Tam
Well-Known Member
It does make sense for short-term owners.
By the way, you are not the only one. Tesloop (when it was in business prior to the pandemic) did that too.
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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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By the way, you are not the only one. Tesloop (when it was in business prior to the pandemic) did that too.
Your post pretty well describes the approach I took with my electric motorcycle, especially the running it down to zero bit. And for me this was again in violation of sound advice I was getting off Internet forums about lithium batteries. I actually wrecked the motorcycle after about 3 years, and at the point I wrecked it there was definitely some degradation of the batteries. The motorcycle started out with about 60 miles of range, which I proved a couple of times (One time I had to sit with it plugged in at a gas station for an hour or so until it had enough juice to get me home.). I’d guess the range by the time I wrecked it was around 50-55.
I guess you have to separate out the science from the overall goals you’re trying to achieve. Because I’m really confident that all that advice about not emptying out the tank and not leaving the tank full for too long is all science-based legitimate advice. On the other hand, I would bet that though you lose a few miles of range over the course of 4 years, it’s not like the car will be shot at that point, or even close to being shot. My guess, though, is that if you re-sell the car, a careful buyer would either turn his back on it or knock the price down. Not the end of the universe or anything. But if that happens, I would be the last to try to claim that you didn’t get your money’s worth out of your use of the car. It’s more like with a used ICE, would you rather buy one from the little old lady who only drove it to church on Sundays, or the rip-roaring maniac who was trying to set the world’s record for doing do-nuts on city streets?
I hope you‘re willing to stop in every once in a while and give folks an idea of how your range is doing as time goes on. Sometimes people can get too far into this-is-bad-and-this-is-good mode, and what you can offer is some actual numbers showing how bad (or good) this style of using the car is, and a more accurate idea of how this affects its capability and value.
It isn't 'rhetoric' or 'virtue signaling', or emotion here. It's attempting to translate independently discovered scientific results into practical implications for people to use.
It's clear that if you need to charge every day to 100% and you run it down, you drive very significantly every day. Which means that the amount of time spent at 100% is probably low, as soon as it gets there you need to drive in a short time period and it goes back down. This is better for the battery than sitting at 100% for any significant length of time. Even still, if you lowered the max to 95% that would lower degradation. Or if you made sure that the 100% was achieved immediately before you travel using scheduled departure so the time at high SOC is minimized.
The battery will probably not be damaged in a major way--which I define as catastrophic failure. You will have more degradation than people who drive less and keep the battery max at a lower percent SOC at most of the time. It's unlikely to need full replacement because of major degradation.
Personally, if I were at the edge of the range and needed the full range on a day, which you seem to, I would change the wheels and tires to a more efficient setup (lower diameter wheel and efficiency tire) than the default Performance setup. The wheels will be sellable too.
BTW, 24K miles in a year is significant but not using full range every day: 250 miles * 365 = 91k. So still the direction is to avoid charging to 100% and letting it sit there, as that will definitely enhance degradation vs alternatives, particularly if it is hot.
If you plan to sell in a few years, the state of health of a battery is a primary concern for any buyer obviously so I would still work to enhance the battery lifetime.
The scientific results that have been discussed here show that avoiding the low state of charge is not necessary or helpful for batteries and people who tell you to do that are wrong. So you are correct in not doing constant recharges to avoid low state of charge during your driving day.
( It's only maybe storage at 0% for a long time weeks/months which might hurt with self-discharge, but maybe not). As I've written above, avoiding holding at high state of charge times the time at that SOC is most important. If you can make it from 90% to 2% every day, then that's fine.
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More degradation than someone who only charges to 50% for daily use for sure. But...
It probably won't matter. If whoever buys it doesn't check for degradation, it might not even affect the resale value. If the car is owned by Tesla (you're leasing it), then it REALLY doesn't matter. The battery is a consumable component. Some people's charging habits are harder on the batteries than others, but I wouldn't consider your usage pattern to be "abuse", if you actually need all of that range.
Probably not.
The only thing I'd be worried about, assuming you're not planning on keeping the car beyond 2-3 years, is that if you are barely making it back with range in the low double digits, is that degradation will make it where you won't be able to even do all of the driving your currently do after 2-3 years. To reduce degradation, I'd (1) use the scheduled charging feature and set it to finish about an hour before you depart each day, so that the time spent at 100% is minimized, and (2) set the limit lower if there are any days of the week you won't be driving as many miles, so that it doesn't sit close to 100% for a good portion of those days.
Even if big cycles wear more than small ones, the degradation from this still is way outperformed from calendar aging.
We have a guy with a M3P 2021, (same as mine) at a swedish EV forum that drives 250km highway back and forth every day. he charges to 90% and arrives home with around 10%.
Two months ago the car was at 69K km (43K Miles) and he still have about the same numbers as most other M3P on the forum that have very low miles but use 70-80% daily charging.
This guy arrives with about 10% and it sits with 10% until it needs to start charging to have 90% just before the next days drive. The car never stands long time with high SOC.
This is my Teslafi degradation page, "Nogos" number at 69K km put in as a point at the two month ago value and a straight line. He was initially worried that the car would not hold up for his three years of planned use, but after some posts etc. he relaxed, I think he is quite happy now.
[Edit]Checked with Nogo, now 79K km and 90% charge shows 418km, indicates 464km range at 100%.
Exactly.
Low _SOC is safe. A single cell, or a bettery pack disconnected from comsumers will not have a noticable self discharge. That is the reason that make it possible to store Lithium Ion batterys for long time at 0% SOC (note: not completely discharged, but at the minimum specified voltage set by the manufacturer. In the Tesla li ion case, 2.5 Volt per cell.
But in a car like a Tesla the battery will discharge from consumers that the 12v battery serve, and that get charged by the lithiumion battery.
So in the end, the lithium battery will safely be disconnected by the contactors, causing the 12v battery to drain and get damaged. Lead Acid batteries do not like to get discharged (opposite to lithium ion batteries).
That said, the self discharge/car usage of energy for a car that have sentry disabled and no external apps disturbing the sleep use very little energy/day.
I regularly leave my car for about a week at my job and I actually see the same SOC when firing it up after the week. I use teslafi and teslalogger but these do not disturb my car so my car sleeps more than a day each time, sometimes two or three days.
Tesla say to count with 1% per day, but that is most certain with a big margin to the real life drain.
Yes, one more thing: self drain is higher with higher SOC. When we look a the battery self drain and not the car usage of energy.
This is probably on of the things that make my car not loose any noticable SOC during a week.
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The reason I say "virtue signaling" is someone posted to the forum asking how far he can take it at 0 miles (I dont have it set to %) and I was interested in this too since I wondered how long I really had that day to get to a charger before it shut down on me in the middle of freeway traffic. So as I sat at the charger. Hands trembling since it was a close one! I got on these forums to find out...what range did I have at 0 miles
Some responses were helpful in trying to answer that question but most responses were " I would never do that" IE - How dare you?
As far as the milage I rechecked I have had it for 11 months and 3 of those months I had a loaner while tesla was getting me a replacement part. So really I have been driving this car for 8 months.
To clear up my home charging habits:
I get home later in the day. Plug it in and its scheduled to charge at night (to save $$$) and ready by 8am. I usually depart around then if not then by 9am. If I am departing at 6am I set it to 6am.
When people say they would never do that....it’s because they don’t want to stop in the middle of the freeway...not because they are telling you off.
It’s your battery to do as you please...but as in everything in life there is best practice....by adhering to a few simple rules (which aren’t rules, they are voluntary) you can preserve your battery....just like a careful owner would treat his gas car well and his dog even better
Why don't you gather the data if no one else has it and share it with us? I had to do this with one of my cars (pure ICE model) because I couldn't find any info on this. So I carried a gas can around in the trunk and drove it for over 50 miles after the low fuel warning light came on.
Carry your UMC, appropriate adapters, and a generator in the trunk. Find a road without a lot of traffic, and drive until the car stops moving. Record how many miles you're able to go past 0, then when the car dies, plug in the UMC and start the generator. Charge it enough to get to the nearest SC site.
A new paper on modeling calendar aging of batteries:
settings Open AccessArticle Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation
Some of it is not surprising: the very strong negative influence of high temperatures, and the negative effect of higher state of charge.
The key result in the model in equations 4-8. The main interesting result is that the assumption of aging as a square root of time is not a preferred model, and that a better model is an exponential (important at early times) added to a linear degradation. That's equation 4.
That's somewhat bad news in that longer term the linear degradation is worse than a square root, but the linear part isn't discovered until the exponential has been made unimportant.
The slope of the linear effect (\gamma(SOC,T)), equation 8. has a dependence on SOC. Note the "exp()" terms on right hand side multiplying all coefficients in equations 5-8. Those are the temperature effects: high temperature makes everything worse for degradation.
The SOC effect on the exponential term is more complex than the linear term (5) vs (8). That's a cubic which in figure 5 results in two maximums. Note also the figures are at pretty high temperatures (40 degrees C is very warm for continuous battery temperature). It's faster to get degradation results at high temperatures because everything happens faster.
settings Open AccessArticle Calendar Aging of Li-Ion Cells—Experimental Investigation and Empirical Correlation
Some of it is not surprising: the very strong negative influence of high temperatures, and the negative effect of higher state of charge.
The key result in the model in equations 4-8. The main interesting result is that the assumption of aging as a square root of time is not a preferred model, and that a better model is an exponential (important at early times) added to a linear degradation. That's equation 4.
That's somewhat bad news in that longer term the linear degradation is worse than a square root, but the linear part isn't discovered until the exponential has been made unimportant.
The slope of the linear effect (\gamma(SOC,T)), equation 8. has a dependence on SOC. Note the "exp()" terms on right hand side multiplying all coefficients in equations 5-8. Those are the temperature effects: high temperature makes everything worse for degradation.
The SOC effect on the exponential term is more complex than the linear term (5) vs (8). That's a cubic which in figure 5 results in two maximums. Note also the figures are at pretty high temperatures (40 degrees C is very warm for continuous battery temperature). It's faster to get degradation results at high temperatures because everything happens faster.
Not that new, I've already refered to that before
First of all, they might have a small point with the formula for calendar aging.
Second, other tests of calendar aging show other data, and in many cases it follows the "square root of time" very good.
Third, the difference between their formula and our "square root of time" is not that big. For our amateur calculations I think the square root works very well.
( I did a backwards BMS calib. recently to try to set my BMS from full range to to reflect the actual battery capacity. I think it worked, and now I have about 79kWh capacity according to my BMS. That is very close to my "square root of time" calcs. Using my logged data of average SOC and average temp I should have around 2.6% calendar aging now. The cycles should have worn around1% by now. This should put my battery capacity at around 79.1kWh if I calculate from 82.1 as the new pack number(once did show 82.0 nominal). My BMS calib put it at 79.0, and also a 0% to 100% charge one week ago indicated both 79.0 nominal and also the difference in nominal remaning was spot on. (79kWh -3.5(buffer))
I do not think the above is a coincidence.
There is a tendency for reserachers to use very high ambient temperatures and then draw conclusions like "we accelerated the calendar aging so each week was like one moth(or year).
In reality very high temperature (specially together with high SOC) kills the batteries. This makes the usual square root of time formula look bad, but when we look at researchers that use reasonable temperature, they do not get that behavoiur. The same is valid for using too high C-rate for charge/discharge cycles.
If you look very closely at the graphs you see that the linear part in their graphs actually show that the test points actually do show a not linear line but the curved line that fit the square root quite good. Also, from my point of view they stopped the test very very early in the "linear part". Way to early to make their statement clear.
There is an older report out trying to find a better formula than "square root of time". If I find it, I'll post the link later.
No, its not possible you got "the incorrect battery". You can calculate what your car thinks the battery capacity is with the information in the stickied thread here:
Calculating Your Battery's Estimated Capacity Using the Car's Energy Screen
Re posting here and making this a sticky post so it doesnt get lost. @AlanSubie4Life originally posted: =========================================== (originally posted by @AlanSubie4Life. Original thread this appeared in can be found here: ( 2021 model Y scan my Tesla battery size)...
teslamotorsclub.com
As for "I am not getting anywhere near the mileage" that discussion is in this long 250+ page thread I moved your newly created thread to. Without you even providing any additional information, I can tell you that it is 99.9999999% likely your car has the correct battery, and is performing normally. You can read through some of this thread to see why I say that.
Not that new, I've already refered to that before
First of all, they might have a small point with the formula for calendar aging.
Second, other tests of calendar aging show other data, and in many cases it follows the "square root of time" very good.
Third, the difference between their formula and our "square root of time" is not that big. For our amateur calculations I think the square root works very well.
( I did a backwards BMS calib. recently to try to set my BMS from full range to to reflect the actual battery capacity. I think it worked, and now I have about 79kWh capacity according to my BMS. That is very close to my "square root of time" calcs. Using my logged data of average SOC and average temp I should have around 2.6% calendar aging now. The cycles should have worn around1% by now. This should put my battery capacity at around 79.1kWh if I calculate from 82.1 as the new pack number(once did show 82.0 nominal). My BMS calib put it at 79.0, and also a 0% to 100% charge one week ago indicated both 79.0 nominal and also the difference in nominal remaning was spot on. (79kWh -3.5(buffer))
I do not think the above is a coincidence.
There is a tendency for reserachers to use very high ambient temperatures and then draw conclusions like "we accelerated the calendar aging so each week was like one moth(or year).
In reality very high temperature (specially together with high SOC) kills the batteries. This makes the usual square root of time formula look bad, but when we look at researchers that use reasonable temperature, they do not get that behavoiur. The same is valid for using too high C-rate for charge/discharge cycles.
If you look very closely at the graphs you see that the linear part in their graphs actually show that the test points actually do show a not linear line but the curved line that fit the square root quite good. Also, from my point of view they stopped the test very very early in the "linear part". Way to early to make their statement clear.
There is an older report out trying to find a better formula than "square root of time". If I find it, I'll post the link later.
great info. Of course 1-a*(exp(-t)-1) - b*t can be approximated at early time intervals by 1-c*sqrt(t) Or lots of functions.
You're right that in longer time intervals the physics and results aren't clear for calendar aging in the regime that we would care about, such as 20 degrees C for 10 years. Extrapolation isn't fully valid when all the basic mechanisms aren't fully understood.
What matters is if there is a clear physical principle underlying calendar aging which means that the long term degradation is less than linear or is it linear, and the answer will come from chemistry experiments not curve fitting. Panasonic might know but they aren't telling.
Steve446
Dusty Crophopper, M3 LR 2021 Midnight Silver
Agh... with all your posts I will have to brush up my math(s)
The publications do show I imagine the worst case scenarios for battery degradation but, as has been mentioned by @AAKEE, by skipping over testing at lower temperatures, so far we have few hard data about the best conditions for longevity in the 0-20°C range. Excepting that is the experience from drivers in, on average, cool or cold areas.
Steve446
Dusty Crophopper, M3 LR 2021 Midnight Silver
Have I misunderstood or is it my math neuron needing a reboot? The degradation "curve" from my battery appears biphasic when plotting NFP. Is this normal physical-chemical process or might it be influenced by following a more rigorous low SoC storage (~35% average) and charge to use, from when I got SMT in January? Average monthly battery cell mid temperature17.5 to 26°C. Or is it just as likely to be something else? Just curious!
Battery is an LG M48 NMC.
The BMS guess the capacity, and it is no better than the software values put into the computer. This should not be mixed with the real capacity loss and the real degradation.
Lithium batteries in our cars will only change the real capacity in one way:
- Downwards!
The BMS calculation is affected by a lot of things, causing the range to go up and down.
You also can see that the NFP is more solid than the estimated range. The estimated range (estimated by teslafi or SMT?) seems to vary a lot more than the NFP.
This is because the app or teslafi etc makes an own calculation of the 100% range. This is not a true Tesla value and it vary despite tha fact that the NFP is not varying, so estimated range by an app or teslafi should be taken with a grain of salt.
Disregard short term variations from those range calcs. Use only NFP if you have that value. NFP is not exact but vary much less. Still, this is not true capacity as the capacity only really goes down, never up.
Down below: a period when my NFP was rock solid, no more than 0.2 kWh difference(mostly none). The 80.4-80.6kWh should mean a true range of 506-507km.
Teslafi shows 497-505 km mostly and a lot of variations despite the same NFP.
Have you left the car sleeping to invoke OCV when at 100%? Or you drove it directly to under 55%.
And when at 0% have you left the car sleeping some hour?
To compare, I did drive about 20,5 K mi the first year. No appearent loss of range during the first 12 months.
Now after 17 months I read about 498km/ 310 mi on a full charge, 42K km/ 26k mi.
I did 20,5K in the first year and used 55% as daily charge. Most days 35% SOC would have been enough with a good margin to run ouf of juice.
I use the Tesla WC as well.
If you charge to 100% you will increase the wear of the battery. Both calendar aging willb e higher if it stands at 100%, and the cyclic aging will be higher due to high SOC.
It would be interresting to se your range at 100% SOC( the rangemeter selectable at the battery). It is very probable that your range is considerably lower than the new car range, and lower than mine.
Is it posdible to get an picture of that when just charged to 100% ?
There is no expectation at all that the battery would brake down from one year of 100% SOC but the wear/degradation is probably noticeble.
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