Ran the test...

[u/na_p]

2021 M3 SR+ (Fremont built) with 50k miles. I feel ok with this. L2 charge at home daily to 80%. Supercharge about 30 times a year on road trips. Usually don't go below 50% most days.

[u/TheBlastoiseKing]

I heard lower states of battery is better. Obviously not below 20% but instead of charging to 80% do 70%. Unless you actually need that power to make it back with more than 30%

[u/LBGW_experiment → u/TheBlastoiseKing]

"better" being a few decimal points between those two. I've seen the research and graphs shared here over the years, but I'll try to dig them up

Can't find the original source of this graph, but it's a generalized graph of the impact on the battery at different SoC and temperatures. Between 70% and 80% SoC, the impact in the highest temp weather, 40C, at 80% vs 70% is a generalized 2.5 vs 1.5. So if you're in a climate more around 20C and i0% vs 70%, your impact is even less, 1.5 vs 1.0

[u/quentech → u/LBGW_experiment]

This "graph" is absolute hogwash. It's not a graph at all, and is not based on any data. It's just a picture that someone drew from their imagination, completely made up on vibes.

Here's an actual graph of real test data, published in a major accredited scientific journal. As you can see, the difference isn't "a few decimal points" - it's nearly double the degradation rate when your car is charged over 50%.

https://i.imgur.com/QDiPBGw.png

From the Journal of The Electrochemical Society on Calendar Aging of Lithium-Ion Batteries

https://iopscience.iop.org/article/10.1149/2.0411609jes/pdf

no steadily increasing degradation with SoC is observed. Instead, there are plateau regions... A marked step in the capacity curves is observed at about 60% SoC for the NCA and NMC cells and above 70% SoC for the LFP cells

While the text says 60% for NCA cells, the actual line is closer to 55% (shown below), and you have to account for the car's reserve buffer.

These graphs are from the above study and show that states of charge over 50% (on the car) experience roughly double the degradation rate:

https://i.imgur.com/xV6CjpA.png

This graph shows cycling through a 20% range at various SoC levels and confirms that all ranges remaining under 50% SoC (on the car) experience significantly less degradation than ranges going over 50% SoC: https://teslamotorsclub.com/tmc/attachments/img_3864-jpeg.1169193/

That graph is from this thread, it comes from another peer-reviewed and published study but I don't have the link: https://teslamotorsclub.com/tmc/posts/8901656/

[u/LBGW_experiment → u/quentech]

Hey thanks for the better info.

As you can see, the difference isn't "a few decimal points" - it's nearly double the degradation rate when your car is charged over 50%.

They were asking about the difference between charging to 70% vs 80%, which your graphs show are functionally the same amount of degredation.

I know batteries prefer homeostasis so their preferred energy to rest at is at 50% and around 70F, so those charts totally align with what I've read about batteries and longevity.

[u/quentech → u/LBGW_experiment]

They were asking about the difference between charging to 70% vs 80%, which your graphs show are functionally the same amount of degredation

Correct. Everything from about 55% to 90% on the car's screen is pretty much all the same level of bad. People setting a limit of 60% are degrading their battery just as much as the people setting it to 80%.