Model S battery degradation data and/or model?

[ljwobker]

One of the folks over at the Nissan LEAF forums has built what appears to be a quite accurate spreadsheet that predicts the degradation of the LEAF battery over time, with a couple of key factors (miles, climate, etc) factored into the model. I have a LEAF myself and the model is accurate to within a couple of percent. WAs curious if anyone had run across similar data for the Model S. Before looking into this, I was under the impression that I knew a fair bit about how these batteries worked, but one thing that very much surprised me was how much calendar loss(*) there is on the LEAF battery, and was wondering if there was any similar info/data on the Model S.

Forum post link: http://www.mynissanleaf.com/viewtopic.php?f=6&t=14858
Spreadsheet itself link: https://docs.google.com/spreadsheet/ccc?key=0AqhUVOciAXVhdEFId2ppVEViZmd0ckJxME95N0U4SUE&usp=sharing


(*) calendar loss is the battery capacity loss from simply sitting there, independent of how much the battery is used/cycled. In the LEAF the initial year calendar loss is in the 10-12% range

 

[bint2k]

subscribed….. I'm sure data will be compiled soon enough

 

[djp]

Tom Saxton did a Roadster study for Plug In America, which found the degradation to be better than Tesla's original projections. Capacity loss is trending at 15% after 100,000 miles with no impact from climate.

http://www.pluginamerica.org/surveys/batteries/tesla-roadster/PIA-Roadster-Battery-Study.pdf

Tom is also collecting Model S data, I expect he'll publish a similar study once he has enough history for meaningful results.

 

[mitch672]

You can participate in the Model S survey, if you'd like:

Plug In America

 

[Zzzz...]

(*) calendar loss is the battery capacity loss from simply sitting there, independent of how much the battery is used/cycled.

Just to confirm, calendar loss is a known problem of li-ion. It is totally independent from use of battery cell. So loss is accumulated from the time battery was produced and have nothing to do with the use of the cell. The best practice to combat such capacity loss is to charge your cells to around 60% of SOC, and then store them in the fridge. Notice "fridge" not freezer. That helps a little bit. That is what I knew before I started to follow EV closely.

 

[TonyWilliams]

Tom Saxton did a Roadster study for Plug In America, which found the degradation to be better than Tesla's original projections. Capacity loss is trending at 15% after 100,000 miles with no impact from climate.

I drove 120 miles today from San Diego up north to Orange County, with about 15 miles range remaining.

That's 135 total miles / 3.7 miles per kWh is 36.49 kWh available.

36.49 / 41.8kWh when new is 87.28% capacity

19 months, 39,000 miles

 

[stopcrazypp]

I drove 120 miles today from San Diego up north to Orange County, with about 15 miles range remaining.

That's 135 total miles / 3.7 miles per kWh is 36.49 kWh available.

36.49 / 41.8kWh when new is 87.28% capacity

19 months, 39,000 miles

Where did you get the "3.7 miles per kWh"? That can throw your numbers way off. And is 41.8kWh the total usable, or is it the total capacity of the pack?

 

[shrink]

Where did you get the "3.7 miles per kWh"?

I'm guessing from the dash of the RAV 4 EV, which I think uses a 40 kWh Model S battery. miles/kWh is a common way of reporting efficiency and is used by the LEAF, RAV 4 EV, the BWM i3, Spark EV, etc.

I personally find miles/kWh much easier to conceptualize than Tesla's Wh/mile.

 

[David99]

I see a lot of interest and discussion about battery degradation and I understand it's a major issue car manufacturers have to tackle. It was a big factor when I researched what EV to buy. I've had terrible experience with lead-acid batteries in my first EV back in the early 90s.
One of the reasons I decided to get the Model S 85 was to eliminate the worry altogether. Both range anxiety and battery degradation. The 85 has so much range that even with significant battery degradation I'm still well within my driving needs. Even a 30% loss would still be OK for me. It would allow me to easily do my daily drive and get me from Supercharger to Supercharger without having to reduce speed.

I think this is where the key difference is between the Leaf (or any other current EV) and the Model S. In case of the Leaf, any loss of capacity is a serious concern as you often need all of it (especially with heater or AC going). Range is already limited, losing any is really bad. With the Model S the vast majority of people don't use the full range or even get close to it, thus it's less of a concern.

From what I gathered from different message boards the battery degradation on the Model S is very low. Mostly probably due to better cell chemistry, active cooling/heating and overall a lower stress on the battery.

Last but not least, by the time my battery has aged so much that it would be time to replace it, I'm pretty sure Tesla will have a better, more advanced and higher capacity pack available for the Model S which I would want anyways. The old cells get recycled and I'm happy getting a 100 kW pack (or whatever it will be).

So all in all, battery degradation is a non issue for me.

 

[jerry33]

I think this is where the key difference is between the Leaf (or any other current EV) and the Model S. In case of the Leaf, any loss of capacity is a serious concern as you often need all of it (especially with heater or AC going). Range is already limited, losing any is really bad. With the Model S the vast majority of people don't use the full range or even get close to it, thus it's less of a concern.

Yes, on my last trip there were headwinds so I lost range faster than usual. When I got down to 30 miles and the bar turned colour, I was thinking that if I had a Leaf or other EV, I'd be at half a charge, not at the point where the "you should start thinking about charging soon" warning appear.