The usual Battery Degradation Topic

[adrieng1977]

Well here is the usual battery degradation topic.
To start with, I have a 05/2019 LR Model 3.
I have been tracking the data since pretty much the beginning, first with TeslaFi then with an in house solution Teslamate.

I am aware that the BMS can underestimate the actually max battery charge and the the BMS does a pretty good job at handling the battery.

I have read enough out there to understand that there is no magical remedy to bring the capacity back to max but i am getting to a point where i am worried.
I usually drive with % and not mileage. I use the data from Teslamate to give me an idea on "how much" i can drive with a full tank.

My driving habit are a bit all over due to covid and based on tesla recommendation, i was charging and toping off the battery on a daily basis up to 90%.
I recently changed to 70% just to see,

The reason for my concern is that there has been a constant degradation on max performance pretty much since March 2021.
It came back up a bit in june but then have been decreasing constantly up to now having only 268miles. This means that i am currently at 86% capacity after 30k miles.

this chart shows the charging habits. I've never really charged to 100 not been below 10%.
I also like this one to see if software could be a reason for decreased charge

I am really just looking at either
1. this is common and should not be worried much about it?
2. things to possibly to do (i keep reading battery calibration is useless)
3. what other people have experienced when taking the car to tesla and asked for a battery checkup.


This is what tesla told me recently

Concern: Customer states: Please perform battery health check, wants to check if degradation was
normal

Technician reviewed vehicle log data and performed diagnostic of high voltage battery and related
components. No hardware faults or abnormal alerts present. Technician found when the battery is
consistently kept charged within a narrow window that estimation becomes less accurate and tends
to underestimate the true capacity of the battery. The result is an incorrect reduction in the displayed
range estimate. This does not affect the true range of the vehicle, as the true range is based on
physical measurements and not software estimates. Using the HV battery in a narrow range is best
for conservation over time of the capacity, even though it can lead to underestimated calculated
amp-hour capacity (CAC). We recognize the inconvenience and negative user experience
associated with this incorrect and reduced range estimate, and are constantly developing more
accurate estimation algorithms to improve experience overtime. We recommend switching range
display from miles or kilometers to percent (%). This setting, coupled with trip planning when needed,
will mitigate this inconvenient issue. Customers who have made that switch have reported better
overall ownership experience

I feel this is more an "not at fault" answer just so they dont get bombarded with requests and what not.

I agree that driving with % on is better. But i still need to get an idea whether i can drive about 300miles on a full charge or only 200. that makes a huge difference in planning when doing long trips.

My concern really is that based on what i have found out there battery degradation is expected but should stabilize, but i dont think mine is stabilizing.

Anyways thank you for those who will answer and sorry to annoy the typical user that will answer "do you own research" (which i've done)

 

[adrieng1977]

One last thing.
I read that the BMS re-calibrates when put in deep sleep.
Based on this diagram the car has been sleeping so the Teslamate app has not been "bothering" the car much

 

[GtiMart]

I think you'll get the usual answer to your usual question... Here's my "battery report" from TeslaFi:

I have around 24000kms after ~20 months. I usually stay between 55-85% SOC as I like the peace of mind, and I like to have access to most of my power.
Each of the times you can see my range go back up (after dipping below average) corresponds to an attempt on my part to adjust the BMS following the steps indicated in the main thread around here. I've let the car sleep at various lower SOCs overnight, as low as 15%, and I've charged it to 100% at least once. the adjustment never happens directly, it comes after a few charges past the effort.

Since you're charging every night, I think you are having the same issue I had. I suggest trying out the steps outlined and seeing what happens after a few weeks.

 

[SilverSp33d3r]

Data point
2019 SR+ Was “240” miles advertised new.
Highest charge ever seen at 100% - 236 Miles
Average charging between 80-90% weekly
100%-10% Run every 6 months
Current rated range at 100% 209 miles
19500 total miles.

 

[adrieng1977]

I think you'll get the usual answer to your usual question... Here's my "battery report" from TeslaFi:
View attachment 711970

I have around 24000kms after ~20 months. I usually stay between 55-85% SOC as I like the peace of mind, and I like to have access to most of my power.
Each of the times you can see my range go back up (after dipping below average) corresponds to an attempt on my part to adjust the BMS following the steps indicated in the main thread around here. I've let the car sleep at various lower SOCs overnight, as low as 15%, and I've charged it to 100% at least once. the adjustment never happens directly, it comes after a few charges past the effort.

Since you're charging every night, I think you are having the same issue I had. I suggest trying out the steps outlined and seeing what happens after a few weeks.

Perfect gonna try that.
not gonna charge the car until it reaches 20% and hope that helps. Thank you

 

[adrieng1977]

Data point
2019 SR+ Was “240” miles advertised new.
Highest charge ever seen at 100% - 236 Miles
Average charging between 80-90% weekly
100%-10% Run every 6 months
Current rated range at 100% 209 miles
19500 total miles.

So you about just like me. You have 87% max battery usage.

 

[ScottFrancis]

Another data point, 70,000 miles, 2018 AWD LR M3. 268 max range (86%) at 100% charge based on 310 rated.

 

[SilverSp33d3r]

So you about just like me. You have 87% max battery usage.

Yep. However once I was updated to 2021.32.22 my app showed 209 at 90%, then less than 20 min later I got in the car and it dropped to 190. I’m pretty sure tesla is just hiding capacity and it’s not actually gone.

 

[impastu]

Are there any good threads in this larger battery discussion that share any empirical data on "ideal" daily charging limits? Since Tesla removed the recommended daily charge limit I'm wondering if there is an ideal other than < 95-100%

 

[WhiteMountains]

The ideal daily charging limit is 80% to 90%. 90% is fine. 80% is sometimes a bit better if you don't actually need the extra charge. I've been using 80% since I got the car over 3 years ago and I am seeing similar total degradation as above (87%), but I have not been paying much attention to this.

 

[Candleflame]

Down to 440km on my 2019 long range. Often do narrow cycles with keeping the car at 60% but also lots of roadtrips with deep discharges. Switching to % isnt helpful because you only get the kwh the bms allows regardless of how much% thr battery originally had. Could i recover a few kms by charging to 90% all the time? Possibly. Do i still have a ton of degradation? Definetly. 15% is too much for a 2yeat old car with only 40k kms and 13% or 15% doesnt change that.

 

[impastu]

Down to 440km on my 2019 long range. Often do narrow cycles with keeping the car at 60% but also lots of roadtrips with deep discharges. Switching to % isnt helpful because you only get the kwh the bms allows regardless of how much% thr battery originally had. Could i recover a few kms by charging to 90% all the time? Possibly. Do i still have a ton of degradation? Definetly. 15% is too much for a 2yeat old car with only 40k kms and 13% or 15% doesnt change that.

How do you define a “deep discharge?” <10% ?

 

[Candleflame]

How do you define a “deep discharge?” <10% ?

100% to 1 to 3%. with additional multiple 90% to <10% charges the same day.

Deep discharges are due to lack of charging structure and ever dwindeling rated range.

 

[impastu]

100% to 1 to 3%. with additional multiple 90% to <10% charges the same day.

Deep discharges are due to lack of charging structure and ever dwindeling rated range.

I’m no expert but would have thought that frequent extreme cycling like that would accelerate effective capacity degradation similar to iPhone. Some from the delivery board (@Ohmster @cwanja @jebinc )
may have better view or know someone who does.

 

[Candleflame]

I’m no expert but would have thought that frequent extreme cycling like that would accelerate effective capacity degradation similar to iPhone.

Sure, but even if you double your cycling stress then i.e. a 30k km would just be a 60k km odometer which still shouldnt have 15% degradation. And cycledepth doesnt have any significant benefit when doing less than a 90% depth of discharge. I.e. the difference between 100% and 90% is huge, but the difference between 90% and 80% isnt really that significant. And anything less than that is pretty equal compared to other stuff i.e. heat related degradation. And remember when you do a 100% to 5% discharge you are only cycling 91% too.

I dont actually think it happens that often, and sometimes i dont charge to 100% either but start from 90%.

I.e. my car has only charged 15x to 100% in my 2 years of ownership. Essentially 1 roadtrip/month with a few breaks.

I'm more worried about living in the tropics where it is always hot to be honest (my battery is always >25C), and that is part of the reason i keep the battery at 50-65% and dont want to charge to 90% all the time for a few months. I will do it when I move south next february though and then you guys will be the first to find out what happens to the range.
May help us understand the BMS better if I get a restoration of more than 20-25km. I doubt it though. My range has never yoyoed.

 

[jmaddr]

But i still need to get an idea whether i can drive about 300miles on a full charge or only 200

There’s only one way to do that. Go drive. Seriously, go drive and keep the consumption around 245 Wh/m. Drive as far as you can and keep the consumption rate steady at 245 and then do the math and extrapolate to 100%. If you could do 100-0 that would tell you without math, but so would 50% drop and then just double. Since 245 is the reference consumption (Well, at least I think it is for the LR. Teslamate will tell you what the “ideal efficiency” is in the efficiency tab. For my performance, it’s 245whr/m so that’s why I said 245) that’s what the miles are based on. I say drive as far as you can as if you only drive 10 percent, percentage error becomes greater since percentage is reported in solid integers.

 

[Candleflame]

Something we do know is that cycling depth is probably largely irrelevant for Tesla batteries as evident by many fleet teslas which like to do deep discharges and recharges to 100% in short amount of time which apart from the supercharger calibration issue leading to premature degradation due to charging beyond 100% doesnt significantly harm the battery.

 

[adrieng1977]

Just wanted to report on the experiment:
For 3 cycle charging i did:
1. not charge the car until it hits close to 20%
2. make sure to let the car sleep as long as i can
3. charge to 100%

Minimum charge before the calibration : 265miles @100%
current went back to 282@100%

I can report the battery estimation increase quite a bit and i am hopping for it to increase more.

So my conclusion is that even though tesla recommends to charge it every night, it is probably not the best for certain type of driving like mine which is not lots of miles on a daily basis.

For what i have read, the BMS needs to be able to read the battery state at different level to properly do its job. If I always let it measure at only 1 or 2 data points, it will improperly estimate.

I will see if it reaches higher levels. I will not charge to 100% for the next cycle but until 70% unless i know i will drive far, and i will not charge every night unless it reaches less than 40%.

We will see what happens

Thanks all and sorry i did not answer earlier. i am not getting notifications and forgot about this while doing the experiment.

Adrien

 

[svusa]

2018 Model 3 LR:
90% charge used to get 290 miles in 2018
90% charge used to get 284 miles in 2019
90% charge used to get 278 miles in 2020
90% charge gets 268 miles in 2021.

I have observed noticeable degradation after a software update that makes me believe that Tesla might be like Apple limiting battery performance through software for whatever reasons they have.

Telsa tech confirmed that warranty only kicks in after a drop below 70% retention efficiency from original specs.

 

[SilverSp33d3r]

I personally think tesla is “limiting” to allow us to have a pretty substantial buffer below the 0 mark.

It’s quite strange, the more I drive my SR+ the more miles I have available at 90%. I’ve been driving more due to the safety score and my range is going up?