Tesla sets charge limit to 90%

[AAKEE]

It's pretty convincing, thanks @AAKEE. I have yet to see any evidence that refutes your claim.

Believe me, I have tried to find arguments that contradicts what I have learned from several years of reading research reports.

There is not.

There is some reports that find a slighly deviating result from [main stream].
In most cases this is due to faulty test setups that hides important facts, causing the researcher to draw faulty conclusions.
In some cases its possible to find the reason by reading carefully and compare with other reports, for example that the current in cyclic tests had been much higher than whats comparable to an EV normal use.

From the people that absolutely do not believe this research, I yet have to see even one statement that is backed with *any* credible source.

The research is quite clear and the researchers find more or less the same findings. There is a lot of research so for anyone to decide that these data is not true, its about the same thing like stating that the world is flat.

 

[DayTrippin]

I like to keep an open mind, but I'll follow the data and science. So far I have seen lots of scientific evidence advocating for the low SoC strategy to minimize degradation, while I haven't seen any evidence against it (at least not for battery degradation). But I agree that it's not for everyone.

This is why you want to go for the car with the greatest range if it is affordable for you if you are concerned about longevity. IF I start with a car with a 400 mile range, and at 55% SoC can easily go almost 200 mile without recharging, I barely will wear the battery. How often do you really need to go 200 miles except on a trip.

The other key component of this is AVERAGE SoC. So if you keep it 50 most of the time, charge for your day (if needed to 80%) just before you go, it will hardly have any impact on the average SoC (let's call it aSoC). So think of using just in time charging to keep your aSoC as low as possible. In the term of a year, charging to 80% for just a few hours and the depleting it over another few hours, is barely a blip on the number of hours in a year when calculating your aSoC. It becomes ever more critical in hot weather to keep the aSoC low as the heat, combined with high SoC, accelerates degradation more than almost anything else I've seen.

All I can say is it has worked now great for me for 3 cars and I'll be doing it to my 4th. The person who bought my Y has been following this approach religiously since I taught him and he has only 3% degradation in 60k miles, coming up on 2 years for the car that lived its entire life in a hot Florida and Texas climate with a lot of supercharger use. Again only supercharging as high as he needed and deep in the lower charge levels where the battery can more easily tolerate the higher rate of charge. Basically he would charge from about 15/20% to 50-60% and be on his way. At home he kept his charge level at 50%. He has a 360 mile round trip commute 2-3 times a week. The Y has ran flawlessly and eats up tires faster than it does kilowatts.

 

[702sunk]

This is a research/test which used actual Model S 18650, from a Tesla that was used for 6 months since new. Report from 2017. so maybe a 2015 or 2016.
I have had this report for a while but if I remember it right, I havent used this as reference before.
Remember, this is not a question of finding one specific report showing something, it is the sum of reading more than 100 research reports, and disregarding a few of them. The rest, still more than hundred, builds the case.




Note, that the calendar aging is highest at about 80%, a thing I have been writing about for quite long time.
Also note that 50% and below have significantly lower calendar aging.

For warm climates, it will be a considerable difference having the cells at 55% or below.
These numbers match the other reserach quite well, I calculated that the step1 and step2 cyclic aging must have taken about half a year, so these numbers is for month 6-12 in the cars age.
View attachment 934226
Tesla Model S18650 test

This is the cyclic test of the same cells, confirms that the degradation per cycle for full cycle (100-0%) is in pair with virtually all the other research.
View attachment 934228

As this test only had four datapoints for calendar aging 20-50-80-100, it will hide the true form of the graph.
Using this graph that do not hide the step that is caused by the central graphite peak as it use 16 SOC points we easily can se that it is benifical to stay below 55% - Actually, reading that report show us that the real step is at 57-58% on a new NCA cell. Tesla hides 2% SOC on model 3/Y at 55%(part of the buffer is hidden there) så charging to 55% keep us on the right side of 57-58%
View attachment 934233

Great info. Still a newbie to tesla world, but what is considered SOC? Is it a certain duration while the car is not in use? If it is, how long is considered SOC? My tesla is set for scheduled to be charged at 75% before the departure typically around 8am and I end up using about 25% ~30% each day. I think I’m doing ok??

 

[Iron]

SOC = state of charge. This is the percentage of charge that the battery has at any given moment

 

[Art84]

My tesla is set for scheduled to be charged at 75% before the departure typically around 8am and I end up using about 25% ~30% each day. I think I’m doing ok??

Yes, you are absolutely fine. But based on the research mentioned above in this thread, if you really care about the degradation of the battery, you can reduce the SOC limit to 65-70% and you ll return home with about 30-40%. So this is around the sweet spot where to keep the battery charge level.

 

[AAKEE]

Yes, you are absolutely fine. But based on the research mentioned above in this thread, if you really care about the degradation of the battery, you can reduce the SOC limit to 65-70% and you ll return home with about 30-40%. So this is around the sweet spot where to keep the battery charge level.

He should stay at or below 55%, as it is a car with the PAnasonic NCA. The steep step in degradation is at ca 57% true SOC, which transfers to 55% on screen SOC.
60% to 100% cause about the same degradation.

 

[Tom Sagrak]

I'm driving weekdays up to 20-30km a day and do not see any reason to plug into my Wall connector every day. Come on, I'm too lazy to fiddle with the cable to keep the battery in extra optimal contidion. Just charging it when it drops below 35% and going up to 70% or 80% if weekend trip is about to start.

 

[cpaull]

I'm driving weekdays up to 20-30km a day and do not see any reason to plug into my Wall connector every day. Come on, I'm too lazy to fiddle with the cable to keep the battery in extra optimal contidion. Just charging it when it drops below 35% and going up to 70% or 80% if weekend trip is about to start.

I believe that @AAKEE is just making the point that <55% will minimize battery degradation. It may not be the best overall for your usage/convenience, or many other factors. Your battery may degrade slightly faster, but as @Art84 says, "Yes, you are absolutely fine."

FWIW: I typically charge to 80% then re-charge when it gets below 50%, and my 85KWh battery still charges to just under 200 miles (rated) at 80%. Although I did just today lower my max to 70% based on this data. For me this is the optimum point when considering all factors (usage/convenience/degradation/etc.).

 

[HMHM]

I have always charger to 90% for the eight years I have owned my model s.

That sounds amazing. I sense that you are quite satisfied with this routine, and the performance of your battery during the past eight years. What is the level of your MS battery's degradation after eight years?

 

[DayTrippin]

Keep in mind Tesla doesn't care how long your battery lasts, as it makes it past the warranty period before degradation is over 30%. Think about how much even 25% degradation will impact you. That is still within spec. That would be losing 1/4 of your range.

Degradation also impacts your performance. The battery and motors work together. It could be the ability of the battery to flow a certain amount of current to feed your hungry EV motors. How do you think they are going to react if they needed close to 100% of your battery's power to get you to your claimed 3.1 or 4.2 second 0-60 time?

Are you going to enjoy the acceleration as much if it was whacked 10%? 20%? 29%? As that all would be in spec according to the battery warranty. It has been a while since I read it, but my interpretation is you could have 20% range loss in the first year, and 1% thereafter, and as long as it hasn't dropped below 30% degradation by the end of the warranty, Tesla thinks you are still good. Now I could make a good argument after year 1 and a 20% loss is abnormal but Tesla won't immediately roll over and drop a $25k battery pack in my car. They'll look for any out in how I maintained the battery, used the car, etc. to deny a claim for as long as they can.

It is your money, your car, your usage and up to you to figure out what makes the most sense. Maybe throw a little common sense in there while figuring this out. There is almost no downside to what I've suggested or @AAKEE either on how to get your non-LFP pack to last longer. Why charge to 90% every day if you never use more than 10-20% of the capacity on a daily basis? While not a perfect analogy, it might resonate with some. Do you run your ICE motor almost to redline every day just because you can? My redline is 9k so as long as I don't exceed it, or just go to 8k, all is great. Or do you shift a bit sooner because you know sustained high revs are bad for a motor and will increase wear over time? Dropping peak charge from 100 to 90 is good, get down to 50% is best based on a lot of research.

Here is a nice, simple to read article that might help but doesn't talk explicitly about what charge level is best. AAKEE has shown enough of that I hope everyone has caught on by now.

Everything You Need to Know About Lithium Battery Charging Cycles

how to charge a lithium battery? Everything you need to know about charging lithium batteries can be founded here, help your lithium battery charge quicker, last longer.

au.renogy.com

 

[BB82]

Not exactly sure why i do it this way but charge to 80% at 32amps. Then every 2 weeks or so I will charge to 90% 1x. Usually run the battery to 30% or so then charge again. Really don’t think it makes much difference

 

[AAKEE]

Here is a nice, simple to read article that might help but doesn't talk explicitly about what charge level is best. AAKEE has shown enough of that I hope everyone has caught on by now.

Everything You Need to Know About Lithium Battery Charging Cycles

how to charge a lithium battery? Everything you need to know about charging lithium batteries can be founded here, help your lithium battery charge quicker, last longer.

au.renogy.com

I started reading the article and it seems that they mix Lithium Polymer
With lithum ion batteries.
Its not the same chemistry, at all ( yes, they borh contain lithium but…).

They also mix cycles with Full Cycles equivalent (FCE), and they missed the part that shallow cycles will increase the number of FCE cycles these batteries can do.

At this point after finding more faults then rights I did not read any further. I suggest finding a better source for this.
Batteryuniversity.com contains some not correct parts, and also use some part of bad research report but in general most part of their information is sort of ok.

 

[AAKEE]

Not exactly sure why i do it this way but charge to 80% at 32amps. Then every 2 weeks or so I will charge to 90% 1x. Usually run the battery to 30% or so then charge again. Really don’t think it makes much difference

In the forums i write and read at, and also collegues and friends, there is now a considerable number of cars that have charged to 50-55 (or 60% for NMC cells) since new, and its very easy to se that the low SOC makes an noticable difference in degradation. There is no exemple of a car kept at low SOC that has high degradation. There even is no one that is on the average line. They all do way better than this.

A BMS Calibration shouldnt change anything if the BMS was on track to begin with. Also, a increased range from a BMS calibration does not mean that the battery increased the capacity. Its displayed range only, and the BMS that shows a higher number.

 

[Art84]

I am appreciative @AAKEE for sharing the knowledge about research he made and keeping this topic answering the questions.
Even I always was the guy who is like "set to 80% and forget about it", reduced my daily charge limit to 70%. Will see how comfortable I ll be to go to 60%

 

[Iron]

In the forums i write and read at, and also collegues and friends, there is now a considerable number of cars that have charged to 50-55 (or 60% for NMC cells) since new, and its very easy to se that the low SOC makes an noticable difference in degradation. There is no exemple of a car kept at low SOC that has high degradation. There even is no one that is on the average line. They all do way better than this.

A BMS Calibration shouldnt change anything if the BMS was on track to begin with. Also, a increased range from a BMS calibration does not mean that the battery increased the capacity. Its displayed range only, and the BMS that shows a higher number.

Thanks for the info, AAKEE. I've begun charging to 60% using scheduled departure, so all charging completes right before I leave in the morning. By the time I get to work, I'm at 52%, where it sits all day till Ieave. By the time I get home, I'm at 44%, where it sits all night till it repeats again in the morning.

I found this info on BMS. Think I'll incorporate it as well.

Tesla battery management system (BMS) calibration

Tesla battery management system (BMS) calibration instructions

tesla-info.com

How to improve the battery management calibration​

As said, the BMS needs a number of stable readings at different states of charge. To get a stable reading, the car needs to be left in it's sleep state for several hours. The following steps are fairly simple and are not required to be done that often to help the BMS achieve a good level of calibration.

• Leave the car overnight and/or in the day occassionally without sentry mode enabled allowing the car to deep sleep for several hours.
• Do not charge the car every night. Leaving the car at different states of charge, across a broard range, helps provide a spread of readings. Even once a month, at a SoC below 50% can help.
• Turning off 3rd party apps that keep the car awake, and don't query the car with the Tesla app unless necessary while doing either of the above.

The goal is to build up a number of occasions where the car totally asleep for 4-6 hours and across a variety of charge levels.

Over time the car should recalibrate itself using these reading and should correct any under reading of the available range plus you are giving the battery time to sort itself out and the various battery groups to stabilise between themselves.

 

[CaseyL]

Thanks for the info, AAKEE. I've begun charging to 60% using scheduled departure, so all charging completes right before I leave in the morning. By the time I get to work, I'm at 52%, where it sits all day till Ieave. By the time I get home, I'm at 44%, where it sits all night till it repeats again in the morning.

My habit is similar, but averages about 10% lower than yours.

I charge @4:00 am to 50%. I arrive at work with about 42%, and the car sits in the hot Florida sun. When I get home I have about 34%, until the recharge at 4:00 am.

 

[HMHM]

Well, yes, but don't drive yourself crazy with it. It doesn't matter if you skip a few days either.

They are trying to keep things simple with one recommendation that has to cover a variety of purposes. So it's like the K.I.S.S. principle.

There was some pervasive myth and misinformation about electric cars quite a while ago that if they were left plugged in, they would overcharge and explode. Tesla was having to dispel that myth, to let people know that it's FINE to keep your car plugged in as often as you want for as long as you want, so you don't need to keep it unplugged on purpose.

Also, they're trying to build good habits for using the car. They don't want people trying to intentionally run it low before charging, and then some travel need comes up, and they don't have enough range, and people are angry at the stupid EV that ruined their plans. So they're trying to keep that reminder to plug in often, so people do have enough range when they need it.

They are trying to keep things simple with one recommendation that has to cover a variety of purposes. So it's like the K.I.S.S. principle.

I own a 2023 MYLR7. Since my daily commute is 20 mi RT, I have been told by family friends (Tesla owners) and folks on this forum that I can limit my DoD to 12 or 15%. So, I'm setting my new charging limit to 65% and plugging in each evening with around 50 to 55% SOC. Would this be a prudent strategy to enhance the cycle life of my battery pack and dramatically slowdown its degradation?

 

[E90alex]

I own a 2023 MYLR7. Since my daily commute is 20 mi RT, I have been told by family friends (Tesla owners) and folks on this forum that I can limit my DoD to 12 or 15%. So, I'm setting my new charging limit to 65% and plugging in each evening with around 50 to 55% SOC. Would this be a prudent strategy to enhance the cycle life of my battery pack and dramatically slowdown its degradation?

If you’re using only 10-15% then I would lower it to even 50-55% charge limit whilst plugging in everyday.

 

[HMHM]

If you’re using only 10-15% then I would lower it to even 50-55% charge limit whilst plugging in everyday.

My daily commute is only 20mi RT. I'm not sure whether to set the DoD limits at 60/40 or 70/50, if I was driving a total of 30 to 40mi/day, 2-3 times a week. These conditions are close to the real life daily mileage variations due to routine chores, dinning/social, and recreational activities. I'm concerned, due to battery degradation, about the long-term health of my battery. So, at the end of the day, is the SoC at 40% better or 50%?

 

[E90alex]

My daily commute is only 20mi RT. I'm not sure whether to set the DoD limits at 60/40 or 70/50, if I was driving a total of 30 to 40mi/day, 2-3 times a week. These conditions are close to the real life daily mileage variations due to routine chores, dinning/social, and recreational activities. I'm concerned, due to battery degradation, about the long-term health of my battery. So, at the end of the day, is the SoC at 40% better or 50%?

Whatever is the lowest you can manage or be comfortable with is better in terms of battery degradation. If you start with 60% and never end the day with less than 40% after commuting and everything else you need to do, there’s no reason you can’t do 50/30 instead. Even if you forget to plug in one day and use another 20% the next day, you would still be at 10% which is totally fine for the battery. As long as you can make it home and plug in before it’s dead, that’s all that matters.

I understand some people like to have some buffer at the end of the day “just in case” they suddenly need to leave town or something and that’s fine. So if you feel more comfortable at 60/40 or even 70/50 instead of 50/30 then by all means charge it higher.

Personally as long as there’s enough charge left to get to a supercharger if needed, there’s not much to worry about. I end the day with 35-38% and with my Model 3 LR that’s enough to get me from Seattle area almost down to Portland or up to Canada. That’s way farther than I’ll ever need to go at the drop of a hat, not to mention there’s going to be several superchargers along the way in any direction.