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Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
- Thread starter KK_RedM3
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The 310 claimed in 2019 was with the 18 wheels. Heck the new 22 only has a epa range of 315 and it has a bigger battery than the 19. I believe the rated range with the 20s was 290. The BMS, which reports range, is notoriously inaccurate when measured in the single digit to low double of miles accuracy. Your car sounds very healthy for 2019.
Yes, I have. I have followed the research/science about battery technology for quite long.
There is no data supporting the theory that 100% SOC us better for the battery itself.
(There is one research report from 2021 that say 100% is the best and that LFP’s will hold up for 100 years. There is a lot of strange things about that research report.
There are good reports, and there are questionable reports. This one is questionable.)
I do not say that 100% SOC is very bad for LFP. Most probable they hold up better as they can withstand 100-0% cycles without much degradation as LFP are not sensitive to the depth of discharge.
So, LFP will hold the capacity ok, but if we are talking about what is best for the battery cells themself, lower SOC would ve better. In this actual implementation it is probably better to follow Teslas advice to make sure the BMS know the SOC and reduce the risk of getting stranded because of running out of juice…
You've already gotten the answer, but I'd like to add that charging to 100% is hard on the battery. Don't do it unless you need that extra 27.8 miles for a trip.
I do get a sense of double-speak when hearing some of Tesla's official statements. I feel it's a bit like my local oil change place that says I need to change the oil every 3k miles. Always has me wondering, is it really best for the car, or best for you?
There's a lot of battery research on LFP, NCA, etc. as it pertains to grid storage situations (wind farms, solar farms, etc). Data Center UPS backup systems let alone phones, computers and what not.
I personally feel like the 100% recommendation on the LFP is simply so the car knows how to determine when the battery will be dead. So when Tesla recommends 100%, it really is best for the customer experience. The trade off between a slightly more degraded battery is never sitting on the side of the road because you thought you had 5% left. To me, that makes perfect sense.
However, if I know my ranges I'm driving and my charging times, I could comfortably only charge to 100% once a week to let the system calibrate and be on my merry way.
Tesla's only hurdle is getting past the 100k mile battery warranty.
Of course I have read the manual. If my last name were Tesla, I would write the same, because I would want to make sure that the battery does not go down to 70% within 8 years or 160,000 km = 100,000 miles, i.e. within the warranty limits.
But as I had written, I'm asking for 20 years and 300,000 miles. Forget the manual in that case.
From a point of view of pure physics and chemistry it is possible, but unlikely that keeping the battery at 100% is best in the long run. My guess is that the optimum everyday charging target is somewhere between 80% and 95%, but I would like to know it more precisely.
It is also pretty clear that you should charge to 100% before any long-distance drive and maybe also once per week, to recalibrate the battery management system. So much we know.
I've literally been there, stranded on the road with 5% reported left on an NCA Model S. After that incident the battery immediately lost a small chunk of reported capacity (on top of its existing degradation), I presume from deep discharge. At first Tesla service said the battery was still within spec, I pushed harder, then they actually looked closely at the car's logs and approved a warranty replacement.
So I would say helping the car maintain an accurate view of battery SoC is worthwhile, both for Tesla and the owners/drivers of the car. But I appreciate the info that even for LFP charging to 100% daily is probably overkill!
For the longevity of the battery cells, you probably need to make sure the calendar aging is quite low to keep the batterys capacity ok over 20 years.
The cyclic aging is most probably not an issue with LFP cells. I guess you will get about 200 miles on a full charge in average? That would mean that you need 1500 cycles to reach 300K mi. Not a problem at all for LFP’s, not even close.
From all Ive seen about LFP they also like to stay low for minimizing the calendar aging.
A caveat is that we havent seen research on the absolute latest LFP but the chance that a specific chemistry change totally over a night is low.
The ”step” we see on NCA and NMC is present also on LFP, but placed a bit higher up on SOC(about 70%). I guess it is the same phenomema(central graphite peak) as with NCA, only placed further up.
I would charge to 100% once a week as Tesla say, but I would not leave the car at 100%. I would select the 100% begore a drive that lowers the SOC. Also, I would set the charge to be finisched just in tine begore the drive.
As LFP is not sensitive to big cycles or 100% SOC that part is not an issue but leaving the battery at high SOC would probably cause higher calendar aging, specially in hot climate.
I would not think it was a deep discharge issue. First of all, Teslas Bms shut off the battery before going below the minimum voltage.
Second thing is that lithium batteries is not sensitive to low SOC. Not at all, as long as the voltage is kept above the mininum level.
The third thing is that the research shows that they also are not that sensitive to discharging below the minimum voltage. Damage could happen but it was not very much in the research and not every cell degraded from the over discharge.
I would guess that your BMS was a little off track and thought the capacity was higher than the real capacity.
If discharging to very low SOC or until the battery shut off due to low valtage limit the BMS finds put about the miscalculation and lowers the calculated capacity (nominal full pack). This will look like you lost a bit of the battery that day, but in real it was lost earlier but the BMS didnt take notice.
I have/had a similar behaviour, I only charge to 55% most times to reduce the calendar and cyclic aging. I have had a nominal full pack higher than many had in a new M3P after 15 months and no loss of range.
Last sunday I did the opposite to most others, I actually tried to get a lower max range and lower nominal full pack. I was curious about the true capacitu of the battery.
I drove the car down to -2% SOC, the next day I had ”lost” about 1.5kWh and from that about 10km range.
As I’m back to daily 55% the nominal full pack and the range is climbing back up right now, so I guess ill see the same values as before. This means that my BMS calculates the capacity slightly high and that there probably is about 1.5kWh below 0% SOC that actually isnt there.
I am at that stage where the range is increasing...sometimes more than is mathematically possible ! But I enjoy it
so I won’t be trying to calibrate downwards 
Expecting a M3LR in May. If can attempt to summarize the most important advice I'm seeing here for optimal battery care, it would be "don't leave the battery at a high state of charge for extended periods of time in hot weather." Is that the most important bit, or am I missing something else?
Makes sense, quite possible the issue was already there and running it down to "5%" merely exposed it.
AAKEE, in your graph...
what exactly does graph (d),(e)&(f) show?...are they batteries left in storage and nothing else? Because in car use, storing for 10 months @ 50c, makes no sense.
Also in the key, all the storage times are different...so how do we compare the different batteries ?
Yes, they show the degradation (capacity loss) from time. They leave tge cells at the SOC points and regulary test the capacity by charge full and discharge and measure the capacity.
Capacity loss is more or less cumulative so a car that is driven 10.000 miles over the first year probably is used about 250 hours (40 moh avversge speed) for driving and maybe 300 to 1000hours when charhing.
The rest of the time, about 7000 to 8000 hours the battery do nothing else but waiting ( = the same as in storage).
So for one year with 8760h, the battery ages like calendar aging for about 85-90% of the time.
The fact that the time in the graphs is not exactly the same is not very important. The picture show the principle. One can use the 9.X or 10.X months value as the one year value for a car. Even if it would be possible to make a quite exact calculation, a car that is used is often hard to know the average SOC on, and hard to judge the average cell temp.
You can approximate the degradation for 20, 30 ir 40C, but the hard thing is to know the average cell temp(at least if hou do not have scan my tesla or something showing the cell temps.
The cell temps is not the same as the average outside temp as a car heat in the sun and the cells get heated from driving and charging.
If you still would like compare different batteries you can calculate the (for example) one year point.
The research/science use the square root formula.
If you use 1 year as the comparison, 9.3 monts is 9.3/12 of a year. The square root of (9.3/12) is 0.88. The degradation at 9.3 months is 0.88 or 88 % of the 12 month value. If the 9.3 month value is 5%, the 12 month value is 5/0.88.
We can run this on two points in the chart.
If we have 5% degradation at 1.9 months, how should the degradation look at 9.3 months? Square root 1.9/9.3 = 2.21.
The point at 1.9 months is slightly above 5, so maybe 5.2% or so?
5.2 x 2.21= 11.5%.
A look in the chart show us that the answer is not very far from 11.5%.
. I will chew on this for a while...and maybe get back to you So, after 20 years, what degradation could you accept? 30% total, of which 25% comes from calendar aging?
Square root of 25 is 5, so your maximum degradation during the first year should be 1/5 of 25%, or maximum 5% the first year.
You need to find youself a point in the LFP degradation chart that do not exceed 5% for the first year. That includes estimating the average temp, perhaps average ambient temp +5C. For example, 25C, and use the chart as is( 9.3months = not very long from the 1 year car use).
We can see that the SOC probably shouldnt be above 70% for that big part of the time.
I did a prognose about my degradation which say about 3% right now, and from last weeks test it sure looks like my battery is very much following the plan.
From what I've read, the least impact on the battery is moderate depth of discharges in the middle of the battery capacity. So a 20% depth of discharge from 60% to 40% would have the least overall impact on the battery (versus 100-80 or 20-0 for instance). Only LFP's need to go to 100 for the calibration, I don't believe the NCA's do. If you need more DOD daily, then work your way down to 20, so say 60-20, then 70-20, then 80-20, then maybe 80-10, then 90-10. I think it's more about staying away from the extremes of high and low but low is less harmful than high. Recommended long term storage values are at 50% charge which leads me to believe 1/2 full is the absolute least impactful on the battery so basically increasing out from there for whatever daily range you need would seem to make sense.
That's kind of my dilemma with choosing between the AWD and RWD (NCA vs LFP). With the NCA being a greater range, staying in a 40% sweet spot is about 70 miles. With the LFP it's about 54 miles. I would rather have the 70. Especially when you consider that driving at freeway speeds, in rain, in wind can potentially decrease your range 30-50%. Also when I do want more range the NCA will charge more quickly to 80% then the LFP will to 100% for identical range.
New Tesla owner here 
. I took delivery of my M3LR in January. I have been to a super charger twice prior to this. The two times before, I charged to 90% and that was equivalent of 322 mi. Last night I stopped off at a super charger. I charged to 90% based on the notification. I live like 2 miles from a super charging station so when I left I noticed that I had 318 mi of range. I thought super strange that my range dropped. Then I woke up this morning and started my car. To my surprise it shows that I had 92% range with 329 miles. Ummm what? I'm pretty sure I'm not mistaken. Has this happened to anyone and is it normal?
. I took delivery of my M3LR in January. I have been to a super charger twice prior to this. The two times before, I charged to 90% and that was equivalent of 322 mi. Last night I stopped off at a super charger. I charged to 90% based on the notification. I live like 2 miles from a super charging station so when I left I noticed that I had 318 mi of range. I thought super strange that my range dropped. Then I woke up this morning and started my car. To my surprise it shows that I had 92% range with 329 miles. Ummm what? I'm pretty sure I'm not mistaken. Has this happened to anyone and is it normal?Similar threads
