Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

[DrChaos]

First of all:
Your battery will be fine without any special handling from your side. Thats the way Tesla have managed it. No need to be a battery engineer.
Teslas advice in short: Always connect the charging when possible. Only charge above 90% for longer trips. Thats it.

But this will not be the same thing as minimizing the degradation to a minimum. Teslas advice is aiming to make the EV owning easy.

I have written a lot of posts about this. If you would like to keep the degradation to a minimum, you can do that. No need to, but if you for any reason would like to, its possible.

Lithium ion batteries degrade from calendar aging and cyclic aging. For most, the calendar aging is the dominating degradation early in the cars life. Cyclic aging comes from the cycles.

Low SOC wears less on the battery. Calendar aging is least at low SOC and highest at high SOC.
Cycles wear less at low SOC. Also, smaller cycles wear less than larger cycles.

- Charge often. This will keep your cycles small.
- Dont charge to a higher SOC than you need. If you really need 90% each day, use 90%, or charge one extra time each day and use lower SOC. If you only need 50%, charge to 50%.
- If possible, charge close in time before using the car. This reduce the time the car stands with high SOC.

I have written a lot of posts with detailed description of the fundamentals behind the advice above, taken from a lot of research about lithium ion batteries. Do a search on my posts if you need more info.



100% on the screen is 100% real SOC. The bransch standard for this type of lithium ion batteries is 4.20V/ cell = 100% and thats what Tesla also use. When you read 100% the cells will have 4.20V/cell. If you try to measure it, or as most people use Scan My Tesla, you will se 4.19x or something, but this is because the car always is on, using a little power when yo can check the voltage.
The charging stops at 4.20V/cell. I have a lot of ”evidence” for this, but at this point I think we can skip this part. Just trust me and the other ones that say so.
0% on the screen is 4.5% ”true SOC” of the capacity that Tesla calculates, those 4.5% is the buffer below 0% on the screen.

This is a map of my degradation so far, 14 months and close to 35.000km. I follow my advice above, charge to 55% daily and my charge setting charges just in time so most nights my car sit at 20-35%SOC. I havent really lost any range but the other cars of the same type (model 3 performance 2021) have lost 5% in average. My car has lost least of all.
View attachment 777212

Amazing! Thanks so much. Could this be made a permanent 'sticky' post? Would help so many. I have a smallish commute so I will charge only up to 50-60% per day. I have L2 at home (coming from a BMW i3) so I'm used to daily charging, and because SDGE has such extortionate rates, charging only on super-off peak at night.

I knew about calendar aging & cyclic aging, but I had assumed that in typical cars, cyclic aging was the dominating effect. It sounds as though it is not so! A surprise to me. Everything I read about batteries concerned how to "get more cycles", so I assumed that was the primary engineering figure of merit and calendar aging wasn't a practical problem. Your post is enlightening---I've downloaded and read academic battery papers for years ("for fun") but never got to any consistent practical recommendations other than "don't be really cold or hot". The fact that not all cycles are equivalent in terms of aging, even given total energy being equal (i.e. same overall energy use but in different cyclic patterns and SOC), is also an unobvious result.

The BMW i3 manual recommended charging up to 100% (though its 100% is not true 100%) every day. There is no charge limit that can be set anyway. Batteries are Samsung NMC.

 

[frodebh]

As been pointed out elsewhere you have seen the 580 km figure in Teslas European marketing materials, they can market according to the less demanding standard WLTP here. But when you get in the car you will see the lower EPA-based range estimate, which can be a disappointing surprise until you get information on why this is.

However, I guess if the stars align perfectly, there are no black cats around and all the conditions are on your side you should be able actually reach WLTP range with perfect driving? Or is the WLTP just too artificial?

Took delivery of my M3LR on September 30. last year, so I am also a happy and proud member of the E5CD with a rebate club! Because of Covid and chip shortages I didn't get my home charger installed until last week so I haven't actually tested charging to 100% yet, but with my basic calculations having driven close to 9000 km, range is looking very good. Looking forward to test full charge range next weekend!

At around five months and 9100km exactly, the car showed 546km range after being charged to 100% plus an hour. A decent number.
This car has been charged at supercharges mostly and exclusively for the first month I had it.

Curiously, the range estimate jumped to 549km when I put the car in drive and then came back down to 546km after a couple of hundred meters.

 

[conv90]

I think the energy meter in the car should be good enough also. Charge full and drive until the car almost stops and read the consumption details. The SMT cell voltages would help to extrapolate the last few drops of energy.

Charging and reading the consumption outside the car(or even inside) will not show the capacity of the battery. There are losses that will be included in the total.

Well, good thinking Dave! This is anyway one of the first things to consider to make sure that the BMS is right, or to learn its not.
I have a plan to do this with my car to see what the real capacity is. I have 80.5kWh NFP according to my BMS, and did charge full a few days back and did get 80.6 kWh remaining. I had a NFP of 80.6kWh when I first connected the SMT, after one day since I got the car.
I plan to do it to check my batt’s real capacity but it probalby will be a good reference to other doing the same thing.

I want to do it a day... the only concern is to do the 100% to 0% (or even to -4,5%) in a single trip. Stops will screws the results.
Today I discharged the car to 0.
What I obseved is that cell imbalance were near 40 to 50 mV when at 5 or 6 or 7%, so I decided to go near zero to monitor imbalance.
Usually I have at half battery at 4 to 6 mV, then it increase a bit when the soc is under 20%.
I was afraid because 50mV imbalance can let you down even if you have a good amount of mV on average in the cells. what is important related to shout down is the lowest cell, not what SMT says on SOC or Buffer.
But, starting at 4 or 5% and down to 2 and 1 and 0% the imbalance went down progressively to a better value (18 mV) .
Looking at 18 mV like a safer imbalance compared to 50 mV, I said to myself to go some into the buffer, because 18mV is a good low value consiedered the bottom of the battery capacity.
I used up to 1,2kWh of buffer and about -1,60% SOC expected and same -1,60 kWh SOC. Ideal remaining and Exp Remaining were 2,20 kWh (from 3,40 buffer)
What I never understand are the values of SOC UI at +3,80%, SOc MIN +3,00% and SOC MAX still at +5,00% and SOC Avg at 4,60%

 

[AAKEE]

@DrChaos This is the basics about calendar aging:

Calendar aging ”eat” about 5% the first year for most people. It is quite temperature dependant but most people either can affect the ambient temperature or know about this part so to be tactical with the SOc is the only remaining option.

Calendar aging is worst in the begining but lessens with (about) the square root of time. If first year causes 5% you will not reach 10% until four years( square root of four = 2 —> doubled the first years aging after four years).

Worst case scenario for cyclic aging is that the battery holds upp for about 500-1000 cycles before the degradstion reaches 20%( thats the industry standard, so research tests use 20% degradation) if its used 100 to 0% each time.
Lets call that 750 cycles @ 350km =262.500 km, for a cyclic loss of 20%.
Most people do not use those full cycles so the battery wear is much less / cycle pr km driven.
The average car in sweden is driven about 12000km a year, so we are looking at about 1% (or much less) each year for a average driven car.

In average we probably have some 5% calendar aging the first year but less than 1% cyclic aging.

 

[Dcam]

you say: "
Do we
Know anyone that use low SOC and have lost a lot?"
Me . and you know that I cosider you a guru.
probably not "a lot".... but 73,8 kWh from theretical 82,1 it's a lot expecially if in 11 months and 22k km.
I asked to Tesla (a guy I Know).
He said I have a AVERAGE SOC of 39% . He said : " a very low average compared to the average user : 73%"
He have NOT said "too low average soc, so you have more average degradation". He simply said my car sat very low on SOC.
I'm conviced that my battery is a bad battery (under average).
This change my way to use it ? no. I have problem with range? no.
I'm happy of my car? YES.
I'm a bit disappionted (expecially if compared to other cars of my friends that don't take care of the battery like me and always charges to 80 or 90 or 100 night and day and let the car sleep at 90% and haves LESS degradation) ? YES.

If you gain weight or store stuff in the trunks the range changes.

 

[AAKEE]

I want to do it a day... the only concern is to do the 100% to 0% (or even to -4,5%) in a single trip. Stops will screws the results.
Today I discharged the car to 0.
What I obseved is that cell imbalance were near 40 to 50 mV when at 5 or 6 or 7%, so I decided to go near zero to monitor imbalance.
Usually I have at half battery at 4 to 6 mV, then it increase a bit when the soc is under 20%.
I was afraid because 50mV imbalance can let you down even if you have a good amount of mV on average in the cells. what is important related to shout down is the lowest cell, not what SMT says on SOC or Buffer.
But, starting at 4 or 5% and down to 2 and 1 and 0% the imbalance went down progressively to a better value (18 mV) .
Looking at 18 mV like a safer imbalance compared to 50 mV, I said to myself to go some into the buffer, because 18mV is a good low value consiedered the bottom of the battery capacity.
I used up to 1,2kWh of buffer and about -1,60% SOC expected and same -1,60 kWh SOC. Ideal remaining and Exp Remaining were 2,20 kWh (from 3,40 buffer)
What I never understand are the values of SOC UI at +3,80%, SOc MIN +3,00% and SOC MAX still at +5,00% and SOC Avg at 4,60%

Did you allow the car to sleep with that low
SOC? A Open Circuit reading will tell the BMS the real SOC (as the true SOC is read as a voltage and the battery need to be without any kiad to show the real resting voltage.) Did you see any cell voltage at around 0% SOC?
I have not digged to the different SOC values so for now I pass that part. UI should be User Interface, what we see on the screen?

We actually do not need to drive the car down until it stops if the goal only is to find the capacity, if we think the BMS isnt very off. We can drive until 0.0% and calculate the 4.5% buffer.
A voltage reading taken at 0.0% will tell us
about differences Between the BMS percieved SOC vs the real SOC.

If we think the BMS is off, and other actions didnt help, driving the car as low as we dare and also letting is sleep for at least a while at very low SOC will help the BMS to find the lower end of the battery capacity.

 

[DeltaOne]

Calendar aging ”eat” about 5% the first year for most people.

In average we probably have some 5% calendar aging the first year but less than 1% cyclic aging.

My Model 3 is just a few weeks shy of a year old. Delivery March 27, 2021. First check up on the battery was May 25th. I also checked it yesterday.

If I'm doing the math right I've lost approximately 5%. Does my math look right?

 

[conv90]

Did you allow the car to sleep with that low
SOC? A Open Circuit reading will tell the BMS the real SOC (as the true SOC is read as a voltage and the battery need to be without any kiad to show the real resting voltage.)
No, I have not allowed to sleep with sub 0%. I only tried to go under 0% being near to a AC public charger.

Did you see any cell voltage at around 0% SOC?
YES, 3,052 (min) to 3,070 (max), 18 imbalance when car was stopped and me out of car with the car consuming 0,32 kW , so not sleeping.
I really don't know the max allowed lower limit of cells before shout down.
I have not digged to the different SOC values so for now I pass that part. UI should be User Interface, what we see on the screen?
Yes the UI seems to suggest User Interface but it's NOT. screen was displaying 0% even when SOC expected -1,6%, SOC UI is +3,8%

We actually do not need to drive the car down until it stops if the goal only is to find the capacity, if we think the BMS isnt very off. We can drive until 0.0% and calculate the 4.5% buffer.
A voltage reading taken at 0.0% will tell us
about differences Between the BMS percieved SOC vs the real SOC.

If we think the BMS is off, and other actions didnt help, driving the car as low as we dare and also letting is sleep for at least a while at very low SOC will help the BMS to find the lower end of the battery capacity.
I'll try, now that I'm confident that the car can really do additional kilometers uder 0%... even if I don't think the BMS is OFF or bad calibrated. Unfortunately i Think that 73,9 / 74,0 kWh is correct.

 

[AlanSubie4Life]

My Model 3 is just a few weeks shy of a year old. Delivery March 27, 2021. First check up on the battery was May 25th. I also checked it yesterday.

If I'm doing the math right I've lost approximately 5%. Does my math look right?


View attachment 777754

I think so. Your rated range at 100% should be down by about 5% from new too (I can't recall off the top of my head what this particular model had when new...my memory is failing me since there were so many variants of the SR+ when it got near end of life). Yours was not an LFP, AFAIK.

 

[Jejunjm]

had to look up chandler. What is this hell on earth and how do you have hell only a few 100 kms away from i.e. san diego where its... nice

However, it is a dry heat. It's more like 4.3 million people in the Phoenix metro area. They must be on to something. Maybe they like scorpions

I live in Arizona (for the past 14 months) It's actually great. I'd much rather live in San Diego or Hawaii but cost of living...

Monsoon season is .... Interesting

 

[AAKEE]

YES, 3,052 (min) to 3,070 (max), 18 imbalance when car was stopped and me out of car with the car consuming 0,32 kW , so not sleeping.

I was down to 0.39% SOC just to test last summer.
3.090V/cell (3.082-3.098) with 16mV imbalance (consumption load of 0.39kW).

It sure do not look like your BMS is very much of track. So we probably will not find a bunch of kWh there :-(

 

[Candleflame]

I was down to 0.39% SOC just to test last summer.
3.090V/cell (3.082-3.098) with 16mV imbalance (consumption load of 0.39kW).

It sure do not look like your BMS is very much of track. So we probably will not find a bunch of kWh there :-(

you mean true SOC or displayed SOC?

I took a reading few months ago at 0.46% SOC (true SOC 5 to 7.1%) and I had imbalance 16mv and cell voltage was around 3.060V
so sounds like you have perhaps a bit more juice than what the car suggests.

 

[AAKEE]

you mean true SOC or displayed SOC?

I took a reading few months ago at 0.46% SOC (true SOC 5 to 7.1%) and I had imbalance 16mv and cell voltage was around 3.060V
so sounds like you have perhaps a bit more juice than what the car suggests.

At SMT ”just” SOC and from memory the scren showed 0%.

My guess is that my BMS overestimate the capacity slightly from often staying low in SOC. On the other hand I always get a little more stuffed in than the NFP when charging full.
One week ago I did a full charge, leaving for my new job, 240km drive and no SuC in that place. 507km on the screen and Nomimal remaining was 80.6, NFP still at 80.5kWh.

By the basic principle of calendar aging, I should have lost some 2% or so and perhaps 0.5-1% for the cyclic part.
Should be around 79-79.5kWh according to my calcs (which is not 100% exact, but I probably is not very far from my calculations. This os the reason for me to have planned a 100-0% drive to get a ”real” check of the capacity.

[Edit]By memory my SMT Soc and screen values follows close, it switches over very close to the half percent rounding.

 

[Undecided_2]

I’m a total newbie and I’m picking up my Y tomorrow. I originally was going to treat the car the same as my laptop. I don’t leave it on charge all the time and let it run down a little before topping up. Based on what I’ve read here It would be okay to keep the car charged to around ~50% daily as that will cover our needs for most of the month and occasionally take it to 100% once or twice a month?

 

[AAKEE]

I’m a total newbie and I’m picking up my Y tomorrow. I originally was going to treat the car the same as my laptop. I don’t leave it on charge all the time and let it run down a little before topping up. Based on what I’ve read here It would be okay to keep the car charged to around ~50% daily as that will cover our needs for most of the month and occasionally take it to 100% once or twice a month?

First of all, the very simple advices Tesla gives is fine. It might cause a little bit more degradation than the lowest possible but it will be easy/causal to own a Tesla.

Yes, 50% is good.

You could keep it connected and charge daily to 50%.
There is no need to let the car drain to lower SOC. Lower SOC cause lower calendar aging, but introduce larger cycling.
Per definition cycles wear less than time but the 50% will cause small degradation anyhow.
If not connected daily you might end up with too little SOC for a planned drive?
There is really no negative part for the battery if you charge to 50% and let it drain until low SOC, so you for sure can do that.

I seem to do about one full charge each month or so, charge to 55% daily ( I charge just before the drive so my battery average SOC stays low, most nights 20-30%).
I have had very little degradation so far.

 

[Undecided_2]

I’ll leave it connected and set it to 50%. It’s all stuff that I’ll learn and ultimately it’s not a hassle to set it to 100% charge as it be ready in the morning. The bulk of the cars charging will be at home anyway and based on what I’ve learned here is probably better for the battery long term.

 

[Apprunner]

I’m a total newbie and I’m picking up my Y tomorrow. I originally was going to treat the car the same as my laptop. I don’t leave it on charge all the time and let it run down a little before topping up. Based on what I’ve read here It would be okay to keep the car charged to around ~50% daily as that will cover our needs for most of the month and occasionally take it to 100% once or twice a month?

Why do you take it to 100% once or twice a month? Really no need for that at all. BMS calibration is highly overrated and really doesn't need to be done much at all. Only take it to 100% if you absolutely need the range that day but no need to arbitrarily take it to the max charge as its actually not great to do that to the battery.

 

[kavyboy]

I’m a total newbie and I’m picking up my Y tomorrow. I originally was going to treat the car the same as my laptop. I don’t leave it on charge all the time and let it run down a little before topping up. Based on what I’ve read here It would be okay to keep the car charged to around ~50% daily as that will cover our needs for most of the month and occasionally take it to 100% once or twice a month?

The only issue with that is if you have an unexpected trip that requires more than 50% and don't have time to charge before leaving. I've had that happen a couple of times. Now I just charge to 90%. I bought the car to drive it, not babysit the battery.

 

[Undecided_2]

The only issue with that is if you have an unexpected trip that requires more than 50% and don't have time to charge before leaving. I've had that happen a couple of times. Now I just charge to 90%. I bought the car to drive it, not babysit the battery.

That’s a fair point! Tesla do say to just keep it charging and to charge it fully before a big trip.

 

[Apprunner]

That’s a fair point! Tesla do say to just keep it charging and to charge it fully before a big trip.

Do whats right for you but a counterpoint is that the one time I need it for a long drive and my battery is at 55%, i can top off at a Supercharger for 10 min and not worry about it. Supercharging when needed doesn't harm the battery and seems silly to have unnecessary degradation related to the off-chance that I "may" encounter a need for a long distance trip once every blue moon. Its kinda like the same argument that ICE owners have about EVs where the EV doesn't meet their one a year roadtrip requirement so they refuse to look at EV ownership.