Not quite another degradation question

[KenBlub]

I bought a 2023 Model 3 RWD in mid May 2023. It had 15 miles on it. Per the VIN it was made in California in January 2023. Almost have 4000 miles on it. Tessie says I have .9% degradation. I assume it's calendar degradation but is it 6 months or 2 months. I'm trying to create a graph of battery capacity

FWIW Tessie says 59.7kw capacity so I figured my earliest capacity was 60.3. Sound about right?

How accurate is multiplying wh/mi x range ÷ SOC. The average of my 5,15,30 results in 59.93. Is one of the 3 (5-15-30) more accurate or is an average of the 3 best.

Props to this forum. Charge my LFP to 55 every day and 100 every 2 weeks always setting a departure time. I want this to be the last car I ever own

 

[AAKEE]

I bought a 2023 Model 3 RWD in mid May 2023. It had 15 miles on it. Per the VIN it was made in California in January 2023. Almost have 4000 miles on it. Tessie says I have .9% degradation. I assume it's calendar degradation but is it 6 months or 2 months. I'm trying to create a graph of battery capacity

FWIW Tessie says 59.7kw capacity so I figured my earliest capacity was 60.3. Sound about right?

Full pack when new is 60.5 kWh on the later LFP’s.

How accurate is multiplying wh/mi x range ÷ SOC. The average of my 5,15,30 results in 59.93. Is one of the 3 (5-15-30) more accurate or is an average of the 3 best.

The precision of the calculation is down to the rounding of the SOC %.
The higher the SOC, the lower the margin of error.
At 100%, if the charging just stopped it should be spot on.

At 80% the rounding is causing a margin of error of 0.5/80 = 0.6%.
At 10% SOC the margin of error is 05/10= 5% (This is for the SOC part, there is a similar error for the average consumtion and range but they both are mistly numbers above 100, giving very small ertor margin. Higer SOC, higher range —> better resolution)

Use high SOC for this and you’ll be fine.

As 5-15-30mi, do not really matter. Use all three and make the average calc if you like a better precision.

Props to this forum. Charge my LFP to 55 every day and 100 every 2 weeks always setting a departure time. I want this to be the last car I ever own

The battery probably will hold up anyway for 10 years or more but if you like to reduce the degradation:

LFP’s has 70% as the highest SOC number with low calendar aging, so ypu can do 70% without a problem.
Look at the LFP chart.
(All three for reference, 55% is NCA)
55% is as good as 70% for LFP, not worse but so you know you can use 70% and still have low degradation.
To be exact its about 72% true SOC but due to buffer offsetting the dispkayed SOC 70% is the number to use.

Charge late and use 100% often enough to help the BMS keep the track is good.

 

[KenBlub]

Thanks for the great info. I tested at 40% SOC so I’ll redo the calculations

Made in January and purchased in May. For my degradation chart, is the battery 6 months old or 2 months?

 

[RayK]

I'm sure you'll get a good opinion from @AAKEE but were it me, I'd half the difference and call it a 4 month old battery. Two months difference in the calculations should be that much of a change.

I would think that the most important information is not available to you. Namely, the state-of-charge and/or the charging that was (or wasn't) done on the battery while it was sitting those four months.

 

[AAKEE]

Thanks for the great info. I tested at 40% SOC so I’ll redo the calculations

Made in January and purchased in May. For my degradation chart, is the battery 6 months old or 2 months?

As you do not know what SOC it had for the time before you bought it I guess you can not use the calculation anyway.

Per definition I would call it 6 months, and count from the Full Pack when new initial value. I would guess Tesla do not store the cars at higher SOC than 50%, but I do not know.

For overseas transport they have started to use low SOC due to new off shore regulations (they offer a 150km free supercharging session as a compensation.
I did get my model S recently with 40% SOC.

As RayK sas, it do not make a noticebla difference in the long run if you use 2 or 6 months today.

I think using 6 months, SOC = 50% and a reasonable tempersture and you have a good expected starting point.

50%, 25C and 6 months would put you at somwhere between 2 and 2.5% I guess:
Lets say 2.25% loss

That would put you at about 59.1kWh.
This is not a exact value, as we have guessed both average SOC and temp.
(Also I took the 2.25% by eye measurement)

 

[KenBlub]

Thanks. I feel good. Tessie says I’m at 59.7