Is 100% charge on MYLR once a month good for extended battery life?

[AAKEE]

Aakee:

Two questions:

1) Am I to take away from this that battery temperature is also important? I see a battery at 25C has significant less calendar aging than one at 50% (other things being equal).

Calendar aging can be described as = Time x SOC x Temperature.

Of course the rate is not completely proportional to the SOC, but to understand how it works it might be good.

Reduce time or
Reduce temperature or
Reduce SOC

And the calendar aging will reduce.

The temperature dependant part can be seen as depending on the Arrhenius equation.

2) Looking at the charts you post, they seem contradictory. The first shows quite a bit of aging over 80%, a notable increase over ~95%. The second contradicts this, showing a marked dip at 80% and improveing again as SoC increases. Which are we to use as "bottom line"?

For common understanding, use the one with about the same degradation above 60% for NCA. Its a good way to see it.

For the difference between these two charts, almost any chart shows signs of that the calendar aging is less at 100% than at 75-90% if the temperature is not to high.

For shorter time, like the 2.1 month line, all three chemistries show that behaviour. I guess its pissible to see that?
As we do not in general leave the cars for
Months at 100% SOC, we can guess that the short term behaviour could be more like that at 100%.

I usually use the pictures with “worse at 80%” to make it very clear that 100% is not very very bad, and that 80% is not very very good.

There is more than one example of seeing kower degradation at 100%.

This is Panasonic 18650 NCA cells.

The takeaway is that there is no babying part keeping the battery at 80% or so.
To reduce the calendar aging, stay at 55% or lower. (most people can not affect the ambient temperature).

And, that the urgency to drive asap after a full charge is not really true.

For the common understanding, I’d say that the calendar aging is virtually the same at 70-100%, unless in very high ambient temperatures. In that case it is slightly higher at high SOC, but not by far.

 

[AAKEE]

Many people seem to think that the batteries is damaged by 0% SOC and 100% SOC.

In reality, lithium batteries can be charged
well above the 100% SOC mark.

100% is 4.20V/cell for many chemistries but it is possible to charge them to 4.4V. The
life will not be that many cycles but it can be done.
The battery manufacturers set a max level ( 100% definition, that is safe for the battery in question. When reducing the max voltage from 4.4 to 4.2V this is done to give the battery a descent life with an acceptable number of cycles and calendar aging.
The 100% level set by the manufacturer is of course on a safe level. If the cells would break when used at 100%, the manufacturer would get a lot of warranty exchanges.

The same with the 0% level. 0% is not completely empty but the safe discharge level, set as a minimum discharge level.

The specification might say 500 or 1000
Cycles 100-0% and research tests often
confirm this.

The most left part of the picture is 100% to 0%. Some 625 full Cycles or about 250.000km/155.000 miles. (400km per Full Charge until it stops)
Doing 100% until the car stops well
Below 0% on the screen, will still give us quite many miles to drive.
Middle is about 90% to 0%
Right is about 80% to 0%

 

[dafish]

Thanks again Aakee.

So the universal truths regarding aging appear to be:

1) Any test will show staying below 55% SOC reduces calendar aging relative to higher SoC.
2) While sometime outside our control, higher stored temp always increases calendar aging.
3) Time spent at very high SoC matters, but this should be viewed in a "months" at SoC perspective not minutes.

FWIW, I buy new cars with the options I want and keep them for 10 years. For me taking care of things has a clear ROI. To say nothing of having a better product for the next owner.

 

[Iron]

Is 100% charge on MYLR once a month good for extended battery life?​

Im gonna try to answer the question as posed.

It's not good for extended battery life but it may be good for BMS calibration and cell balancing. This will allow the car to give you a more accurate reading of SOC and remaining miles, among other things. It may be even more prudent to do, if maintaining a narrow SOC with the goal of battery preservation.

I would probably do it every three months or so, letting the car sleep for three hours after charging, then driving it to lower the SOC.

 

[agmonaco]

Great exchange.... Thank you!

 

[Iron]

The Tesla community has a problem or two:

-Not reading the manual but using not correct info from forum/facebook and taking these as true facts. (For example, saying that Tesla recommends 80 or 90% as the daily charge to a LR/P. The manual on all LR/P says ”to under 90%” which per definition is *any* setting below 90%.

@Akee, they actually do say it though. Right on the app! If you slide the charge percentage on the app to anything over 90, it says..
Charge Tip
• 90% recommended for daily driving

Slide back to 90 or less and the message disappears. Not sure if this is a new phenomenon. Haven't charged over 60% in many months.

 

[AAKEE]

@Akee, they actually do say it though. Right on the app! If you slide the charge percentage on the app to anything over 90, it says..
Charge Tip
• 90% recommended for daily driving

Slide back to 90 or less and the message disappears. Not sure if this is a new phenomenon. Haven't charged over 60% in many months.

I’ve seen that in posts. Its a recent change in the app but not for my plaid.

My way of interpret that it is that it is supposed to make the ”stay below 90% for daily charging” more clear.
I’m positive that the do not mean that they recommend 90% over lower charge settings. The problably ment 90% or less.
(As in ”below 90% innthe manual).

The manual has not changed, and is the same for all LR/P cars.

In general, I would recommend thrusting the manual over small notes in the app, even if they should not give contradicting advices.

Edit, updated the app and got the same.
Only visible above 90% (from 91% and up) so I rest my case with the statement that it is supposed to keep people at 90% and below for daily.
If they really recommended 90% all over, we would se that at 50-89 also.

 

[dhrivnak]

Ok I was at the Tesla Service Center and with my 2023 MYLR manufactured in Austin. The service rep told me it was a good idea to charge to 100% once a month to extend battery life. I have also read and seen videos this is necessary to do once in a while to balance battery. And drain battery to 10% also once in a while. I have not seen any posts here that address this. Thanks for responding. I have the 2170 batteries. I normally only charge to 70%. The manual gives no guidance about this.

My experience gained over 13 years of owning a Tesla, and my Model 3 now at 110,000 miles after over 5 years is yes. But maybe not monthly as 4-6 times a years is plenty. I charge to 90% regularly and 100% 4-8 times a year when planning on a long trip. Charging to 100% allows for better cell balancing and I know on the Roadster you needed to be above an 83% charge for balancing can occur. Without proper balancing you will be limited in rage to the weakest brick. Attached is my 90% charge graph showing I still have 95% of new after 110,000 miles.

 

[AAKEE]

My M3P refresh with the panasonic 82kWh batt, always was at 4mV normally. That despite long periods up to 4-6 weeks with 55% target only.
Drive a lot and have longer trips about once a month or twice, so I havent had 55% for more than 6 weeks I think. But no increase in the imbalance from that.

 

[Iron]

Only visible above 90% (from 91% and up) so I rest my case with the statement that it is supposed to keep people at 90% and below for daily.
If they really recommended 90% all over, we would se that at 50-89 also.

Agreed. I took it as 90% or less also. If dropping to 50% were an issue, the message would have reappeared.

I believe the 90% recommendation is to provide good range. I'm sure they don't want those limiting charge percentage to hurt their long range reputation. You know how perception can be. Basically, we are operating the vehicle somewhat like a Nissan Leaf, even thought it has way more capability.

I only noticed it because last night I decided to charge to 90% after midnight, so it would charge with enough time to sleep for 3 hours, before I left for work. This is purely for calibration/cell balancing purposes. Was going to do 100% but the message dissuaded me. I'll be back to 60% tonight.

Attached is my 90% charge graph showing I still have 95% of new after 110,000 miles.

Interesting that for the 6 months in 2019 you charged to 80%, you experienced the range loss. Was anything else different about your routine?

 

[AlanSubie4Life]

Attached is my 90% charge graph showing I still have 95% of new after 110,000 miles.

~95% of original 310 miles. (297 miles)

69.2kWh, 234Wh/rmi for LR RWD * 297rmi - about 89% of original battery capacity. (More relevant than original stated range if you are concerned about how far you can go…with the caveat that I don’t know whether they just increased degradation threshold or unlocked some of the battery (EPA data strongly suggest they did not) originally when going from 310 to 325.)

 

[Stack24]

I'm picking up my wife's car tomorrow and all this information has been helpful.

If she is a person that probably drives 25 miles or so a day, mainly errands and picking up the kids, would it be best to let the charge get down lower and then charge it up at the end of the week? Or just set a charge limit like 55-60% and do it daily?

Thank you in advance.

 

[AlanSubie4Life]

I'm picking up my wife's car tomorrow and all this information has been helpful.

If she is a person that probably drives 25 miles or so a day, mainly errands and picking up the kids, would it be best to let the charge get down lower and then charge it up at the end of the week? Or just set a charge limit like 55-60% and do it daily?

Thank you in advance.

Charge daily to what you need plus comfortable margin. It reduces cycle depth which is good (get more full cycle equivalents with shallow cycle depth). It’s also good advice directly from Tesla.

It’s also good to be in the habit of always plugging in when you park, so you can always be sure you will wake up with a charged car (also insures no massive unnecessary electric charges in case of TOU billing).

It’s easy to forget to do if you’re not in the habit. No one wants to be running out to the garage to plug in the car. That would be very inconvenient; no one does that!!!

If you need to boost the charge level you can (in theory) do that from the app, as needed. Of course I can’t because it’s nearly impossible to wake my car up from sleeping, lol. But at least I’ll get my 50% or higher. If I need higher I usually have to do the walk of shame and humiliation to the garage to adjust the charge level manually (Teslas, at least 2018 vintage, enjoy humiliating their owners, 1) by not allowing the app to connect and wake the car when sleeping and 2) by not opening the doors when you’re right there with your phone).

 

[AAKEE]

I'm picking up my wife's car tomorrow and all this information has been helpful.

If she is a person that probably drives 25 miles or so a day, mainly errands and picking up the kids, would it be best to let the charge get down lower and then charge it up at the end of the week? Or just set a charge limit like 55-60% and do it daily?

Thank you in advance.

@AlanSubie4Life has probably already nailed it.

Your wife’s car, what model is it (will it be)?

-If it is a LR/P, 55% or lower is good.
-If it is a RWD, 70% or lower is good.

To start with, the battery will hold up just buy following the very simple Tesla advices.

If only driving 25 miles a day, it doesnt seem like there is a big need to ”save” the battery from degradation?

If you still would like to reduce degradation, charge as low as possible, charge often and charge late (shortly before the drive).

 

[Stack24]

Charge daily to what you need plus comfortable margin. It reduces cycle depth which is good (get more full cycle equivalents with shallow cycle depth). It’s also good advice directly from Tesla.

It’s also good to be in the habit of always plugging in when you park, so you can always be sure you will wake up with a charged car (also insures no massive unnecessary electric charges in case of TOU billing).

It’s easy to forget to do if you’re not in the habit. No one wants to be running out to the garage to plug in the car. That would be very inconvenient; no one does that!!!

If you need to boost the charge level you can (in theory) do that from the app, as needed. Of course I can’t because it’s nearly impossible to wake my car up from sleeping, lol. But at least I’ll get my 50% or higher. If I need higher I usually have to do the walk of shame and humiliation to the garage to adjust the charge level manually (Teslas, at least 2018 vintage, enjoy humiliating their owners, 1) by not allowing the app to connect and wake the car when sleeping and 2) by not opening the doors when you’re right there with your phone).

@AlanSubie4Life has probably already nailed it.

Your wife’s car, what model is it (will it be)?

-If it is a LR/P, 55% or lower is good.
-If it is a RWD, 70% or lower is good.

To start with, the battery will hold up just buy following the very simple Tesla advices.

If only driving 25 miles a day, it doesnt seem like there is a big need to ”save” the battery from degradation?

If you still would like to reduce degradation, charge as low as possible, charge often and charge late (shortly before the drive).

Thank you for all the information and help.

We are getting the Performance model. I think on a busy day she might hit 50 miles. But majority just city driving around our area.

 

[AlanSubie4Life]

Thank you for all the information and help.

We are getting the Performance model. I think on a busy day she might hit 50 miles. But majority just city driving around our area.

The other consideration is the feature lockout limitation. I like to ensure I stay comfortably above 20% so I can use all the features (Sentry, etc.). That limitation is a bit annoying actually; I’d prefer 10%, but Tesla does not want people to get stuck!

But anyway usually 55% charging every day stays comfortably above 20% for me. When it is not (rare) I try to remember to increase charge level in advance (prior day).

Anyway you’ll need to account for that 20% level in your charge level decision-making process.

I have TOU (time of use) billing, so I can’t charge during the day between errands or whatever. Those who can charge whenever may have less of an issue depending on the scenario.

 

[AAKEE]

Thank you for all the information and help.

We are getting the Performance model. I think on a busy day she might hit 50 miles. But majority just city driving around our area.

One thing to remmber is that low SOC will limit the power by a little.
If your wife experience that the car feels sluggish or slow, you might need to increase the charge limit. (55% might even put here at below 300kW on the throttle).

Just kidding, I wouldnt think that will be an issue.

Stay at or below 55% when the idea is to refuve degradation.
If / When power is needed, charge to 90% and if possible charge shortly before the drive with max available charging power to heat the battery. This will give extra power.
(Charging late also keeps calendar aging low).

 

[Iron]

If she is a person that probably drives 25 miles or so a day, mainly errands and picking up the kids, would it be best to let the charge get down lower and then charge it up at the end of the week? Or just set a charge limit like 55-60% and do it daily?

The latter. You will control whether or not it charges via the app. I like to say PLUG IN DAILY, because being plugged in doesn't necessarily mean charging, but charging always means being plugged in.

If you haven't contacted the electric company yet, do so and get a time of use rate. Then you will figure out the best charge times. Also it's best to charge close to needing to drive so you don't the car sitting with a high SOC. Mine completes charging each morning roughly 20 mins before I leave for my commute.

Having everything automated helps to keep things optimal. You just can't automate plugging in. I leave my charging cable unfurled and the end hangs on a hook a few feet away from the charge port.

 

[dhrivnak]

~95% of original 310 miles. (297 miles)

69.2kWh, 234Wh/rmi for LR RWD * 297rmi - about 89% of original battery capacity. (More relevant than original stated range if you are concerned about how far you can go…with the caveat that I don’t know whether they just increased degradation threshold or unlocked some of the battery (EPA data strongly suggest they did not) originally when going from 310 to 325.)

Right or wrong I never saw more than 315 miles even after the "unlock" and 309 when new. I am using the 310 number as that was the starting range of my car and I can often get close to rated range on most trips.

 

[AAKEE]

Right or wrong I never saw more than 315 miles even after the "unlock" and 309 when new. I am using the 310 number as that was the starting range of my car and I can often get close to rated range on most trips.

The actual driving range depends on so much that is is not really connected to the EPA Range.
I did 319 miles with my M3P last year after > 1 1/2 year and 40K km, that had 315miles new range. It would be pissible to do 400 miles if driving slow enough.

We should compare the actual capacity to the new cars capacity.