 nor is 100% completely full either with Tesla. There are buffers at both the top and bottom which unfortunately they do not disclose. So it is very likely that 80% on the Tesla screen is in reality 75%.

there is no top buffer on teslas anymore. only the Roadster had a top buffer as it only charged to 4.15V at 100% (so like 93% true SOC). S/X/3 all charge to 4.2V which has been arbitarily decided as being 100%.

Tesla Model 3 has 4.5% bottom buffer and then maybe 1kwh brick protection but by the time it gets to -4.5% the voltage is already pretty low and with proper load undervolting the cells could happen...

Some Model S have no bottom buffer. 0 means 0.
 
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MY-Y

Member
Mar 4, 2020
883
917
MD
there is no top buffer on teslas anymore. only the Roadster had a top buffer as it only charged to 4.15V at 100% (so like 93% true SOC). S/X/3 all charge to 4.2V which has been arbitarily decided as being 100%.

Tesla Model 3 has 4.5% bottom buffer and then maybe 1kwh brick protection but by the time it gets to -4.5% the voltage is already pretty low and with proper load undervolting the cells could happen...

Some Model S have no bottom buffer. 0 means 0.
My 2020 MY charges to 4.188 volts at 100%, so maybe there is a bit of buffer at the top.
Screenshot_20210421-112245.jpg
 
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MY-Y

Member
Mar 4, 2020
883
917
MD
Charging stops based on the maximum cell voltage, not the average. Which looks to be 4.194 in your screenshot.
I just looked at the three screenshots that show the voltage of all 96 cells when I charged to 100%; 4.194 was the max in the pack. I'm not sure how close this equates to a true 100%.
 

Nglewis92

New Member
Jan 5, 2019
4
5
Murfreesboro, TN
Is this range loss normal-ish? Feels like 12% in 2.5 years is trending towards a warranty claim since the battery is degrading faster than 3.75%/year, but I also understand it flattens out over time. That said, these teslafi stats vs. other comparable vehicles at the same odometer reading are concerning. Thoughts?
 

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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
Is this range loss normal-ish? Feels like 12% in 2.5 years is trending towards a warranty claim since the battery is degrading faster than 3.75%/year, but I also understand it flattens out over time. That said, these teslafi stats vs. other comparable vehicles at the same odometer reading are concerning. Thoughts?

Yep, it's normal. Someone has to be on the low end of the distribution, after all. It's you, in this case! You're really quite close to other owners - just 4-5% worse than half of them.

As you said, expect it to level out, perhaps even recover slightly as it has done recently (can follow some of the methods suggested in this thread to see what happens), and enjoy the vehicle. Budgeting ~10% capacity loss (at least - I budget and expect 15-20%) when buying an EV is something all owners should do when making their purchasing decision, at least if they plan to hang on to the car for more than a couple years.

Teslas are actually doing relatively well in this regard (as mentioned, my Chevy Spark EV has lost ~40% capacity over 4.5 years). But it's normal and expected to lose quite a bit of capacity from a battery due to time and use and there's not a lot you can do about it.

I hope things level out for you - I know mine has slowed way down over the last year.
 

Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
Is this range loss normal-ish? Feels like 12% in 2.5 years is trending towards a warranty claim since the battery is degrading faster than 3.75%/year, but I also understand it flattens out over time. That said, these teslafi stats vs. other comparable vehicles at the same odometer reading are concerning. Thoughts?
Unfortunately the model 3 batteries degrade much faster than the model s batteries... 12% in 2.5 years is just slightly worse than normal. Most model 3s after 2 years are around 10%. However looking at the high milage leaderboard degradation seems to stop at around 12 to 13%, even for cars with 300k km on the clock.
 

Nglewis92

New Member
Jan 5, 2019
4
5
Murfreesboro, TN
Yep, it's normal. Someone has to be on the low end of the distribution, after all. It's you, in this case! You're really quite close to other owners - just 4-5% worse than half of them.

As you said, expect it to level out, perhaps even recover slightly as it has done recently (can follow some of the methods suggested in this thread to see what happens), and enjoy the vehicle. Budgeting ~10% capacity loss (at least - I budget and expect 15-20%) when buying an EV is something all owners should do when making their purchasing decision, at least if they plan to hang on to the car for more than a couple years.

Teslas are actually doing relatively well in this regard (as mentioned, my Chevy Spark EV has lost ~40% capacity over 4.5 years). But it's normal and expected to lose quite a bit of capacity from a battery due to time and use and there's not a lot you can do about it.

I hope things level out for you - I know mine has slowed way down over the last year.
Thanks!
 

DAJ8895

Member
Mar 18, 2021
15
14
Northern Virginia
Like many others, I have been concerned with loss of 100% indicated battery range on one of my Model 3s. My P3D (build date 9/13/2018, delivery date 10/8/2018) had gotten down to 270.3 miles at 100% charge on January 20, 2020, at about 30,700 miles, which is a loss of 40.8 miles since the car was new.

I posted about going to the service center to talk with them about battery degradation, which I did on March 9, 2020. It was a great service appointment and the techs at the Houston Westchase service center paid attention to my concerns and promised to follow up with a call from the lead virtual tech team technician. I detailed this service visit in the following post:

Reduced Range - Tesla Issued a Service Bulletin for possible fix

While that service visit was great, the real meat of addressing the problem came when I spoke to the virtual tech team lead. He told me some great things about the Model 3 battery and BMS. With the knowledge of what he told me, I formulated a plan to address it myself.

So here is the deal on the Model 3 battery and why many of us might be seeing this capacity degradation.

The BMS system is not only responsible for charging and monitoring of the battery, but computing the estimated range. The way it does this is to correlate the battery's terminal voltage (and the terminal voltage of each group of parallel cells) to the capacity. The BMS tries to constantly refine and calibrate that relationship between terminal voltage and capacity to display the remaining miles.

For the BMS to execute a calibration computation, it needs data. The primary data it needs to to this is what is called the Open Circuit Voltage (OCV) of the battery and each parallel group of cells. The BMS takes these OCV readings whenever it can, and when it has enough of them, it runs a calibration computation. This lets the BMS now estimate capacity vs the battery voltage. If the BMS goes for a long time without running calibration computations, then the BMS's estimate of the battery's capacity can drift away from the battery's actual capacity. The BMS is conservative in its estimates so that people will not run out of battery before the indicator reads 0 miles, so the drift is almost always in the direction of estimated capacity < actual capacity.

So, when does the BMS take OCV readings? To take a set of OCV readings, the main HV contactor must be open, and the voltages inside the pack for every group of parallel cells must stabilize. How long does that take? Well, interestingly enough, the Model 3 takes a lot longer for the voltages to stabilize than the Model S or X. The reason is because of the battery construction. All Tesla batteries have a resistor in parallel with every parallel group of cells. The purpose of these resistors is for pack balancing. When charging to 100%, these resistors allow the low cells in the parallel group to charge more than the high cells in the group, bringing all the cells closer together in terms of their state of charge. However, the drawback to these resistors is that they are the primary cause of vampire drain.

Because Tesla wanted the Model 3 battery to be the most efficient it could be, Tesla decided to decrease the vampire drain as much as possible. One step they took to accomplish this was to increase the value of all of these resistors so that the vampire drain is minimized. The resistors in the Model 3 packs are apparently around 10x the value of the ones in the Model S/X packs. So what does this do to the BMS? Well, it makes the BMS wait a lot longer to take OCV readings, because the voltages take 10x longer to stabilize. Apparently, the voltages can stabilize enough to take OCV readings in the S/X packs within 15-20 minutes, but the Model 3 can take 3+ hours.

This means that the S/X BMS can run the calibration computations a lot easier and lot more often than the Model 3. 15-20 minutes with the contactor open is enough to get a set of OCV readings. This can happen while you're out shopping or at work, allowing the BMS to get OCV readings while the battery is at various states of charge, both high and low. This is great data for the BMS, and lets it run a good calibration fairly often.

On the Model 3, this doesn't happen. With frequent small trips, no OCV readings ever get taken because the voltage doesn't stabilize before you drive the car again. Also, many of us continuously run Sentry mode whenever we're not at home, and Sentry mode keeps the contactor engaged, thus no OCV readings can be taken no matter how long you wait. For many Model 3's, the only time OCV readings get taken is at home after a battery charge is completed, as that is the only time the car gets to open the contactor and sleep. Finally, 3 hours later, OCV readings get taken.

But that means that the OCV readings are ALWAYS at your battery charge level. If you always charge to 80%, then the only data the BMS is repeatedly collecting is 80% OCV readings. This isn't enough data to make the calibration computation accurate. So even though the readings are getting taken, and the calibration computation is being periodically run, the accuracy of the BMS never improves, and the estimated capacity vs. actual capacity continues to drift apart.

So, knowing all of this, here's what I did:

1. I made it a habit to make sure that the BMS got to take OCV readings whenever possible. I turned off Sentry mode at work so that OCV readings could be taken there. I made sure that TeslaFi was set to allow the car to sleep, because if it isn't asleep, OCV readings can't get taken.

2. I quit charging every day. Round-trip to work and back for me is about 20% of the battery's capacity, and I used to normally charge to 90%. I changed my standard charge to 80%, and then I began charging the car at night only every 3 days. So day 1 gets OCV readings at 80% (after the charge is complete), day 2 at about 60% (after 1 work trip), and day 3 at about 40% (2 work trips). I arrive back home from work with about 20% charge on that last day, and if the next day isn't Saturday, then I charge. If the next day is Saturday (I normally don't go anywhere far on Saturday), then I delay the charge for a 4th day, allowing the BMS to get OCV readings at 20%. So now my BMS is getting data from various states of charge throughout the range of the battery.

3. I periodically (once a month or so) charge to 95%, then let the car sleep for 6 hours, getting OCV readings at 95%. Don't do this at 100%, as it's not good for the battery to sit with 100% charge.

4. If I'm going to take a long drive i.e. road trip, then I charge to 100% to balance the battery, then drive. I also try to time it so that I get back home with around 10% charge, and if I can do that, then I don't charge at that time. Instead, let the car sleep 6 hours so it gets OCV readings at 10%.

These steps allowed the BMS to get many OCV readings that span the entire state of charge of the battery. This gets it good data to run an accurate calibration computation.

So what's the results?

20200827Battery100PctRange.png


On 1/20/2020 at 30,700 miles, I was down to 270 miles full range, which is 40.8 miles lost (15.1 %). The first good, accurate recalibration occurred 4/16/2020 at 35,600 miles and brought the full range up to 286 miles. Then another one occurred on 8/23/2020 at 41,400 miles and brought the range up to 290 miles, now only a 20 mile loss (6.9 %).

Note that to get just two accurate calibration computations by the BMS took 7 months and 11,000 miles.

So, to summarize:

1. This issue is primarily an indication/estimation problem, not real battery capacity loss.
2. Constant Sentry mode use contributes to this problem, because the car never sleeps, so no OCV readings get taken.
3. Long voltage stabilization times in the Model 3 prevent OCV readings from getting taken frequently, contributing to BMS estimation drift.
4. Constantly charging every day means that those OCV readings that do get taken are always at the same charge level, which makes the BMS calibration inaccurate.
5. Multiple accurate calibration cycles may need to happen before the BMS accuracy improves.
6. It takes a long time (a lot of OCV readings) to cause the BMS to run a calibration computation, and therefore the procedure can take months.

I would love if someone else can perform this procedure and confirm that it works for you, especially if your Model 3 is one that has a lot of apparent degradation. It will take months, but I think we can prove that this procedure will work.
Awesome info, I have a 2020 Model Y, I am certainly going to change my charging habits to see if it works for me, because I have already see a loss of range with less than a year of ownership.
 

jrcheesecake

New Member
May 14, 2021
1
3
Toronto
Hi there,
I don't know how this approach works/worked for others. But it seems to work very well for me so far, at least from looking at what it appears.
I would like to thank the OP and everyone on the post for the valuable info :)

Fact: model 3. 2018, LR, RWD, location: Canada (warning: you will see data in KM not miles)

Background:
1. Previously had followed Tesla's "advice" to keep vehicle plugged in whenever possible.
2. Have access to a L2 charging facility at work place, but only charge 4 hours whenever possible. Meaning I don't set a specific % to charge to.
3. Not charging at home most of time but do keep the M3 plugged in.
4. 100% full indicated KMs have been slowing going down to around 458 (or 286miles) at some point
5. Found this post back in February.
6. Started to try this method in Mid-March.

What I did:
1. Keep M3 Un-plugged whenever possible.
2. Charge twice at work whenever KM reading is below 200 (usually Tues/Friday).
3. Always set charge amount to 90%. (I did charge to 100% once just to test)

Other factors:
1. Temperature does warm up during the test period. So this can be a factor. However, the KM indicator was recovering even when the temperature was still low. It was below 0 c back in March/early April.
2. It may be early to say the battery capacity is really recovered at this moment. All we see could be just nominal.
3. Will keep monitoring.

Result:
Sharing a graph from Excel that I have been tracking by myself. Sorry that I don't use any third party software such as TeslaFi.
 

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texasdoc

Member
Jun 1, 2019
9
9
Austin, TX
Does a Model 3 with an inaccurate range calculation suffer from an actual loss of range? I.e., if my car really has enough battery capacity to drive 290 miles, but the BMS says 270 at 100% SOC, will the car drive 270 or 290 miles, all other things being equal?
 

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