Oh, no!
80% is most probably the worst SOC to use. In some cases worse than 100%.
The baby-by-80% is a myth
This chart shows actual Tesla Model S cells taken out of a 6 months old model S.
In this case, 80% was worse than 100%.
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This is Panasonic 18650 NCA cells, as close as you get without doing like above:
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We can see that 80% is worse than 100%, this time also.
This is 2170 NCA cells of a non disclosed brand:
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As there are not very many 2170 brands with NCA chemistry, it is a good chance the actually used panasonic 2170.
I bought 35 pieces of Panasonic 2170 and from my tests, I did get redults very similar to the second from above research graph.
There are a lot more research reports testing Panasonic NCA cells, closely related to the cells Tesla use.
This one do not show that 80% worse than 100%. On the other hand, 80% and 100% is more or less as bad (or good if you like).
We can see that staying at 55% or lower is reducing the calendar aging by half.
Shortening the time above 55% to a minimum, or avoiding completely will reduce the degradation rate to half.
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First of all, if you follow the Tesla advice to charge below 90% (thats 50-89%) for daily driving the battery will be fine.
But it will not have the lowest degradation.
I suggest you follow this advice if you like to reduce the degradation:
-Charge often
-Do not charge more than needed until next charge (which is soon as per the above statement).
-Charge late. Calendar aging is the dominant degradation factor and shortening the time at high SOC will reduce degradation.
The lower the SOC, down to 0% SOC, the less degradation. The largest single win is by having the battery on the lower side of 55%. (This statement means - low SOC is really good - 80% is not really good)
Low SOC, below 20% or below 10%, is good. It is
not bad for the battery at all - that’s a myth.
100% SOC is not as bad for the battery as the forum myth says. You do
not need to drive asap as the degradation is about the same as at 80%. But as there is no reason to have the car parked long time at 100%, you should not leave it like that. You should not leave it at 80% either as it is about as ”bad” as 100%.
This is my M3P after 2 1/2 years, 64.000 km (like 40K mi). The blue line = my car
Green= the average other M3P that use teslafi.
I use 55% as the daily charging level.
I charge every day.
I charge late, somthe charge is finished shortly before the drive.
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My car has used really low SOC a lot.
Usually parked at work for one week at the time with about 7-20%.