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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
Afaik its not a range bump anyway. The awd jsut got uprated and the performance downrated or more to say the 20 inch wheels got downrated. If you put 18 inch wheels on and change them in the menu it goes back up.
Two different things being discussed here:

What was being discussed:
The range increase from 310 to 325 for LR RWD. This was an energy increase (no change in the constant AFAIK from everyone I have asked, and also shows in EPA test results).

Not being referred to in this context:
The increase to 322 rated miles for 2020 (not a capacity increase, just a constant adjustment, in combination with better software which improved efficiency and also applied to older vehicles and thus provided more range in some circumstances).
 
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AAKEE

Member
Jan 8, 2021
193
180
Sweden
The range bump didn't apply to our 2018 LR-AWD models. 310 is it.
I’m new to Tesla but as I understand it all LR/P had 310 miles/499km as the range on the screen earlier? And that the constant was made to match this? So when calculating degradation from the 100% charge range you need to use 310/499 as the base?

Mine ’21 P had 499km also, until end of febuary/beginning of march when a update change the maximum range to 507km, which is coherent with the EPA range(315 miles/507km). I need to use that new factor 507km, otherwise the calculation is off. (IRL, I use SMT and see the battery calculated capacity that way.)
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
I’m new to Tesla but as I understand it all LR/P had 310 miles/499km as the range on the screen earlier? And that the constant was made to match this? So when calculating degradation from the 100% charge range you need to use 310/499 as the base?
Constant is different for 2018/2019 LR AWD (245Wh/rmi) and LR RWD (234Wh/rmi), and the constant has not changed for these vehicles, AFAIK.

The LR RWD had a few excess kWh unlocked (3.5kWh, better to think of as a 5% increase probably) and went from 310 rated miles to 325 rated miles, in early 2019. Of course this would not happen (there would still be a range increase though) if the particular car’s post-unlock capacity had degraded below 76kWh at the time of the update (and wouldn’t go above 310 rated miles if the post-unlock capacity was lower than 72.5kWh). However, there are (verified by TeslaFi range history plots?) reports that some vehicles did not see any range increase.

So for LR RWD it’s a bit confusing to determine which starting value you “should” use for calculations. I tend to use 76kWh, which is actually probably 77.8kWh. (This assertion is backed by EPA test results.) But no idea what starting capacity Tesla would use for warranty claims. Probably 72.5kWh if owner purchased with 310 rated miles!
 
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Dave EV

Active Member
Jun 23, 2009
1,700
1,157
San Diego
The LR RWD had a few excess kWh unlocked (3.5kWh, better to think of as a 5% increase probably) and went from 310 rated miles to 325 rated miles, in early 2019. Of course this would not happen (there would still be a range increase though) if the particular car’s post-unlock capacity had degraded below 76kWh at the time of the update (and wouldn’t go above 310 rated miles if the post-unlock capacity was lower than 72.5kWh). However, there are (verified by TeslaFi range history plots?) reports that some vehicles did not see any range increase.
Do you know if Tesla unlocked the capacity at the top or bottom of the SOC, or simply reduced the buffer at the bottom? In other words, did they raise or lower the max/min allowable voltage of the cells, or did they simply reduce the amount of hidden range below 0?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
Do you know if Tesla unlocked the capacity at the top or bottom of the SOC, or simply reduced the buffer at the bottom? In other words, did they raise or lower the max/min allowable voltage of the cells, or did they simply reduce the amount of hidden range below 0?
It was a cell voltage adjustment, but no idea whether top or bottom. I suspect it was bottom of the range. But evidence is very scarce (it would not be hard to determine with SMT readbacks or similar prior to the change). But it’s very likely it wasn’t actually a hidden usable buffer reassignment (see evidence below) - Tesla decides the minimum (and maximum) true SoC (cell voltage) allowed, and they just changed this value. Obviously they could have also changed the top end of the pack.


I don’t think it was a matter of just “unhiding” buffer that was already accessible but not visible, because the EPA test results showed less discharge energy in the initial LR RWD tests. So it simply was not available even if you drove until the vehicle stopped moving.

So to directly answer your question, they raised or lowered the cell voltage limits at the high/low ends.
 
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Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
It was a cell voltage adjustment, but no idea whether top or bottom. I suspect it was bottom of the range. But evidence is very scarce (it would not be hard to determine with SMT readbacks or similar prior to the change). But it’s very likely it wasn’t actually a hidden usable buffer reassignment (see evidence below) - Tesla decides the minimum (and maximum) true SoC (cell voltage) allowed, and they just changed this value. Obviously they could have also changed the top end of the pack.


I don’t think it was a matter of just “unhiding” buffer that was already accessible but not visible, because the EPA test results showed less discharge energy in the initial LR RWD tests. So it simply was not available even if you drove until the vehicle stopped moving.

So to directly answer your question, they raised or lowered the cell voltage limits at the high/low ends.

that is very strange. why did they never uncork the performance then? or the stealth performance? very odd. does that mean there is a bigger hidden buffer below the 4.5% buffer?
 

scottf200

Active Member
Feb 3, 2013
3,880
3,460
Chicagoland ModelX S603
Something that changed since this post is that there is a charging at a departure time built-in option. This means if your drive/usage is varying by the day of the week (workdays or work from home days or whatever) ... then your car will sit at the previous drives ending SOC % until the time the car calculates it needs to start charging to meet your 'departure time'.

This adds an *automatic* variance to the OCV readings which gives the BMS more variables for the calibration computations. So even if you pay a fixed rate for your kWh you can get benefit to using 'Scheduled Departure'. I'm in a TOU variable rate *but* the price/kWh is lowest until about 5am. That is when I set my departure time to every day. It usually ends around 4:30am.
1) No one liked the 'Scheduled Departure' idea for having more random times/durations for the OCV readings apparently.
Here is an example of someone I know and their charges that ended up below 50% over a couple of months (i.e. not consecutive days). All the rest started the SOC over 50%.
If they delayed their charging start times then they would have OCV readings 'randomly' over a couple of months.

v862i67.jpg

-_______________________________________________ _____________________________ ____________________________
2) Also as another option or combination of the two,
For any TeslaFI users you can also schedule whatever 'Charge Limit' setting changes you want. Add or remove any number of them it seems to start at any location (ie. at home and not vacation), any time, and any hour. I'm still thinking thru what I want to do.


8BtizTN.jpg
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
that is very strange. why did they never uncork the performance then? or the stealth performance? very odd. does that mean there is a bigger hidden buffer below the 4.5% buffer?
Nothing to uncork, and no.

If you look at the EPA data the energy available for the LR RWD was lower than that of the LR AWD, initially. The LR RWD of course had better range though (same nominal range rating of 310 miles but a better efficiency and a lower constant).

The unlock made them have identical available energy. Since they were using the same fundamental pack after all (with some minor differences later on but still the same energy in the pack).
 

Candleflame

Active Member
Mar 9, 2015
2,662
1,228
QLD, Australia
Nothing to uncork, and no.

If you look at the EPA data the energy available for the LR RWD was lower than that of the LR AWD, initially. The LR RWD of course had better range though (same nominal range rating of 310 miles but a better efficiency and a lower constant).

The unlock made them have identical available energy. Since they were using the same fundamental pack after all (with some minor differences later on but still the same energy in the pack).

but a stealth performance is just an awd, same battery and pre 2019 even same motor?
 

cybergates

Member
Feb 14, 2017
521
217
So Cal
in the family we have 2 x 2019 M3's (12/2018+ 6/2019) - both AWD - both started with 279(90%) and 310 max and now the 90% (252 for car 1, 249 for car 2) is and 100% (280 car 1, 277 car 2). Approx 10-11% battery life loss. car 1 is at 35K miles and does more commuter highway miles and car 2 is at 20K and is mostly city driving small trips. Hopefully this levels off?
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
@Candleflame and @AlanSubie4Life can you guys take it off to DMs since you are going off topic vs recovering 'Battery's Lost Capacity'
Sure. This started because the question came up about how much capacity had been lost on an LR RWD, in the context of someone wanting to recover their range using the strategies discussed here. Answering that always requires unpeeling this layer, sadly. Repeatedly. But yes, that specific discussion is more appropriate in the battery capacity loss thread, though I think it’s clear there’s a lot of overlap.

Anyway I have messaged @Candleflame to help resolve his outstanding questions...I think it’s pretty clear from above what Tesla did, and there’s now nothing additional to add to this discussion here by answering his remaining questions.
 
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Kashbunker

New Member
Mar 28, 2021
1
0
Tehachapi, CA
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.
Thank you for taking the time to post details . I bought my M3 on September 2018 as well. However, in November 2019 had to drive out and work in another city where I could not charge overnight . Overdose four months my battery went down from 308 -290 .
It has never recovered from that. I do not charge my battery every day and when I do I usually charge two around 80%
 

Gizmo35

Member
Aug 4, 2019
134
145
San Diego, CA
My car shows 230 miles at 90% and around 256 at 100%. Tesla said over the app that my battery is fine and that the car is underestimating my range. If i wanted to fix it, they suggest letting battery go down to 5% and the. Charge to 100%. Then going forward, I should let battery drain to 15-20% before charging back to 90% and it will fix itself over time. I haven’t tried that and just continue to charge from around 70% back to 90% daily.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
My car shows 230 miles at 90% and around 256 at 100%. Tesla said over the app that my battery is fine and that the car is underestimating my range. If i wanted to fix it, they suggest letting battery go down to 5% and the. Charge to 100%. Then going forward, I should let battery drain to 15-20% before charging back to 90% and it will fix itself over time. I haven’t tried that and just continue to charge from around 70% back to 90% daily.
Wow, that's a really big outlier. How many miles on your car?

I guess you don't take road trips? That's the natural time to do this sort of cycling without any inconvenience (though it doesn't allow for sleeping which is alleged to be important...). You'd be an excellent candidate to try the strategies in this thread, I suppose.

I have my doubts about how much it will recover, but Tesla could definitely be right if you haven't gone under 70% for a long time.

Right now this is around 20% capacity loss which is definitely one of the worst reports. But it would be interesting to see how real it actually is. And as Tesla says, the only way to really know is to take it to low SoC (maybe let it sleep for a few hours as suggested here) and then charge it up again.
 
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Gizmo35

Member
Aug 4, 2019
134
145
San Diego, CA
Wow, that's a really big outlier. How many miles on your car?

I guess you don't take road trips? That's the natural time to do this sort of cycling without any inconvenience (though it doesn't allow for sleeping which is alleged to be important...). You'd be an excellent candidate to try the strategies in this thread, I suppose.

I have my doubts about how much it will recover, but Tesla could definitely be right if you haven't gone under 70% for a long time.

Right now this is around 20% capacity loss which is definitely one of the worst reports. But it would be interesting to see how real it actually is. And as Tesla says, the only way to really know is to take it to low SoC (maybe let it sleep for a few hours as suggested here) and then charge it up
Wow, that's a really big outlier. How many miles on your car?

I guess you don't take road trips? That's the natural time to do this sort of cycling without any inconvenience (though it doesn't allow for sleeping which is alleged to be important...). You'd be an excellent candidate to try the strategies in this thread, I suppose.

I have my doubts about how much it will recover, but Tesla could definitely be right if you haven't gone under 70% for a long time.

Right now this is around 20% capacity loss which is definitely one of the worst reports. But it would be interesting to see how real it actually is. And as Tesla says, the only way to really know is to take it to low SoC (maybe let it sleep for a few hours as suggested here) and then charge it up again.
My car has 27,400 miles. I do go on road trips. As a matter of fact I came back from one yesteday. Arrived home with 14% and charged to 90% overnight. Range estimate still 230. My daily commute is around 36 miles round trip. My lifetime efficiency is 267 wh/mile.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,425
11,326
San Diego
My car has 27,400 miles. I do go on road trips. As a matter of fact I came back from one yesteday. Arrived home with 14% and charged to 90% overnight. Range estimate still 230. My daily commute is around 36 miles round trip. My lifetime efficiency is 267 wh/mile.

Given that info, I don’t think that range is coming back to any appreciable degree no matter what Tesla says (I feel like the cycling is no guarantee anyway - it only solves the problem if that is the problem). One of the worst I have seen. I guess you could try running it down to 0% in a safe & controlled place (can use the heat in your garage unless it forces it to shut it off - no idea), but probably not worth it. Let us know if it does come roaring back though. At this rate you might make warranty replacement though; 2/3 of the way there. Depends on how much it slows down. It would actually have to slow down a lot (which it might!).
 

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