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What should my ideal charge percentage be?

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So I have a few data points to share from an older Tesla. First of all calendar aging seems to be discounted by this theory. It basically says a well made Tesla battery before they started making the 3 and y battery’s will not be subject to calendar aging. Here is why, Tesla had their brand on the line in 2015 and there are numerous sources that will say the battery quality was the best that year. Don’t believe me? My car is 7 years old and has .04 degradation. Also I should say the mileage is the key factor per a Tessie representative. They said the battery life/ specifically degradation is based on recharging cycles. Therefore, the old owner of this car told me he did 60% a lot, therefore I know capacity charging is the most important element in degradation. All hail to 30-60% range charging ! PS this car was made in 11/2015 and has 1% degradation
 

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So I have a few data points to share from an older Tesla. First of all calendar aging seems to be discounted by this theory. It basically says a well made Tesla battery before they started making the 3 and y battery’s will not be subject to calendar aging. Here is why, Tesla had their brand on the line in 2015 and there are numerous sources that will say the battery quality was the best that year. Don’t believe me? My car is 7 years old and has .04 degradation. Also I should say the mileage is the key factor per a Tessie representative. They said the battery life/ specifically degradation is based on recharging cycles. Therefore, the old owner of this car told me he did 60% a lot, therefore I know capacity charging is the most important element in degradation. All hail to 30-60% range charging ! PS this car was made in 11/2015 and has 1% degradation
Well, with current technology there is no way to not have calendar aging, as we use the car with temperatures where calandar aging is a factor.
If you have used your car with 60-30% you did reduce the calendar aging by 50% in reference to 80%.
Some of the research for calendar agibg have been performed on the very same Panasonic NCA-cells or very similar to the cells Tesla use. They still suffer from calendar aging.
I do not know the climate where you live (Ohio?) but even in a cold climate with low SOC there is calendar aging.
If Tessie show you 0.4% after 7 years I guess this is because the BMS is a bit off track about your real battery capacity.
It is said here on TMC that charging to 55-60% can fool the BMS. I charge to 55% and had full range for 1 1/2 years, then after a drive down to -2% SOC, the BMS adjusted (and got as off on the low side as it was on the high side before :rolleyes:).

I would guess that if you did a 100-0% drive you would find that the battery capacity has reduced more than it looks like now…(not ment to take the joy from you seeing a low degradation right now).
My calc from Panasonic NCA 18650 and slightly colder climate (I guess?) would out you at about 4% calendar aging after 7 years.
 
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Well, with current technology there is no way to not have calendar aging, as we use the car with temperatures where calandar aging is a factor.
If you have used your car with 60-30% you did reduce the calendar aging by 50% in reference to 80%.
Some of the research for calendar agibg have been performed on the very same Panasonic NCA-cells or very similar to the cells Tesla use. They still suffer from calendar aging.
I do not know the climate where you live (Ohio?) but even in a cold climate with low SOC there is calendar aging.
If Tessie show you 0.4% after 7 years I guess this is because the BMS is a bit off track about your real battery capacity.
It is said here on TMC that charging to 55-60% can fool the BMS. I charge to 55% and had full range for 1 1/2 years, then after a drive down to -2% SOC, the BMS adjusted (and got as off on the low side as it was on the high side before :rolleyes:).

I would guess that if you did a 100-0% drive you would find that the battery capacity has reduced more than it looks like now…(not ment to take the joy from you seeing a low degradation right now).
My calc from Panasonic NCA 18650 and slightly colder climate (I guess?) would out you at about 4% calendar aging after 7 years.
My question is this, doesn’t Tessie base their degradation calculation on the max charge of the battery? So if that is true, and if my car charges to 265 miles and 265 miles was the max charge when new where is the degradation? Do you think the bms calculation for max miles has changed since new or is Tesla playing games to make the battery look like it hasn’t degraded?
 
So I have a few data points to share from an older Tesla. First of all calendar aging seems to be discounted by this theory. It basically says a well made Tesla battery before they started making the 3 and y battery’s will not be subject to calendar aging. Here is why, Tesla had their brand on the line in 2015 and there are numerous sources that will say the battery quality was the best that year. Don’t believe me? My car is 7 years old and has .04 degradation. Also I should say the mileage is the key factor per a Tessie representative. They said the battery life/ specifically degradation is based on recharging cycles. Therefore, the old owner of this car told me he did 60% a lot, therefore I know capacity charging is the most important element in degradation. All hail to 30-60% range charging ! PS this car was made in 11/2015 and has 1% degradation
Yes, the chemistry Tesla used on the 85 kWh Model S / X is much more resistant to calendar life degradation than the chemistry used on the Model 3 and Y. But it can't Supercharge as fast. Now, 1% seems unbelievable for 7 years, but anything less than 10% would not be abnormal, where the Model 3, 10% is pretty typical for 2-4 years.
 
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Most people do not drive not that much in hours each day. An average car is not used for 20hours or so each year.
While the researchers in most cases divide the degradation into calendar aging and cyclic aging, calendar aging happens even if the car is used (because time goes by even if the car is driven, maybe except for the Plaid ;) ) Some researchers do present calendar aging as a part of the cyclic aging test.
Count the calendar aging, as it happens anytime is the easiest way, and it is also correct.
If you like to see it the other way, your car probably is not on the road for ~20h each day (or more) so you still have 83% or more of the calendar aging.

Well, its also applicable to all other.
(The battery resesrchers use the same viewpoint as I present here.)

Your statement is wrong.


I try to help with facts found and the feeling I get is not as you wrote above.

I try to kill the myths about batteries, and there is seldom that much worries or protests. I guess the ones protecting the myths is the ones that have ”non happy posts” ( I do not mean you :) )

I think you're reaching here a bit: the evidence you're portraying shows the car is sitting for months at a time. Which is vastly different than being used daily.

Let me provide you with an example: I used to have a gas lawnmower which we used from May to September. After September, it'd be too cold and grass wouldn't grow and become dormant, so the lawnmower would not get utilized. So we would add a fuel stabilizer to the gas that we would store.

However, we didn't need to add the gas stabilizer during May to September, because we kept using the gas on a regular/weekly basis.

The same deal with battery would apply, no? If the battery is being used daily, then are you sure that what you're providing is still applicable?
 
LOL no believe it or not I asked them because of this thread and was just curious. I did notice when I charged to 90% when I got the car it showed a range of 353 miles and now it shows 319 miles but the range it shows really doesn’t mean anything.

Maryland can get hot in July/August and today it is unseasonably cold at 32 degrees Fahrenheit.

Wait until next spring/summer and you'll notice that some of your miles magically come back.

I've had several Teslas now and my range drops in winter and then gets back up in summer. LOL.

I wouldn't be too worried. As you said, that's what the warranty is for.
 
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I think you're reaching here a bit: the evidence you're portraying shows the car is sitting for months at a time. Which is vastly different than being used daily.
This has been covered multiple times in ’these’ threads.

Calendar aging happens even if the battery is in use.
The average car is driven 12k km a year (in Sweden). Thats 32 km a day. Lets call that one our of driving.
Charging this amount (6kwh) is 0.5-2hours for the most people. The rest of the day (some 85%) the car is at rest, including the battery.

So, calendar aging happens some 8700 hours of 8700 hours each year.
Of these 8700 hours the battery is at rest for about 85% of the time.

The researchers seem to have the same idea as I do (Actually I did get it from reading a lot of research reports ;)

As it seems, my car is mote or less spot on on the track for the calculation for calendar aging performed this way.

Cyclic aging is wuite small for most peoples cars so we can almost excluse it, or add 0.5-1% annually to the calendar aging.
 
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I think you're reaching here a bit: the evidence you're portraying shows the car is sitting for months at a time. Which is vastly different than being used daily.

Let me provide you with an example: I used to have a gas lawnmower which we used from May to September. After September, it'd be too cold and grass wouldn't grow and become dormant, so the lawnmower would not get utilized. So we would add a fuel stabilizer to the gas that we would store.

However, we didn't need to add the gas stabilizer during May to September, because we kept using the gas on a regular/weekly basis.

The same deal with battery would apply, no? If the battery is being used daily, then are you sure that what you're providing is still applicable?
Nope. The proper analogy would be that your gas tank shrinks, and the more gas is in it at any given time, the faster it shrinks. So irrespective of how often you're using the lawnmower, if it's almost always topped off to 100%, it's going to shrink faster than if you keep it close to 0%. So there's a big difference between using the lawnmower and then immediately topping off the tank vs. keeping the tank at 0% and only adding enough gas for one usage session just before you use it. It really doesn't matter if you use a full tank every week; if you keep it topped off at close to 100% during the 6 days it's not used and most of the hours on the 1 day it is used, that tank is going to shrink fast. What matters is the average level of gas in the tank over time because degradation (tank shrinkage in this example) happens continuously, and what you don't want to do is keep it close to 100% most of the time, even if you are using all of it every week.
 
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Previous poster in this thread said by his math the 18650s should have about 4% calendar aging after 7 years.

The calendrar aging is dependant on the. SOC and temperature.

Calendar aging is highest initially and reduce with the square root of time so for the first graph below (~about a year), that graph can be multiplied by
1.4 after two years
1.7 after three years
2 after four years
2.2 after five years
2.4 after six years
2.6 after seven years.

If the tesla cars show well below this value, it would be very interresting do perform a 100-0% drive and see how much energy actually can be drawn from the battery.
BMS-systems can not affect calendar aging so SOC x temp in the graph should be about right*

Down below two charts from Panasonic 18650 NCA that is either the same battery or very close to model S/X.


06EA1BF1-979D-4A18-A336-6A9F36E69DA2.jpeg



The chart below is the five first months, so basically the same as the chart above.
Comversion from 5 months to 10 (upper chart): value / square root (5/10)
Or more easy the value from below times 1.4.
54A0B298-DD6F-480F-B56C-0200ECD32818.jpeg


*) At least Model 3 and Y has a degradation threshold where the degradation does not show until the battery is below that threshold. This hide about 2% of the real degradation.
For S/X I dont have any knowledge of that.
 
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Dunno. I am naturally leary of attempting a 100 to 0 attempt. But going off of my trip meter from last charges and the kw usage I am somewhere between 74kw to 77kw of usable energy (guessing accessories are accounting for the discrepancies). My range during the summer is very solid as any trip beyond miles averages 250-260 watts/mi on highways so I am beating rated range.

The below are recent trips in cold weather (my commute to work). If you do the math it works out to about 74-76 kw of usable energy but I don't think the older trip meters include accessory usage.
 

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Dunno. I am naturally leary of attempting a 100 to 0 attempt. But going off of my trip meter from last charges and the kw usage I am somewhere between 74kw to 77kw of usable energy (guessing accessories are accounting for the discrepancies). My range during the summer is very solid as any trip beyond miles averages 250-260 watts/mi on highways so I am beating rated range.

The below are recent trips in cold weather (my commute to work). If you do the math it works out to about 74-76 kw of usable energy but I don't think the older trip meters include accessory usage.
kW is not a unit of energy, it is a unit of power.
 
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2020 MSLR here, 100kWh battery.
Does anyone know why the SOC percentage shown on the screen is different than the TesLAX and ScanMyTesla reading from the OBD? I notice about 2-3% difference at about 50-60% SOC.
How I found that? I am monitoring my degradation (Wh/m * miles left / SOC) and noticed that I get between 93% and 97%. Initially, I thought that it was because of different SOC (lower degradation at 90% SOC and higher degradation at 30% SOC) but then I thought that the screen value is most likely rounded. One percent SOC makes a difference in the formula I use, so decided to get a more accurate value from TesLAX and then noticed the difference. Does anyone know why is that?

On a separate topic. The car has 40k miles on it, 3/4 highway (65-75 mph). The average is 280 Wh/m which is way above the 250 Wh/m that would result in the EPA 405 miles range. Rarely used ski rack, so it is pretty much regular use. Anecdotally, on my trips I usually see around 270 Wh/m.
Has anyone seen such large discrepancy? That is 405 vs. 360 miles range, whole 10% difference!
 
Given the introduction of the "slider" I would like Tesla to give a number (percentage charge) that is optimal for the life of the pack. If you never (or almost never) need the full, or even standard charge range; what is the best level to charge to on a daily basis? Most driving days for me are less than 30 miles. What's my number? I'm certain it wouldn't totally end speculation. If Tesla engineers came up with a number for this scenario it would end any speculation for me.
We most often charge at 80% for daily use. Works well so far
 
2020 MSLR here, 100kWh battery.
Does anyone know why the SOC percentage shown on the screen is different than the TesLAX and ScanMyTesla reading from the OBD? I notice about 2-3% difference at about 50-60% SOC.
I’m not completely sure about S/X but model 3/Y use a 4.5% buffer below 0%.

At 100% displayed SOC the true SOC is 100%.
0% displayed SOC the true SOC is 4.5%.

The buffer is gradually hidden.
True SOC =
displayed SOC+(100-displayed SOC)x0.045

This means that the true SOC is about 2% (1.8 to 2.25%) higher than the displayed SOC at 50-60%.

The model 3 BMS (as seen by Scan My Tesla) report a lot of different SOC values. The on scren value is found but shown with one digit precision.
Of the pther values I think SOC minnis the ”true SOC” from the calculation above
How I found that? I am monitoring my degradation (Wh/m * miles left / SOC) and noticed that I get between 93% and 97%.

For the model 3, we do not see that big difference but as you divide by a rounded number the error increases with low SOC.
At 100% SOC there is no error in that calc but with a rounded number at 1% SOC the error can be as high as 50% of the calculated value.

At 30% SOC the error should be up to about 1.75%
 
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I read through the thread, but it is long so I may have missed it. If one wants to preserve battery life, I suppose it is fair to say that one should charge to as little capacity as you can but enough for what you need.

Does anyone have a good source for degradation as it relates to SOC, ie, 50% capacity no degradation; 75% capacity, 1%/yr of loss; 90% capacity, 2%/yr of loss, etc.

I suspect that most people don't keep their cars for much more than 5yrs, so it probably doesn't matter for the majority. However, if you are on this forum you probably like to know the data, just because.
 
I read through the thread, but it is long so I may have missed it. If one wants to preserve battery life, I suppose it is fair to say that one should charge to as little capacity as you can but enough for what you need.

Does anyone have a good source for degradation as it relates to SOC, ie, 50% capacity no degradation; 75% capacity, 1%/yr of loss; 90% capacity, 2%/yr of loss, etc.

I suspect that most people don't keep their cars for much more than 5yrs, so it probably doesn't matter for the majority. However, if you are on this forum you probably like to know the data, just because.

in europe people keep their car frequently >10 years and in eastern europe >15 to 20 years.
Less consumerism and americanism over there. I mean most people there dont buy new cars anyway.
there is a graph on teslafi but I only have 60k kms so its not that suggestive. maybe someone else can post it whos got higher milage.
 

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