PrometheusFire
Member
In the week at mostly starting at 90% its down to 55% or below after around 5 hours counting average 2 survey stops of around 45 min each
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Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
- Thread starter KK_RedM3
- Start date
That implies about 8.5 hours at state-of-charge higher than 55% including while charging (last 3 hours of charging, finishing 0.5 hour before you leave) and while driving. Charging to 10% less would likely reduce that by about 1.5 hours. But if that requires a SuperCharging stop not otherwise needed, that goes the other way in terms of battery degradation, plus costing more time and money.
So it is probably close to a wash in terms of battery degradation, so you might as well minimize the time and money spent with extra SuperCharging stops.
PrometheusFire
Member
3 screen shots from today. Finished charging to 90% at 4:30, preconditioned departure for 5am. 317m showing at 89% in the car.
First screen shot is 2 miles from first survey, second is at second survey and 3rd is back home. All the info there. The 119m left equated to 34%
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I always use level 2 between 5kW and 11.5kW.
I've never needed to supercharge.
I used to charge to 70% or 80% but not leave it at that level for long, however I didn't know about keeping it under 55% so some nights it would be in the 60s. When I go on vacations I leave it plugged and charging to 50%
I'm also in Texas where we had a very hot summer.
Now it just keep it between 20% and 50% and that is more than enough for me for a day.
Did another Vegas to SD trip this past Christmas weekend in the MYP. Obviously, 100% SoC miles is different as always. Made it to Hesperia SC with 18% charge this time while driving faster and heavy car train drafting. A prior time was 3% to Hesperia and charged at Barstow instead.
Anyways, was digging around the web and found this Tesla patent on battery capacity estimation algorithm. While this may not be the exact algorithm used in the Model 3/Y, some of the references made in the patent around OCV and wait times have been mentioned by others on this forum in their discussions with Tesla service which makes me believe this patent is close. Tesla likely using this or a derivative of this algorithm in the patent in modern Teslas.
Figure 1. Typical patent boilerplate for an algorithm type patent to show your control system. Cpu and memory. Nothing interesting.
Figure 2 is about SoC adder/subtracter through Ah vs OCV calca towards the weighting to recalculate a new CAC. Looks like a continuous battle between Ah and OCV method.
Figure 3 shows the flowchart on how it is all calculated including the rest period to capture 1st and 2nd time and examples of such rest periods (eg hours in cold temps, minutes in hot temps). Then the delta calculations.
Weighting formula shows k1, k2 and k3 constants and mentioned as setup to prevent fast response and overshoot. Meaning those who think they can recalibrate within one charge session are dreaming.
Figure 4 is interesting. I need to study this some more. Not sure where there would be error differences as function of SoC. Could this be related to a situation where if a repetitive driving/charging style is used in the middle of SoC range that could result in large error in degradation or calibration?
As part of my day job I review competitor patents and generate my own throughout the year so this patent exercise is ingrained in me.
Enjoy the read.
https://patentimages.storage.googleapis.com/c2/c8/c1/c06272fa7c369f/US8004243.pdf
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Very interesting topic in this thread--I'm still trying to learn more! Here are my stats:
- 2022 M3 LR, 11 months old with 8,058 miles
- I've maintained an avg SOC of about 40% with an avg temp of 60F
- I almost always set a limit of 50% when charging at home, never used a Supercharger
- Battery health (via Teslogic app) shows 8.2% degradation
Well, I know I will ’get some’ for saying this
but in all research the cyclic and calendar aging is very predictable.Even if there is two batches tested, they behave the same despite having different capacity. The span of difference in calendar and cyclig aging in general is quite low.
There really shouldnt be much ”battery lottery” when it comes to real capacity.
The initial capacity seem to differ slightly but it might be the BMS algoritm maybe even more than the real difference in capacity.
New Jersey should mean that you have a Panasonic NCA chemistry battery.
The average battery temp will be higher than the average ambient temp, as the battery heats from driving and charging and also from having the car in the sun.
60F average might be 20C avegarge batt temp (15C + 5C for driving / charging/ heating in the sun). That difference doesnt change it much, just telling for the sake of doing better calculations for other people reading.
If your car is 11 months since you did get it, we could calculate about one year from start of calendar aging?
2.5-3% seems like a fair number.
If the average SOC is correct (most important more or less no time over 55-60%), and the temperature is correctly estimated, Id say your degradation should be around that point.
I do not know how good stats is (if that’s what you use) to calculate degradation.
To begin with, 75.6/82.1 = 7.9%.
The 8.2% calculation is not correctly calculated. This at least put my attention to the professionalism of the program you use.
Next thing, more or less no Model 3 with the 82.1kWh pack show even close to 82.1 kWh new.
My pack topped 81.6 kWh Nomimal Full pack and 82.0 kWh Nominal Remaining.
Most packs on M3P did not go above 81 kWh, I think. 80-81kWh is more average.
Also, I do not know if the M3LR has lower average (like if the M3P did get “selected/matched packs).
It would be more fare to use your starting value. Also, I can not se your present range.
Do you have a graph over the range from new until today?
I would suspect that the BMS could be a bit off, and underestimate the capacity.
I have an average batt temp of 13C and average SOC of 43% or so. (Im at work but have logged data of both SOC and temp down to hundreds of a percent and degrees.
10C will keep the calendar aging at about 80% of the 25C graphs, so 2 years and 2 months from the manufacturing date set my battery at:
(0.8x2.5) x (square root (26/10)) = 3.2%.
3.2% down from 82 = 79.3 kWh.
I have mostly small cycles at low SOC but some 25-30 full charges and 45 Supercharging sessions. So maybe 1-2% cyclic aging. If 1.5% the battery would be at 78.1 kWh today.
The NFP has been around 79 kWh lately but was at 78.2 kWh yesterday.
My NFP was at 81 kWh for a very long time when my calculation said that the capacity should be around 79 kWh.(at this time I also did a 100-0% drive that showed that the capacity actually was 79 kWh)
That is 2.5% above ”the real value”. The BMS was clearly off by 2.5% above.
About at this time my range started dropping, and the lowest NFP I saw was 75,7 kWh.
That is 4% below the true capacity!!!
So in a quite short time I both saw a 2.5% overestimate and a 4% underestimation.
The BMS is back on track, or at least not very far away.
The take away is that my calculation is in line with the tested capacity from the 100-0% drive, so for me the prediction is correct. And it should be this for you as well.
I would guess you havent lost more than your 2.5-3% from the initial true capacity and I guess your BMS is off, or the software you use is not right.
You might wanna do a “BMS calibration” to get the BMS to show the capacity more precise…in my case, I havent bothered as the calibration with different SOC’s etc actually does not increase the real range, instead it decreases it slightly by increasing average SOV and introduces bigger cycles.
Not a problem at all but the only thing it is good for is the owners feeling.
It would be nice to see a graph of the range from new to now.
Also, a full charge from low SOC might better show what range the car really think it has.
AlanSubie4Life
Efficiency Obsessed Member
We have a very limited sample from SMT for the LR.
But from what I have seen they were in the 79-80kWh range at the beginning, in general. Whether that is still the case I do not know.
They only start losing range when they go below 79kWh though (unlike the P which loses starting at around 80.7kWh).
So 75.6kWh is about 5.5% loss, max, may be as low as 4.5%.
I would say the battery degradation of 8% is not real. I think you are suffering from SOC estimation error from only having your BMS work with below 50% SOC values.
My M3P was showing almost 10% degradation when it only had 1000-2000 miles on it. Not real. And it had charged to 50% max majority of time with no Supercharging. I have since done a 600 mile road trip to Cali with it, charged to 100% a few times and Supercharged twice. It is showing 2-3% degradation now.
See below figure from Tesla BMS patent showing example error in SOC estimation.
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AlanSubie4Life
Efficiency Obsessed Member
Thought we had examples from US market too, but not sure. Data are around here somewhere!
Perhaps?
I think I was a bit unclear: All Made in China M3P with the Panna 2170L 82.1kWh that was checked with SMT I am aware of have had low NFP.
(this is a other subject than @citivolus question but still very interesting.)
Thank you so much @AAKEE for your detailed response! Below is a graph of my range from Teslamate as requested. Starting range on 2022-02-16 is 357.73 and the value displayed for today's range is 339.81.
Can you please elaborate on how I would do a “BMS calibration” to get the BMS to show the capacity more precise?
Sorry for the obvious error as displayed in the health from the app I am using (Teslogic). What do people use to get a more accurate value for current battery capacity?
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Thanks, this sounds very similar to my situation and your explanation sounds reasonable. Hope I can figure out a way to confirm on my end!
Lithium batteries will not go up and down in capacity. In practical terms, the capacity will only go down. (There is a self healing effect but we can disregard that in this case).
Your cars degradation (mostly calendar aging) will look about something like this:
Try to see the big picture between the ups and downs. Disregard from the very last drop you have that is very recent.
Before that drop it was about 343-345miles?
358 is the EPA rating, and in many cases the highest range displayed.
Your apps 360.xx is probably a calculated number from actual range/SOC.
Max range shown is about 358 miles and it need 79 kWh to reach that number.
We do not know your top real capacity or top range, but if we use 358 mi / 79 kWh as the starting point, and we se about 345 now, we get 345/358 = 0.964 —> thats a 3.6% loss.
Not at all as bad as the info in the earlier post. I do not know much about the regular starting value in the Long range with the 82kWh pack.
To know the starting capacity you would have needed to read the Nominal full pack value out of the car with scan my tesla or likewise. So we do not know, and can not guess the initial or early value.
I not too sure if it is a good idea to blindly thrust your logging software in any aspect.
I see that there is fault induced in many of these softwares.
I use teslafi, which calculates the max range by division with rounded numbers. The result is a range that differs at least 5km without Scan my Tesla showing any change in the nominal full pack. Logged scan my tesla range can be very static for one month, but the teslafi range jumps up and down.
In Tessie the degradation value seems to be ”adjustable” by the possibillity to set an own starting number, also they call the actual capacity ”useable capacity” so some people think that is the capacity excluding the buffer.
For all my full charges, the nominal remaining has exceeded the nominal full pack with about 0.3-0.5kWh. The full charge range will be slightly higher than the calculated with my car. The degradation might be slightly less then the NFP or range in these apos suggest.
There is a thread here on TMC, ”How i restored half of my lost range”, search for that.
I understand the basics, but I never used that trick as I wrote so it might be better to read there than to having me trying to explain it, without own experience.
Also, as we saw the degradation is probably NOT 8% so you can relax.
Maybe the BMS is not very much off, but from the recent dip it seems to be slightly off on the low side.
No need for a Bms Calibration but it would actually be nice to see the result anyway.
Scan my tesla is good. You get the BMS number directly from the BMS, without any programmer inventing own calculations and own terminology that we might misinterpret.
Still, the BMS is off from time to time so one single check might give us a nominal full pack that is wrong.
(Even scan my tesla can be wrong. The latest scan my tesla app for android show a ”rated full range” that is reducing with reducing SOC. Before the latest upgrade it was rock solid but it is also not correct).
You can calculate the nominal full pack with the energy screen.
Average consumption x calculated range / SOC in absolute numbers = number of watt hours. You should not have too low SOC when doing this as the division with a rounded SOC number introduce an error att lower SOC. Say, 70% and above give a result that is ok.
Thanks again @AAKEE, great detailed response!
Seems like based on Teslamate my current projected range is about 344, which as you said is only about 3.9% from 358, not the original 8+% I feared!
After reading the "How I Recovered Half of my Battery's Lost Capacity" thread, I will try the following:
Charge up to 90% by 1am
Let the car sit for 6 hours at 90%
Drive to work and arrive with about 84%
Let the car sit for about 8 hours
Drive home and arrive with about 78%
Let the car sit for about 12 hours
Drive to work and arrive with about 70%
Let the car sit for about 8 hours
Drive home and arrive with about 64%
Let the car sit for about 12 hours
Drive to work and arrive with about 55%
Let the car sit for about 8 hours
Drive home and arrive with about 49%
Let the car sit for about 12 hours
Then from this point I will resume my routine of driving the car down to about 25% before charging back up to 50%.
Does this sound like a reasonable plan? Will be interesting to see if this changes my projected range after a week or two.
Seems like based on Teslamate my current projected range is about 344, which as you said is only about 3.9% from 358, not the original 8+% I feared!
After reading the "How I Recovered Half of my Battery's Lost Capacity" thread, I will try the following:
Charge up to 90% by 1am
Let the car sit for 6 hours at 90%
Drive to work and arrive with about 84%
Let the car sit for about 8 hours
Drive home and arrive with about 78%
Let the car sit for about 12 hours
Drive to work and arrive with about 70%
Let the car sit for about 8 hours
Drive home and arrive with about 64%
Let the car sit for about 12 hours
Drive to work and arrive with about 55%
Let the car sit for about 8 hours
Drive home and arrive with about 49%
Let the car sit for about 12 hours
Then from this point I will resume my routine of driving the car down to about 25% before charging back up to 50%.
Does this sound like a reasonable plan? Will be interesting to see if this changes my projected range after a week or two.
Remember to leave Sentry Off and Cabin overheat protection (probably not an issue since it's Winter), those two things would keep your car from sleeping. You want the car to sleep, so that it will open the circuit to the HV battery and enable the BMS Calculations.
Thats a decent start. Cold ambient temps will increase the sleep time needed before the BMS will take a SOC open circuit voltage sample.
Another option would be to set the max charge to 90% a fews days in a row and then set to 80% a few nights in a row, then 70% a few night and so on.
But do what is comfortable for you. There is no right or wrong answer.
Based on the filtering Tesla has implemented in the BMS, it will take a lot of samples to move the needle on available capacity calculation.
I have started to spike my max limit up once a month for a few days to ensure my BMS has the best idea of useable capacity for those long road trips where I need it.
Would NCA batteries benefit from occasional charging to 100% to keep the BMS in sync? I.e. similar to the once per week 100% charging for LFP batteries, but less frequent (perhaps once per month)?
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