Tesla Model S Battery Degradation Data

MAR 9 2015 BY MARK KANE 21

Tesla Shows Off The Model S Glider And 8,000 Odd Panasonic 18650 Cells That Power The Car Earlier This Year In Geneva

Tesla Shows Off The Model S Glider And 8,000 Odd Panasonic 18650 Cells That Power The Car Earlier This Year In Geneva

Batteries in general lose capacity over time and use, which for electric cars means lower range with every mile driven and every passing day.

How quick the capacity fade is remains mostly unknown as manufacturers typically provide only general information.

In the case of Tesla Model S, the warranty does not cover capacity fade.

Every car is used in different way, in different temperature ranges etc., so there is also no simple function that allows us to figure on what to expect in terms of capacity loss..

Over on the Steinbuch blog, we recently found links to reports based on data from Model S owners.

The first graph above (here is the interactive version) is described as follows:

“From the figure it is clear that the degradation slows down with more driven km. After say 80.000 km (50.000 miles), the overall range degradation is seen to be approximately 6%, with a rate of appr 1%/50.000 km (1%/30.000 miles) from that point onwards.

It’s hard to say how accurate these results are, but a loss of just several percent by 80,000 km (50,000 miles) should be considered as more than acceptable.

Especially positive would be that the pace of capacity fade seems to be stabilizing, but is it possible to extrapolate that you could drive 280,000 km (over 170,000 miles) and still be at some 90%?

We think that there are still too many factors and not enough data to say what to expect in the longer term.

Source: Steinbuch

Categories: Tesla

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21 Comments on "Tesla Model S Battery Degradation Data"

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The numbers actually don’t contain more details behind them.

o Number of superchargers used per 10,000 km.
o Number of range charges per 10,000

Stuff like that has impact on the battery degredation versus always normal-charging at home at 40A or some such rate. I read a battery research document that stated that the “rated range” for a range charge is when the batteries are charged above 4.2V to “full” capacity – can anyone confirm?

It would be interesting it a graph tracking LEAF battery degradation data was overlaid on the Tesla graph to compare the two batteries.

I think the reason why the Tesla batteries lose range a lot slower then the leaf batteries is they are under far less stress due to the Tesla’s huge range. When the leaf is used it’s batteries empty out a lot more and are charged a lot more the the Tesla.

Exactly, we’re trying to get down to cycle-life, and when you take a huge battery out for a 70 mile trip, you haven’t gotten near “1 cycle”. A Leaf, OTOH, has. A Volt only uses ~68% of its capacity, staying away from the full “cycle” that accrues toward killing it. Volt batteries are lasting. So, whether tons of range, or limited “depth of discharge”, you are going to get more miles from vehicles that feature one of these approaches.

Actually, the main reason the tesla’s battery degrades slower is that it can heat and cool its battery. The Leaf’s battery gets super hot when charging on a hotish day, while a tesla can regulate the temperature. Battery degradation is mainly caused by charging hot, not high current, which also means that superchargers have nearly no negative effects on a teslas battery capacity.

Care would need to be take so both LEAF and Model S samples had a similar distributions of vehicle age and vehicle milage (adjusted for cycle life based on capacity).

Note: the large an BEVs battery capacity, the lower the denigration expected miles accumulate. This is because battery life is based on charge cycle counts. (ie: larger capacity provides more miles per cycle … eg: how far will an EV travel on 1500 full charges?)

The other factor to managing denigration is battery shelf life. Cool well managed storage lower effects of secondary chemical reactions within battery cells.

PS: Notice little stated regarding charging current, speed, or SOC … these effect denigration much less the the first two factors.

I would appreciate that.
One thing to note is that the energy density of the Leaf battery is about half less than those of Tesla.
So there is less to loose with any percentage loss.

Mark nails the topic with …
“Batteries in general lose capacity over time and use”

Yes … two important, and independent factors:
1. Time (as in calendar shelf life), and
2. Use (miles, or accumulated charge cycles)

While the are a number of surveys tracking capacity vs. milage, few reports have tracked capacity over time. Both are important as each can effect the future value of an EV.

PS: if the raw data is available, it would be great to see a graph of Model S age vs. capacity (perhaps color-coded dots based on average annual milage) 😉

Visit the link. Merijn Coumans (the source of the data) posted some nice data regarding age, and he found no consistent difference in degradation per km for people with low km/yr (i.e. high time:use) and high km/yr (i.e. low time:use).

That’s a very good sign.

I noticed a Tesla with batt degradation sold very cheap on line. It had 90K miles and was a fully loaded P85 for 60K. Range had been reduced to 245.

I saw that one (sig red). 245 comports with 7.5%, after…..90,000….miles.

I suspect this is still a low sample rate of data, but I’m heartened to see more or less the same low percentage loss as in the last report I saw.

It looks very much as if having a big battery pack makes losing range happen much slower. So there is more than one reason PEV buyers are going to want a car with a higher range.

75000km and I have lost ~3km. Totally acceptable.

One thing to note here, it seems that the indicated range in the car is being used as a proxy for the battery capacity.

In reality, according to Tesla employees I’ve spoken to, the indicated range may show as being less than the actual achievable range because the charging pattern leads to inaccuracies building up in the car’s internal algorithm of battery capacity. As the charging pattern this is related to is also ironically the pattern that is best for the battery (using the battery between 40% and 80% SOC), it may well be that the lowest outliers in the graph above are actually the healthiest batteries in the fleet!

From what I’ve heard the only accurate way to gage a batteries capacity is to charge it up to the max and then discharge it until empty. However this is also the worst behaviour from a battery longevity point of view.

Well, if they are hiding the degradation then they are doing a good job of it 😉

What is the “typical” rate of current generation ICE engine performance HP and mpg degradation,assuming the factory-recommended service? I would think especially in the Prius crowd, there must be some published data.

The mileage on an ICE will typically get better over 50K moles becase all the part get worn in. The HP on a car that old will also near as much as new. Over 100K it is another story altogether.

That is assuming the owner properly broke in the engine, which is not always the case.

Some of the new ECUs also optimize the combustion over time, but I am not sure how much gain they can get out of that.

The big thing with the ICE crowd is the difficulty in measuring the degradation. How far can you get on a tank on the same tank of petrol after 100k miles? How much power do you have? You can also “tune” a ICE to increase power or mpg, I you can do that on a basic level by switching from eco to drive.

Conventional wisdom seems to be that a properly maintained gas guzzler will not experience significant loss of MPG for many years. Unfortunately, not all vehicles are well maintained. When I took an “Environmental Science” course in college (in the early ’80s), I learned that 10% of the vehicles on the road emit 90% of the pollution.

I see a claim at one website that “Vehicles that are 10 or even 15 years old will experience little decrease in fuel economy if properly maintained.” However, I’m rather skeptical that this represents reality. Worn rings, valves, and pistons cannot possibly maintain the engine’s original efficiency. Can even good maintenance prevent significant wear after 10+ years of normal use?

One factor I’ve noticed is that older vehicles tend to be driven less. Is that simply a reflection of the fact that vehicles which are driven more wear out faster, so are replaced sooner? Or is there actually a correlation between people who drive fewer miles per year keeping their cars longer?

For me, a new car creates excuses for driving, which wanes as the car ages.

I wonder if this has something to do with the steeper drop-off in the first 80,000 km … people be driving like crazy 😛