With another couple of "high profile" threads highlighting the issues with battery degradation, as well as the advances in battery chemistry between the Roadster and the Model S, I got to thinking about expected battery life for my circumstances.
It's been suggested (bothe here, and in various whitepapers and articles by Tesla and others), that the Roadster used earlier Li-ion technology (Li-Ni?) that would be good for ~500 full discharge cycles before having degraded to a specific point (70%).
The Model S has a newer chemistry (NCA?) that has rumored to be good for 2,000+ cycles to get to the same point.
As the rating is based on full discharge cycles, it's understood that two 50% discharge cycles is equivalent to a full cycle (more or less)... and is the same for four 25% cycles, etc... It's also understood that those shallower cycles in the "middle" of the charge range is better than extremes at the top or bottom of the range.
So, I'm almost exactly at 2,000 miles a month on my S85. That averages to 67 miles a day over 30 days. It just so happens my weekday commute is about 66 miles. Apparently my weekend driving keeps up this average pretty closely.
That's also just almost exactly 1/4 the range of a full charge. Which matches my typical charge at night I charge to 60% and typically plug in around 35% at night... or about 25% of charge I add nightly on average.
So... if the expected pack life is 2,000 full cycles, I could be looking at 8,000 of my average nightly charge to reach the same point. That's 22 years.
Now, I don't expect I wont see degradation before then... as there are ather factors such as just calendar age, etc... but as long as the thermal management of the car is doing what it should it will be interesting to see how well our packs retain capacity over time...
It's been suggested (bothe here, and in various whitepapers and articles by Tesla and others), that the Roadster used earlier Li-ion technology (Li-Ni?) that would be good for ~500 full discharge cycles before having degraded to a specific point (70%).
The Model S has a newer chemistry (NCA?) that has rumored to be good for 2,000+ cycles to get to the same point.
As the rating is based on full discharge cycles, it's understood that two 50% discharge cycles is equivalent to a full cycle (more or less)... and is the same for four 25% cycles, etc... It's also understood that those shallower cycles in the "middle" of the charge range is better than extremes at the top or bottom of the range.
So, I'm almost exactly at 2,000 miles a month on my S85. That averages to 67 miles a day over 30 days. It just so happens my weekday commute is about 66 miles. Apparently my weekend driving keeps up this average pretty closely.
That's also just almost exactly 1/4 the range of a full charge. Which matches my typical charge at night I charge to 60% and typically plug in around 35% at night... or about 25% of charge I add nightly on average.
So... if the expected pack life is 2,000 full cycles, I could be looking at 8,000 of my average nightly charge to reach the same point. That's 22 years.
Now, I don't expect I wont see degradation before then... as there are ather factors such as just calendar age, etc... but as long as the thermal management of the car is doing what it should it will be interesting to see how well our packs retain capacity over time...
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