How I Recovered Half of my Battery's Lost Capacity

[TLCTimFL]

Thank you for the write - up!
This approach is exactly what my local service center has recommended to repair my SR+. It has been down to 214 at full charge but I too was treating my car the same as you. (12,000 miles though).

My midrange M3 started at 264 miles the first few full charges 1 1/2 yrs ago. With around 19,000 miles, I seldom charge above 90% (220 mi) when using my home Tesla charger. I recharge a couple times a week. Very seldom do I use a Supercharger unless I'm traveling outside the range. When I do charge to 100%, I get into the 240s. So I'd assume I'm not having the same issues and I run Sentry ALL the time because my car sits outside 24/7.

How would I assure the car "sleeps" for hours at a time other than shutting off Sentry and the 105 degree protection? It would be interesting to see if I could recover some of those "lost" miles.

 

[M109Rider]

Thanks to the OP for the great post.
I just got back from a 12,000km / 7,456 mile road trip.
I’m now at 107,220 km’s or 66,623 miles.
I had sentry mode on 24/7, but had many days where I drove over 3 hours straight.
I’m sitting at 5.4% loss after my return. I was around 6% when I left.
Maybe the car did some calibrating when I was away.
Again, thanks for the post.

 

[ediflyer]

Re vampire drain - I thought the 3 was generally worse than the S/X in that regard, not better? (lots of articles but example at Tesla Model 3 "Phantom Drain" compared to Model S and Model X). Tesla also generally seem to be much worse than other manufacturers in that regard. I almost never use Sentry Mode as the vampire drain with it is brutal compared to when it isn't enabled.

I don't have home charging so I already leave the car at various SOCs for hours and days at a time and I'm still seeing a slow, continuous reduction in TeslaFi - maybe it would be more marked if I left it plugged in, I don't know. I hope it levels out going forward...

 

[Big_G]

Superb post, so pleased i found it. My SR+ has covered 7700 mile in 9 months and the range has dropped from 234 to 212, nobody could explain why ... Tesla said it must have been a software update that has caused some cells to misreport their capacity, yet every time there's a software update my range drops again. My journeys are are all very short and i charge to 80% every night. Trying the theory out on this one.

 

[KetchupKilla]

Can't say I'm super impressed with the battery. I'm at 12000 miles now and down 20 miles. I was told 5% loss is normal withing the first 12000 and then about 1% every 12000 miles but I'm constantly seeing the battery losing capacity.

 

[Battpower]

Tesla also generally seem to be much worse than other manufacturers in that regard.

I can confirm that from my experience. I think it comes down to Tesla choice of cell chemistry and approach to relatively tight battery management. My S spends far more (in my case wasted) effort balancing, heating, cooling, reducing regen etc than my little Renault EV that pushes the battery far less but doesn't need to fuss with it either.

But the Renault is only an adequate means of transport.

 

[spectrum1337]

.....
Or, say you want to flip on the windshield wipers to wash off a bug flattened right in your line of vision. If you’re like me, you’ll have to pull over to the side of the road and browse through the logical decision tree on the touch screen (that saves a lot of weight, I’m sure) before you can home in, minutes later, on the part of the algorithm that gives you several choices for windshield wiper activation.
...

FYI the wiper control is on the left stalk, just press it in . You don't need to take your eyes off the road.

 

[Battpower]

The range display is our only readily available window into the supposed health of the batteries.

This idea really is for ostriches. Head in the sand and all's well. If you are that uninterested in your battery health then not much point reading information posted here.

My commute, which used to take my car from 90% to 76-75%, now takes my car from 90% to 68-67%, despite maintaining roughly same wh/mi average.

Ah, you must be driving faster, on flat tires, have the a/c on higher with colder outdoor temps. Or your battery could be loosing capacity / useable capacity through multiple processes.

 

[erb2000]

However the car thinks the range has been lost. I'm unlikely to drive my car to 0 to find out if its hiding range so I drive within the 20-90% of the battery displayed range. I recently went on a 800 mile drive with a 250 mile stretch with no tesla charging. My displayed range is 272 miles and my car's nav plotted the route as if I could make it with 10% left at my destination. Well, I could not..even driving at the rated wh/mi, I was gonna be stuck so luckily I had the foresight to buy the expensive Chademo adapter and plug in at a 3rd party charger on the way to add another 20% or so. Point is, on long drives, its good to know what the cars estimated range in miles is because outside major interstates, tesla charging can be vastly spread out and the nav estimations are far to optimistic.

I keep an eye on the estimated percent SOC at the destination (next charger). If it drops below 8% then I slow down.

 

[Battpower]

Correction:

Somehow a quote got lost when I posted. I had intended:

Another observation which many people have been saying for a long time - change the display to show % instead of miles and stop worrying about it!

This idea really is for ostriches. Head in the sand and all's well. If you are that uninterested in your battery health then not much point reading information posted here.

 

[Rasputin]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

I own a Model 3 and drive it only infrequently ... especially now during the Covid-19 crimp on places to go. Now I'm sure all you young'uns out there will puzzle over how I could possibly lose some sharpness in my senior years; after all, you (and I, too, when I was a young'un) are bright, quick on your feet, sharp memory, and all the rest of the admirable characteristics of not-old humans, AND YOU'LL NEVER GIVE IN TO THE RAVAGES OF AGE, EITHER. Am I not right?

The Tesla autos have sometimes been called, with pride, "a computer on wheels." However, when I describe my M3 that way to others, it's with an inward groan. Why? It is so difficult to do anything, even simple things like open the glove box. In all the ICE cars I've ever driven, it's been easy. A/C? Sure, just reach over WITHOUT HAVING TO TAKE MY EYES OFF THE ROAD and make the adjustments by touch. No way to do that in my computer on wheels.

(btw, I fully expect there will be many crash descriptions of seniors taking their eyes off the road too long and crashing into some innocent car, guard rail at the edge of a cliff, or oncoming fully loaded semi.)

Or, say you want to flip on the windshield wipers to wash off a bug flattened right in your line of vision. If you’re like me, you’ll have to pull over to the side of the road and browse through the logical decision tree on the touch screen (that saves a lot of weight, I’m sure) before you can home in, minutes later, on the part of the algorithm that gives you several choices for windshield wiper activation.

This retired aerospace engineer, who helped design the control system of the GPS satellite decades ago, longs for the simplicity of an old ICE car! Same for my wife, who refuses to drive the M3 because it is “Too complicated.”

Elon! Here’s a demographic that you might not reach until you design a simple ecar: The really senior cohort that really doesn’t need 0 – 60 in 3 seconds. (I tried to think of a name for a senior-appropriate Tesla that could be added to the S3XY lineup, but I nodded off. Maybe after my nap.)

OK, I too am a senior, cruising along in my ninth decade, and I love my M3. You don’t have to do things the way you describe. Want to open the glove box, use voice command and say “Open the glove box.” BINGO! Want a quick window clean, press the button on the end of the steering wheel stalk. VOILA! Want to turn on and/or adjust windshield wiper speed or increase/decrease car temperature or fan speed, or turn on the rear camera, voice command will do it. Does a bunch of other stuff as well. My M3, along with everyone else’s, has become increasingly easy and far less complicated to drive. At first, it’s a bit intimidating because it’s so different from an ICE vehicle, but it’s a very quick learning curve, and I think it’s a great car for seniors—if they install the updates and take advantage of what they provide. Don’t understand why you don’t know this, but I still enjoyed your post. Hope you read this after your nap.

 

[Harry1]

Lot's of decent information here, but I'm pretty sure that it is not all quite correct.
...
I still highly disagree with the sitting at 100% is bad, it's bad ONLY if you leave if there for a long time, like months, or years.
...
As an Electrical Engineer, 100% battery charge can only be measured when the battery has been accepting effectively no charge and then let the battery temperature settle down and then measure the OCV.

BUT, the biggest thing is that you don't gain any battery charge. Nothing in this makes the battery 30%, 50% better. It is ONLY setting the guess-o-meter values. . . .

As an Electrical Engineer, I would think you would better appreciate the value of calibrated instruments.

Sure, the readings are not perfect, but the Tesla Guess-O-Meter is WAY better than my old Chevy Volt's meter, mainly because Tesla knows the route you're taking and elevations along that route.

Another thing I would like you to clarify for me ...

You are the 1st person I've seen to state that leaving your battery charged to 100% for days or weeks up to a month is not harmful. (!)

On what do you base that claim?

 

[Battpower]

On what do you base that claim?

Hanging out in the wrong threads?!

 

[M109Rider]

Hanging out in the wrong threads?!

In a few threads up, you suggested that setting visuals to %, means you have your head in the sand when it comes to battery health.

I set my visual to %, and not KM’s/Miles, because I took the time to understand how the battery works, what is good for it, what is bad for it, and I know that when it shows a given (__)% (SOC) loss, that doesn’t necessarily mean it has that actual loss..

Suggesting that folks heads are in the sand if they chose %, suggests your understanding of why they chose it, and perhaps how much you know about the BMS is presumptuous, and weak.

 

[djrodtc]

Your experiences matches mine, I lost about 10% on my AWD range with only 18000km and 10 months of life, to get something baxk I tried:

Setting max charge from 80 to 90
Discharge the car to 10% supercharge to 100 all in one drive

This give me about 5-8km back, so nothing worth it.

Then somebody pointed to me that my car only had 18000 but since I used sentry about 10h/ day at work that my battery had a bigger use and tear so I did this:

- I let the car discharge down to 10% in several days at about 20% discharge per day and then charge it back to 90% at home, no supercharging, and leave it at that for several hours
- Stop using sentry at work

Then I gained almost 20 km back up and it’s been like that since.

I started my experiment with 448km Max range and I’m now at 468, still far from my 499 when new but I started today another slow discharge of 20% per day and see what happens

 

[AlanSubie4Life]

Thanks for the interesting and thoughtful post! It is substantial food for thought.

. However, the drawback to these resistors is that they are the primary cause of vampire drain.

I kind of doubt this. What is the value of the bleed resistor? Once we know that we can calculate, though...

I guess it is possible that vampire drain (*after rebalancing is complete*) is actually very low on Model 3, but it certainly is hard to determine. My best estimate is around 40W average in an optimized state, but that is derived after a brief period of sitting, and perhaps after longer periods of sitting the average is lower (again, difficult experiment to perform repeatably).

The other comment I would have here is that once the balancing is complete, they don’t bleed anymore regardless of the resistor value, do they? Once the battery is balanced (all bricks at same voltage), there isn’t a need to bleed. So I could see a smaller resistor value leading to greater short term vampire loss (quicker rebalancing), but as far as longer term vampire loss is concerned I can’t see the resistor value as mattering.

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 %).

Originally you had 78-79kWh.

This is actually 290*245 = 71kWh

And

270*245 = 66.1kWh

So you recovered from ~15% loss to ~9% loss.

This is still substantial recovery, of course.

1. This issue is primarily an indication/estimation problem, not real battery capacity loss.

How would you explain calibrated charging interval experiments showing shorter charge intervals on cars showing loss of capacity? In general, you can estimate charge times within a few minutes. This indicates that the estimates of capacity are close to accurate.

Every time we have really dug into it with calibrated charging experiments here (we know what the charging overhead is from the EPA documents and also from other methods), the car’s estimate of energy available appears to be within 1-2% of accurate.


Still, interesting. I’ll try leaving my car sitting at a low charge for a few hours a couple times over the next week. I really need to measure the discharge energy on the car meter as well from a high SoC - haven’t done that in a while, and now that capacity is degraded it should show a lower value for how much was used for a full discharge. (As we well know, the discharge energy does not capture all the energy used (off by perhaps 1%) - I can’t compare that value to the charge event or the BMS estimate. I’m just talking about comparing relative to my prior discharge events.)

To me it seems that charging event energy and discharging event energies both point towards the BMS rated miles estimate as being an accurate assessment of energy available.

But, if that is true, I am curious about exactly what happened within your battery that made more energy available over time! 15-20 rated miles is quite significant!

Are you sure the 270 at 100% was not measured at a time when the battery had insufficient time to balance? I could see doing a charge to 100% and then immediately driving. This would lead potentially to a result where your 100% was limited by the voltage cap on your weakest brick (since it would max out soonest). If the battery had been left at that state, of course it would have bled down that brick and then started charging all bricks in series some more - which would have resulted in more energy available than 270 rated miles.

To me that’s the first idea that comes to mind for how available energy would go UP in a battery over time. I assume it is not self-healing! And we know capacity loss in general is real, as the battery has various deleterious physical mechanisms by which it can hold less energy over time.

So what was the exact situation on the charge to 100% (you said the 270 was not an extrapolation, I think - obviously we ignore any extrapolation data points for this discussion)? Did it sit overnight or for 10-24 hours? Or did you charge and then go?

 

[Battpower]

I set my visual to %, and not KM’s/Miles, because I took the time to understand how the battery works, what is good for it, what is bad for it, and I know that when it shows a given (__)% (SOC) loss, that doesn’t necessarily mean it has that actual loss..

Suggesting that folks heads are in the sand if they chose %, suggests your understanding of why they chose it

You are correct that I was / am making such an assumption, and it is based on most of such advice has been followed by "..... and then just don't worry about it."

Of course, if you get what's going on and are watching for changes in percentage after consistent journeys etc, then you are clearly making the call based on understanding. The 'head in the sand' comment was based on very different situations and in the absence of clear, concise and accurate posts such as the op of this thread.

I think it is important to keep in mind that there are two very different issues. One is if a vehicle is accurately reporting its maximum range, and the other is how an owner would see real loss of capacity in the battery.

 

[TEG]

Below is a snippet of the text conversation I had with a service advisor at my local service center. It aligns with what you were told. This text exchange was for my SR+, but I’ve been following the advice given in the text exchange below, and my new-to-me car has actually gained range since I took ownership.

That is painful for long distance road trips where you just make it to a supercharger on low battery SoC and immediately start high speed charging.
Some people even suggested to stretch out stops to more distant superchargers to arrive with lower SoC so that you get the higher current charging that comes with lower battery charge states. (Car supercharges more rapidly at 20% SoC than at 60% SoC for instance.)
This is part of some tradeoffs of convenience (less time waiting at Superchargers) vs battery care for longevity.
Given the option to stop more times and accept slower charging from higher SoCs, I would tend to pick that to be nicer to my battery instead of letting it drain down to a low battery charge state.

 

[TEG]

...
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.
...

So, to me, that is another trade-off. It sounds like you could be slowly degrading your battery more so that you can get better capacity readings from the BMS.
I tend to try to keep my battery in the 40%-80% range nearly all the time and only go above or below for a rare long distance road trip.

Personally, if I felt my range indicator was to drift too far from (what I think is) battery reality, I would do a one time skip on charging, and one time charge to 90% just to get more readings, but I wouldn't make it a habit of letting it get down to 20% on a regular basis.

 

[AlanSubie4Life]

This is part of some tradeoffs of convenience (less time waiting at Superchargers) vs battery care for longevity.
Given the option to stop more times and accept slower charging from higher SoCs, I would tend to pick that to be nicer to my battery instead of letting it drain down to a low battery charge state.

This is way off topic...so will be my last comment on this...but:
I don’t know that there is any evidence that charging at 250kW at 10% SoC is any more stressful than charging at ~170kW at 40% SoC. For all we know 250kW at 10% SoC may be less stressful. All depends on how fast those ions can diffuse I think?

So I’m not sure that following a non-optimal charging strategy on a road trip to attempt to preserve the battery is actually helpful for preserving the battery.

A better strategy for battery preservation (which undoubtedly IS less stressful) might be to avoid V3 Superchargers I suppose. But the V3 have the distinct advantages of being much faster, and also actually working, for now (many V2 Superchargers are broken in my experience - providing ~118kW rather than 150kW, for example - about 50% of the time I have to move stalls to get a higher rate). You could additionally search out partially broken V2 superchargers to further preserve your battery (it’s usually not hard to find one that will charge at 30-72kW, if you try them all). The overhead in searching them out doesn’t matter since time is obviously not a factor. Of course, going immediately to a shared charger with another vehicle is another winning strategy here (probably would annoy the other driver though).

I would have had a harder time driving from San Diego to Portland in a day without V3 Superchargers. Possible still (assuming the V2 were working properly), but the V3 sure are nice. 1076 miles at an average speed of 58mph! (~18.5 hours). 4:10AM to 10:40PM