pretty good.
I would take me over 2.5 years to get 18,000 plus miles. In that time to only have a 7 mile drop would be fantastic
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Keeping an Infrequently Driven LFP Happy
- Thread starter PianoAl
- Start date
I would take me over 2.5 years to get 18,000 plus miles. In that time to only have a 7 mile drop would be fantastic
RichAZ/CapeCod
Member
Interesting thread. Wifey and I have a MY LR (lease, buying another MY LR next November) and picked up this M3 SR end of August 2022. My dilemma is a bit different. We use the M3 for most of our driving, the MY for trips. So, for six months out of the year we charge the M3 to 100% once or twice a week. No problem.
We’re “snowbirds” (AZ~Cape Cod). Early May we return to the Cape in our MY and the M3 will sit in our garage (south of Tucson) till end of October, when we return to AZ. Plan on keeping the SoC to 50%, with the car plugged in, while we’re away.
When we get back I’ll make sure to charge the car up a bit more frequently (every time we drive it) for a while to 100% to have the BMS properly reset. Don’t think this will create a problem as the M3 is our “local” use Tesla.
Not gonna get crazy about it at any rate.
Rich
We’re “snowbirds” (AZ~Cape Cod). Early May we return to the Cape in our MY and the M3 will sit in our garage (south of Tucson) till end of October, when we return to AZ. Plan on keeping the SoC to 50%, with the car plugged in, while we’re away.
When we get back I’ll make sure to charge the car up a bit more frequently (every time we drive it) for a while to 100% to have the BMS properly reset. Don’t think this will create a problem as the M3 is our “local” use Tesla.
Not gonna get crazy about it at any rate.
Rich
Just over 6 months now. Bought it with 10K miles on it (March 2022 build) and it indicated 267 or 268 miles at 100% when I purchased it.
These ”degradation zones” is a matter SOC vs (long) time. To make it easy we can think that calendar aging happens only when the car is not used. This not connected to cyclic aging.
For cyclic aging we do not se any ”zones”.
The lowe the SOC is during cycling, the better.
Look at the blue line on the right LFP chart.
25C (77F) is probably about what you have in a garage or outside if not in a hot climate in the summer. At least not warmer in average.
100% is even sliiiightly better than 80-90%.
In high ambient 100% is worse than 70-80% but not extremely worse.
At 50C, 80% might cost you 13.5% degradation in the first 10 minths but 100% would cost you 15% degradation.
100% is sliiiighlty worse, but the increase in degradation is not huge, more like a 10% increase.
The phenomena of seeing lower degradation at 100% in normal ambient is quite common in different lithium ion chemistrys in the research reports.
Lithium ion have much higher self discharge above 80% and at least some of the research reports says the “leak current” counteract the calendar aging by the flow of ions or electrons.
This seems to be the most thorough post out here on the M3 LFP battery so I thought I'd post my observations/findings on my 2023 so far.
At the end of the day, I think the range on this car is deceptive... Because you charge to 100% often, I think it makes it very difficult to compare to NCA battery cars. It seems like range is more affected by driver and weather input vs the buffer you have to account for. Curious how the two cars actually compare in a recommended charges and actual range comparison. (I actually think this thing gets the same real-world mileage as a M3P or an older M3LR).
AAAAAAnnnnyyywwwayyy - I've had my car since Dec 22 and this is what I've noticed about battery degradation:
That "Calibrating" function whenever the battery gets to 99% seems to be key here. Plugging it in once a week ensures the BMS is recognizing the max charge of the without allowing it to sit and degrade on its own. In 3500 miles of driving and charging so far, I only noticed a drop in the estimated mileage when I went long periods without driving or charging much. As a result, my range dropped a little until the next time I let it do the full 100% calibration. After 3500 miles it now says 271 mi vs the 272 I got it at new. I'm happy.
And I think this is the key. Letting the BMS do its thaaang. Graphs and energy consumption and all that is kinda irrelevant as it's just driving the thing vs charging. So that "Calibrating" to 100% is ensuring the battery still knows where 100% is with relative accuracy, aka what everyone here is talking about with the bottom end - would rather not be caught out with a dead battery that still shows 5%.
I think better safe than sorry. At the end of the day, just use the car. Using it and charging as needed should be fine. If you can, every 1-2 weeks, top it up, but LET IT CALIBRATE. For road trips and all that just charge as needed and don't sweat it (full or partial charge). I feel like the weekly recommendation is primarily to protect cars that sit.
At the end of the day, I think the range on this car is deceptive... Because you charge to 100% often, I think it makes it very difficult to compare to NCA battery cars. It seems like range is more affected by driver and weather input vs the buffer you have to account for. Curious how the two cars actually compare in a recommended charges and actual range comparison. (I actually think this thing gets the same real-world mileage as a M3P or an older M3LR).
AAAAAAnnnnyyywwwayyy - I've had my car since Dec 22 and this is what I've noticed about battery degradation:
That "Calibrating" function whenever the battery gets to 99% seems to be key here. Plugging it in once a week ensures the BMS is recognizing the max charge of the without allowing it to sit and degrade on its own. In 3500 miles of driving and charging so far, I only noticed a drop in the estimated mileage when I went long periods without driving or charging much. As a result, my range dropped a little until the next time I let it do the full 100% calibration. After 3500 miles it now says 271 mi vs the 272 I got it at new. I'm happy.
And I think this is the key. Letting the BMS do its thaaang. Graphs and energy consumption and all that is kinda irrelevant as it's just driving the thing vs charging. So that "Calibrating" to 100% is ensuring the battery still knows where 100% is with relative accuracy, aka what everyone here is talking about with the bottom end - would rather not be caught out with a dead battery that still shows 5%.
I think better safe than sorry. At the end of the day, just use the car. Using it and charging as needed should be fine. If you can, every 1-2 weeks, top it up, but LET IT CALIBRATE. For road trips and all that just charge as needed and don't sweat it (full or partial charge). I feel like the weekly recommendation is primarily to protect cars that sit.
LFPs degrade a lot slower than NMC batteries. I was down a mile on estimated range even after the first drive on my LR
Similar situation here. We are going to leave our M3 LFP for 6 months in Oregon around 10 deg C. Based on the SOC based degradation charts/research I have seen, I also plan on leaving the car plugged in at 50% SOC.
To enable the BMS to balance the cells during our absence, I plan on charging to 100% every couple of months via the app and then use sentry mode or HVAC to drift down to 50% again.
RichAZ/CapeCod
Member
Back in AZ from Cape Cod. On the road, using the Tesla app, I directed the mobile connector attached to the M3, which sat at 50% for around six months, to charge the EV back to 100%. Did this 24 hours before arriving at home in AZ. It took just about that much time for the car to get to 100%. So far, after two rides, car seems none the worse for wear! 100% indicated 264 miles range after 7,500 miles and over a year of ownership (August 2022 pick-up).
Rich
Rich
One thing that's odd to me about these LFP batteries is that the ones kept below 70% most of the time (even for extended periods, like @RichAZ/CapeCod) experience practically the same degradation as those that are kept at 100% all the time, at least according to BMS / the car's displayed range at 100%. That doesn't line up with the graph @AAKEE posted, which indicates that LFP batteries kept below 70% should experience about 40% less degradation (about 3.5% over 9 months vs about 6%).
Kind of disappointing that I've gone through all this trouble to keep my SOC well below 70% the vast majority of the time, only having it above that for a couple days at a time when I charge to 100% once or twice per month, yet others with cars of the same age as mine that always keep theirs at 100% and have 5 times as many miles as I do have roughly the same miles displayed at 100%. Don't get me wrong... I actually enjoy trying to optimize my charging habits for long term battery health, so it's not a burden for me... I'm just disappointed that I'm not seeing any results of those efforts.
Kind of disappointing that I've gone through all this trouble to keep my SOC well below 70% the vast majority of the time, only having it above that for a couple days at a time when I charge to 100% once or twice per month, yet others with cars of the same age as mine that always keep theirs at 100% and have 5 times as many miles as I do have roughly the same miles displayed at 100%. Don't get me wrong... I actually enjoy trying to optimize my charging habits for long term battery health, so it's not a burden for me... I'm just disappointed that I'm not seeing any results of those efforts.
RichAZ/CapeCod
Member
Anecdotally it would seem that how you treat these LFP batteries matters not much. None the less I would tend to lean toward the conservative "let's be careful with the battery" group. Can't hurt and might (just might) actually help.
Rich
First of all, there might be differences for the latest batteries from the research reports we can read about today.
From history we know that some of the basics do not change much so it still very probable that the basics still apply.
One thing that could change is the exact limit for the central graphite peak. I think it can vary slightly depending on the amoujt of some chemistries in the anod (or maybe the cathode).
I still would guess that it is in the whereabouts of 72% true SOC. So as far as I can estimate 70% displayed or below should be fine.
In the same way the LFP BMS has a hard time judging medium SOC’s it is possible that the capacity estimation ia not that easy.
Maybe the BMS need a series of full charges and a ”BMS calibration” to estimate the capacity better?
Do you use sentry?
If possible have it off on nights so the BMS can measure the OCV.
Charge full, let it sleep at lesst a couple of hours, then try to het the SOC down to ~10% or less, let it sleep there.
Charge full, let it sleep.
A series of these might help the BMS to better estimate the capacity.
This is teslaloggers data for 2021 Model 3 SR+ with the Lfp battery.
I’m not sure why there is two batches or data. It might be different wheels selected, for the model S plaid it is the same thing (wheel selection dependent).
We can see that the lowest degradation cars seem to loose about 2.5% for 20K km ( roughly one year I guess).
For the ODO, LFP cars is supposed to loose almost nothing due to cycles.
Remember, the average LR/P car witj lithium ion cells loose 0.5% or so to cycles each year. And the LFP has a fraction of that.
So the miles is not a thing for comparison.
The other way around, we have said that people with LFP cars might need to do the ”at least once a week” procedure to keep the BMS in track.
As you seem slightly unhappy with the situation, I think doing the BMS calib. As per above might be a good idea, and during this time, charge full often. Let the BMS see the end points of the battery.
On the other end, I know a guy using all of the battery every day on a Y LFP. Charge to 100% every day.
He arrives home with single digit or 0% or slightly below. Actually he got stranded one day from the BMS overestimating the capacity by about 1.5-2% as it seemed.
Another day he arrived home but the car was out of energy and also drained the LV batt.
From that it was quite easy to undersrand that ecen if this guy do 100% to zero drives every weekday, the BMS was not able to judge the capacity very precise. The error was overestimation despite practically giving the BMS a BMS calib every day.
It is possible that this is valid for the other cars you compare with.
I do not have any data to show right now but from what I have seen it looks like the low SOC strategy actually work well with the LFP’s on the swedish forum also anong the friends using LFP (very few LFP:ers around but still a couple).
I will try to check a little and see.
Follow the science. Your battery very probably is better off than the other people's, you just don't see it yet.
I thought the same was true for me, with 22LR with NCA. Original range 358. I was seeing extrapolated 340 miles (170 @ 50% displayed) after 15 months and was a little disappointed at the degradation as I almost always kept SOC <= 50% displayed. It was probably BMS. A road trip starting with a 100% down to 20% and more recharges up to random numbers between 50% and 55% triggered a BMS recalculation and estimate is 344-346. 345 gives 3.6% degradation after 16 months, a great result. And given that calendar aging goes as square root of time, I'm pretty confident that my capacity will stay good for long term with current habits. Coming into a cooler season capacity will likely stay high until next summer.
Since you have LFP, the estimation of state of charge is more difficult especially in the center of the range---so both your range and your comparator's range estimates are noisy.
Follow the science and the superiority will eventually prevail.
You and I are in the same boat. I kinda enjoy optimizing things, but it might be simpler to always charge to 100%. Worse, this backup car will probably never need to go on a trip, so why am I optimizing?
Do you have any links to the reports of the same degradation when kept at 100%?
I don’t think it’s a BMS calibration issue, or any issue at all with my car, as I have not come across any LFP cars with more than a rounding error’s less degradation than me at the same age. I don’t use Sentry at home and always leave my car to sleep at different SOC, including 100% every couple weeks. The mileage loss is very steady and predictable with no big drops, which further makes me believe calibration is good. I just find it odd that the difference between the best and worst LFP cars of the same age is only about 2 miles of displayed range. Tell me displayed miles at 100% of an LFP Tesla and I can probably tell you the month it was purchased with a maximum error of 2 months. Either SOC barely makes any difference to calendar aging of these LFP cells, or Tesla BMS is using a preprogrammed degradation curve.
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Hope so. You could be right that it’s just too early to see large differences, as my car is only 10.5 months old. Will be interesting to see where I am at vs others after a few years.
Unfortunately, no one is making degradation vs time charts, but I made my own using data from cars that were connected to TeslaFi within the first few hundred miles. When people post their charging habits and displayed range here or on Reddit, I often private message them to ask when they purchased the car, and then cross reference that against my chart, and I have yet to find a car that significantly deviates from the average, no matter their charging habits. Multiple people that keep SOC at 100% have been right around the average for the cars age still. The chart is in this post: Model 3 SR+ LFP Battery Range, Degradation, etc Discussion
Thats just about what I am talking about.
If my thoughts about the BMS having a hard time judging the real degradation Tesla might have used a scheduled reduction of range.
It would explain the similar range loss between your car and the others.
It would problably explain the BMS overestimation from the guy using 100-0% every day.
If you are unhappy or lost belief in that the low SOC strategy works for LFP, then a BMS calib. including to follow the 100% at least once a week might help.
(The 100% at least once a week has been my advice to all LFP owners.
You almost said it yourself
So far I haven’t seen any calendar aging test that do not show that lower SOC causes a lower calendar aging.
many researchers do npt give us the resolution we would like.
