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Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health
- Thread starter KK_RedM3
- Start date
Candleflame
Active Member
the car hides the initial 24km of degradation. 463km is 11.4% degradation (1 - 463/523km).
navguy12
Active Member
Acknowledged.
When the car was new, my one “routine” twice a year long distance drive situation took two supercharger stops.
Yesterday that same drive took the same two supercharger stops.
So no change in the performance of that product in accomplishing its mission.
Two years since we purchased our M3LR, built June 2021 at Fremont.
Have been using AlanSubie4Life's est. of battery capacity since purchase.
(See sticky)
Calculating Your Battery's Estimated Capacity Using the Car's Energy Screen
Don't pay attention to range estimates much.
Typically calculate battery capacity after charging to 80-85% SOC at home.
Rarely/never? go over 85% capacity at home, rarely/never over 75% at superchargers.
When not being used the Tesla usually sits around 50% SOC.
In the last year, only 41% of charging has been at home (at <6kW) because of a couple of long trips.
Previous year would be much greater percentage at home.
So, I quesstimate about 4% degradation over 2 years?
(See graph)
Have been using AlanSubie4Life's est. of battery capacity since purchase.
(See sticky)
Calculating Your Battery's Estimated Capacity Using the Car's Energy Screen
Don't pay attention to range estimates much.
Typically calculate battery capacity after charging to 80-85% SOC at home.
Rarely/never? go over 85% capacity at home, rarely/never over 75% at superchargers.
When not being used the Tesla usually sits around 50% SOC.
In the last year, only 41% of charging has been at home (at <6kW) because of a couple of long trips.
Previous year would be much greater percentage at home.
So, I quesstimate about 4% degradation over 2 years?
(See graph)
I googled Ontario. Annual ambient temp 17C, so average battery temp smightly above that ( about 20C or a little higher).
If kept mostly at 50%, the degradation should be about:
2.5 x (square root (24/10)) = 3.87 ~ 4%.
So you’re spot on the plan
navguy12
Active Member
That is a good observation.
When I took delivery of my car, it was with the claimed range of 499 km and it showed 499 km as late as 2021:
As late as 2022, it was still showing 495 km at 100%:
AlanSubie4Life
Efficiency Obsessed Member
Not quite.
The original pack was 77.8kWh. This shows up even now on SMT reads of the RWD pack, AFAIK.
Degradation threshold with 325 rated miles (even on the RWD) was 76kWh for 2018/2019. This can be seen from the energy screen via the various methods described elsewhere. (Fundamentally, constant * “rated miles max” is degradation threshold)
What it was before the adjustment from 310 to 325 is not clear, but probably the degradation threshold was just 72.5kWh. (We’d need more early data before software change to say exactly.) I don’t know exactly, but have been told the rated-line position did not change, implying no change in constant.
It’s unlikely the pack was unlocked when increasing range from 310 to 325, because the EPA results didn’t change.
Still, can’t be 100% sure, but doesn’t really matter, since we know the state after the 310->325 change, which brought it in line with all the AWD vehicles (325 for RWD is the same as 310 on the AWD, neglecting degradation threshold effects).
The point here being that they could have just changed the degradation threshold, which would have the effect that the 310 rated miles before the adjustment would be really fat! I don’t know that any RWD owners saw loss of range before the adjustment (would have to review very old posts to see). This would be another way to rule out some possibilities.
69kWh (66kWh usable) vs. starting capacity of ~77.8kWh (74.3kWh usable).
67kWh (64kWh usable) vs. initial ~77.8kWh (74.3kWh usable).
77.8kWh FPWN for 2018/2019/2020 vehicles with LR pack.
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Perhaps a Loess smooth is preferable to the linear plot.
But it gives a simlar 95% C.I to the linear plot at the right edge:
~74-75.5 kWh at 2 years and 27.5K kms.
AlanSubie4Life
Efficiency Obsessed Member
Definitely a lot of jumpiness on the estimates. It tends to move in large steps. Reasons for unexpected (non-physical) increases seem to be randomness, weather (temperature presumably affecting the BMS estimates and their accuracy?), and software updates.
I googled Ontario. Annual ambient temp 17C, so average battery temp smightly above that ( about 20C or a little higher).
If kept mostly at 50%, the degradation should be about:
2.5 x (square root (24/10)) = 3.87 ~ 4%.
So you’re spot on the plan
View attachment 953429
Below is the square root formula applied:
Datapoint used, 50% SOC juuust below the 25C line, so 2.5% degradation during the first 10 months:
(Assumes the miles per month has ben about the same)
Drawn with my fingers on the mobile phone so not exact to the thousand of an inch.
It is probable that the real battery capacity did follow something like my drawn line.
Battery degradation is predictable and contrary to the BMS ups and downs, its a slope slowly reducing the sloping angle.
@brulaz; You probably will be at about 5.5% loss and 73.5 kWh after four years if you continue to use it in the same way.
We'll see! Will report back in a year or two with the latest data. Appreciate all the comments, people. Very informative forum.Below is the square root formula applied:
Datapoint used, 50% SOC juuust below the 25C line, so 2.5% degradation during the first 10 months:
(Assumes the miles per month has ben about the same)
View attachment 953652
Drawn with my fingers on the mobile phone so not exact to the thousand of an inch.
It is probable that the real battery capacity did follow something like my drawn line.
Battery degradation is predictable and contrary to the BMS ups and downs, its a slope slowly reducing the sloping angle.
@brulaz; You probably will be at about 5.5% loss and 73.5 kWh after four years if you continue to use it in the same way.
Candleflame
Active Member
Candleflame
Active Member
so data is in.
Battery is a 77.8kwh battery. 71kwh remaining (464km). 104 discharge cycles, 7369kwh discharge in total. so pack likely has 45-50000 kms on it.
Battery is a 77.8kwh battery. 71kwh remaining (464km). 104 discharge cycles, 7369kwh discharge in total. so pack likely has 45-50000 kms on it.
AlanSubie4Life
Efficiency Obsessed Member
Yep, as would be expected. Interesting how Tesla always has a pack available which is a good match.
Hopefully you’ll have better luck with this one.
Same here 57% on the MYLR dual motor (Australia May 2023 build) equates to about 300km estimated range. I drive daily and total about 300km/week and charge about 3x week to 57% - only because I don't need more and the estimated range is a nice round number and easy to see if it changes over time. I could charge to 40% and still be comfortable with available range
I am interested in your views about Jeff Dahn's recommendations a few years ago to charge to 70% SOC
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Is it possible that they are somehow software nerfed to behave like a "used" pack?
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