AAKEE discussed this back earlier in this thread along with some real world examples from his own vehicle.
I'd recommend you go back and read that post for more information.
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Favor Low SoC or Small Cycles?
- Thread starter Drinyth
- Start date
I'd recommend you go back and read that post for more information.
Is there such a thing as Tesla Battery Psychosis? But thats probably for a Psychology Forum. At what charge parameters does a Tesla driver loose his/her mind trying to keep "Perfect" charge, "Perfect" battery life and actually use the car for something other than up and down the driveway? Sometimes I feel that we talk about Tesla cars as if they were Traxxas hobby cars. 
How do I squeeze an extra 2 percent, how do I get to 300k miles etc. Most of those asking those questions sell their cars by 100k miles anyhow and buy new ones cause they have that bug and like new things all the time.
How do I squeeze an extra 2 percent, how do I get to 300k miles etc. Most of those asking those questions sell their cars by 100k miles anyhow and buy new ones cause they have that bug and like new things all the time.
Depending on the situation and how you set your charging schedule, its possible to cut the degradation in more than half. Just having the SOC on the right side of the step for most part of the day cut it in half.
In plain text, its not the miles that degrades the battery during the first 5-8 years or so.
For ”miles” we can look at this graph.
All different cycles use the same DoD (10%) in this graph. Theres quite some difference in battery life if cycling low instead of high.
I went for the low SOC approach from the car was new.
Current battery capacity is about 78.6kWh/ 490 miles.
All 8 other similar cars at the same ODO reading has a lower range and the average is 460-465 km at my mileage.
Full range when new was 507km so my car has lost about 3.3% indicated range.
(Last full charhe was 498km, 1.7%).
The average same car (M3P 2021) has lost 8.2% at the same ODO.
I did a 100-0% drive about 6 months ago and measured 79kWh capacity. The indicated range has been off due to the BMS being off, at the moment the 490km indicated is probably quite correct.
I have about 30 full charges, actually charging full right now for a 250km drive in cold weather. I also have 50 supercharging sessions.
So I never needed to waive the fun stuff.
Charging to 100% does not kill the battery, nor does supercharging.
(When using low SOC there is a recovering effect that gain some of the capacity loss, so full charges and supercharging will hurt less in the long run if using the low SOC strategy.).
Does calendar degradation dominate for the first 5-8 years, or until degradation reaches a certain point? In other words, if you can keep calendar degradation low for the first 8 years, is the battery more likely to still have calendar degradation as the dominant component into years 9 and 10 vs. someone who consistently kept the battery at near 100% SoC?
That chart is interesting. It suggests that I could dramatically improve battery life by charging only to say 20-30% SoC, even though the car will not let me set that as its limit. I could do it by using my CP Home instead of my WC however, and setting the WC to charge for only the amount of time required to get the battery to between 20-30% before cutting off the power. I actually do manage the battery in my PHEV in this manner because that car lacks a charge limit I can set on the vehicle side. 0.5 kWh per bar on the battery gauge, and the car charges at 3.4 kW. When I pull into the garage I can therefore calculate the amount of time required to get to ~80%, and I know when I'm going to depart next, so I effectively do both a charge limit AND "scheduled departure" charging on it by manipulating the charge start and end times after every drive. But it's a hell of a lot more manual manipulation than is required to manage the battery in the Tesla. Just like on my Tesla, I'm not afraid to charge my PHEV's battery to 100% if I really need to, but I only do it if it's necessary and I do it about 30-60 minutes before departure. And I've been managing the battery like this since before I even had the Tesla and probably before Tesla even came out with the Scheduled Departure feature.
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If we split it into cyclic aging and calendar aging first.
Cyclic aging is in most cases about the same each year. In some degradation tests the curve is straight, in some (mainly low SOC cycles) the degradation per cycle decreases slightly and for ”hard” cycles it often bends down (more degradation/ cycle after reaching 20% degradation.
To keep it simple, we can look at cyclic as constant. It most probably is almost constant, thats like 0.5% per year or so, in some cases maybe almost 1% per year at somewhere normal dtoving ranges per year.
(I would put my car well below 0.5% per year, du to mostly low soc - small cycles.)
Calendar aging for the average car, with 70-80-90% charging in the early evening arriving from work, would be in the ball park of 5-6% the first year in an average climate.
5% the first year
7% after the second year
8.7% after three years
10% after four years
11.2% after five years
12.2% after six years
13.2% after seven years
14.1% after eight years
And so on.
I usually round up the numbers to whole numbers but to see when we reach 1% per year, I did keep one digit.
Doing high SOC cycles and more miles might give us 1% cyclic aging per year, so in that case we would brake even at about 5-7 years.
The common calendar aging formula is *square root of time(years)* x the first years rate.
It seems very valid for 0-3 years research.
It might deviate from this in the longe run…but for understanding it, I think we can use that formula for long term calcs also.
( teslalogger and teslafi data support these calculations).
My car wit an average cell temp of 13.46C and average SOC (climbing after change of job about one year ago) at sbout 40% will also continue to follow that square root of time. Low Soc and low temp gives quite low rate even the first year.
I am below half of the numbwrs I gave higher in this post.
My battery follows the data from the charts.
This is 5 months, and 40% at 13C would be about 1.5%.
26 months now, so 1.5 x square root (26/5) = 3.4% calendar aging.
Throw in about 0.5 % cyclic per year, and we are at about 4.5%, 78.5/82.1 —> 4.3%.
Absolutely. Its posdible to set the timer so the soc is 20 or 30% when leaving.
But I decided to use the charhing tactics that really do not hinder me to fedl free and not to involve in a system that makes it not fun to use the EV.
I charge to 55% as it is below the step, the best compromize between low degradation and freedom.
It would be pissible to reduce degradation much more, but for me it would not come without making an impact on the freedom etc.
I am happy with my low degradation, it follows ”my plan” very nice so…
Just to make sure that we are talking apples to apples, what's the definition of a cycle in this chart?
For case #31 is a cycle 0-10%
or is it 0-10% ten times?
All cycles in that chart is Full Cycle Equivalent (FCE). Marked on the X-axis scale.
This means that one FCE is the same energy as a full 100-0% cycle.
For 10% DoD, there 10 single cycles in each FCE (10x10= 100%).
When you see 10.000 FCE thats actually 100.000 single cycles.
I'm asking for a simple answer to the question, for which 95% of people reading this want. What's the difference in lifespan. Either in years or miles.
Just your simple statement of "lithium-ion batteries" is an example of naivety. There are big differences between the different formulations. And there is also big differences in how they are manufactured. One-size doesn't fit all.
Are you talking about the reports that ONLY cover 2 years?
Different degradation factors from total lifetime. And a study size of 8 vehicles, well, says nothing to me.
It's actually not possible in my case because I don't have a consistent schedule.
Sure. I think your climate plays about as big of a role in minimizing degradation as your management of SoC levels though. I don't think someone in a hot climate could hope to duplicate your results even with more careful SoC management. 13.46°C average temperature is really, really low and I would expect the car to use the battery as a heat sink for the cabin air conditioning until it reaches at least 20-30°C (and in some climates you're almost always using the air conditioner). I wouldn't be surprised if the batteries for a vehicle parked in Honolulu for example rarely ever go below 22°C and routinely are allowed to go as high as 30°C before the heat pump starts cooling them down.
And there's a big difference between the battery in my PHEV and the battery in my Tesla. If I ever find myself short on battery power in the PHEV, I just have to burn a little bit more gas. There have been times when I had to drive the PHEV unexpectedly and I had the battery basically sitting at empty, but it's not a big deal because I have never had to alter my schedule because of it. But still, 30% SoC in the Tesla covers almost 100 miles of driving, which is more than enough for any unexpected drives in daily use. Would be extremely helpful if they allowed you to set limits as low as 20%.
dhrivnak
Active Member
The one thing you are forgetting is the need for cells to balance. And to balance the charge needs to be above 85% and 90% is better. Below 80% there is little opportunity to balance and your range is then limited to the weakest cell. It can be recovers but that normally takes a few weeks. If you fully charge for trips say 3-4 times a year you should be OK. But if this is an around town car you will notably degrade the range.
Oki, I have no real solution for that, I guess. If you know the next days timings, you could adjust the starting time of the charge each evening?
If it isnt possible, I guess charging only what needed will also do a difference (but the timed charing really could change the average SOC downwards…I guess many people connect the car at arrival at home, and start the charging 4:00-5:00PM, giving the car some 12hrs extra with high SOC each night..
If / when we need aircondition, the ambient is hot here also, otherwise we wouldnt need AC. I have data that my car is most efficient between 20-25C, so not much power for AC could be needed before that. There will be some times when the AC could shuffle heat into the battery, but it is not that often.
I havent seen the heat pump cool the battery. I do not think Tesla does? Cabin overheat protection cools the cabin I guess.
Hot summer days with 30C and driving set the cell temp well above 30C, and my car has not cooled the battery when not driving (not meaning the afterrun of fans etc shortly after a drive).
I have logged data for the battery temp during > 1 year. In the sun hot summerdays, the cell temp could be about 5C higher than ambient, thats in Sweden. I guess even hotter places could heat the battery more ( sun angle over the horison higher, hitting the car from a better angle.
It would reduce the degradation, but perhaps not very much compared to 50% charges.
If its possible (you perhaps can not use charged beforte the drive, if it can not be planned?) charge before the drive.
I changed job last year, but before I charged to 55%, the charging was set to commence about 03:00 to 04:00 depending on the season to reach 55% shortly before the drive to the work. At the end of the day, the car had 25-30% (summer), 15-25%(winter). It was enough for any non planned evening drive, to friends or to go to a workout session etc.
Even with the 55% SOC target, it never really stod with 55%. At work with about 40-45% for 8 hrs, at home with about 25-30%, and maybe 20-30% during the night after a evening drive. The average was about 35% during one year.
Im not sure for who this message is?
If using low SOC, the cell will get in balance quite quick and then stay balanced. I have had 4mV more or less any day during the two years I had the car (I have Scan my tesla with a screen in front of the steering wheel, so I see it daily.) Even after a long holiday trip with full charges and several superchargings to 70-80% in a row, when the car is back home I see 4mV at 55% more or less directly. (Teslas balancing target is 5mV so 4mV is in pair with, or better than a recently balanced battery.)
There is no risk of loosing range due to this as the 4.5% buffer below cover the imbalance.
If using low SOC with the cells “selfbalanced“ at low SOC, there might be slightly more to balance when charging full so tha 100% full charge might take a little longer than for example a car that is daily charged to 90%.
-On the other hand, after a year with the low SOC strategy, charging to 95% will give more range than other cars at 100%.
The researchers most often do the calendar aging tests for one of two years. There has been a lot of reasearch about the calendar aging, and as it seems it continues to follow the square root of time.
There are a few calendar agiong tests for three years, but there was no change in behaviour.
Tesla cars temselfs also continue to follow the curve.
Anyway, as calendar aging decreases quite fast (square root), if you manaeged to keep the degradation low for two or three years you already have made a big difference to the regular 70-90% SOC charging.
This is not a research study, nor is it only 8 cars. It was 8 cars that had charging data at the same ODO. There is at least 35 or so M3P 2021 using teslafi sending data. It was 8, after the evenings 100% charge that showed my range 495km, there is only 5 cars today with charging data at that ODO Reading.
This is not research, but there should be something to it when my car has much less degradation than the average similar car.
(also, in a swedish forum there now is several cars following my advice since one-two years…they have one thing in common: low degradation)
New cars range 507km, my has lost 12km, the average has lost 46km.
In the end it is up to anyone to make the choise of how to handle their car. The battery will hold together anyway, if just following Teslas advice So there is not an issue.
But if someone would like to reduce or minimize the degradation, following the results that science/research have given us would be a good idea.
Other than science with extensive research there is…..nothing but rumors and myths which in many cases are completely wrong.
Tesla does not say much, but I have references (quite old) from what tesla did say:
A Bit About Batteries | Tesla
I learned the basics of lithium batteries more than ten years ago. I did find the advices conflicting, sometimes strange, and also found that most peoples lithoum batteries died when they followed the ‘strange’ advice.
After reading quite some research I saw that there was a lot of forum rumors.
I try to inform about what the research has found, also I specially try to counteract the myths that clearly is not correct and maybe lures people to use a bad approach as they try to be nice to the battery.
When myths is used as advice, I step in and try to correct.
Theres people that doesnt care at all. Thats not a problem. If you do not care, there is no issue
A classic question is “My Tesla has high degradation, despite my effort to baby the battery at 80%”.
After learning how lithium batteries degrades its a quite easy approach, that does not need a lot of thinking, three simple points:
- Do not charge more than needed until the next charge (Include a personal range anxiety margin).
- Charge often (As smaller DoD reduce the degradation, and more important: reduce the needed charge level, se the point above).
- Charge as late as possible (reduces the calendar aging).
That’s it.
Some people like to either just know whats the best for the battery and some really like to make the degradation as low as possible, even if it gets awkward. I think they should be allowed to.
Going into details about how degradation works and the absolutely best way to threat the battery does lot necessarily mean that this is how we actually do. Knowledge is not heavy to carry.
[Edit]I would like to turn the question away from:
Many of the answers early in this thread is completely wrong. We know this from science.
Also, there is statements about Teslas advice that is completely wrong. Tesla never said that you “should” charge to 90%.
Several of the initial answers on OP question is clearly forum myths.
Non true statements should be corrected!
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First, this study seems to be based on generic auto cells, not Tesla's.
That's not the way that I'm reading it. I'm seeing only an 8% additional decrease over 15 years with battery aging still seeming to be the biggest factor.
But I think that the biggest thing that the report is saying is that the battery's going to last beyond 15 years and beyond, no matter what SoC you use. It even seems to be viable at 20+ years.
That tells me not to worry about it. SoC does not make a significant difference.
Definitely possible, although not sure if it's worth the effort to do it. I certainly do this with my PHEV because I'm adjusting the schedule every time I pull into the garage and I generally don't plug in until the night before I am going to drive it next. But I don't have the patience to micromanage the Tesla like this. Most I would do is not plug in until the day before I am going to drive it but that runs a risk of just outright forgetting to charge it. So even though it does charge by the next morning, it is only charging to 50%.
What does the heat pump do when it's 46°C outside? That happened once here and it was awful, but I can't really see what my heat pump is doing. The AC in my house was running (although not continuously) between midnight and 6 am at that time and the garage felt like a sauna in the afternoons and evenings. It was basically a 3-5 days of high temperatures > 40°C.
Now with regard to degradation being proportional to the "square root of time", is it actually the square root of time, or the square root of some function of previous degradation? For example, if you keep degradation incredibly low for 8 years (let's say you somehow keep degradation down to just 5% over 8 years), and then you switch to a new battery management strategy (or sell the car to someone else who isn't as careful at managing the battery), does the battery behave like an 8 year old battery (square root of time), or does it behave like any other battery that's degraded by 5% (square root of some function of previous degradation) that's being treated similarly?
Let it float starting at a level you are comfortable with charging, and dropping to ~20-25%. If you need to drive more urgently, stop at a nearby fast charger to increase SOC to what is needed for your trip. I charge to 80% because that is below the Tesla designated trip, and then recharge when needed. I wouldn't overthink it. You'll spend more time worrying about it than its worth.
beatle
Active Member
Surprised nobody has mentioned that a higher SoC results in a higher battery voltage, and more voltage means more power. I care about my battery, but I always charge to 90% so the car always has the most power available. Even if higher voltage is worse (and it's not) for the battery, I think it's a worthwhile tradeoff.
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