Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Tesla Model S battery degradation data

steinbuch.wordpress.com

Post reply on HN
Print view View original

31–40 of 257 posts

Re: Tesla Model S battery degradation data

#31

Post by rcthompson »

RachelF wrote: post #11
mschuster91 wrote: post #2

What could explain the graphs and cycle stability is that Tesla does not deplete the battery pack below a certain percentage of the real battery capacity or over a threshold... basically they keep the battery pack well beyond the critical ranges where batteries degrade from simply idling, and they "undersell" the pack capacity.

I've always wondered how they do it. They use the same 18650 cells that power laptops, yet laptop batteries degrade badly over time. My 1 year old XPS13 reports a battery "wear level" of 29%. I wonder if Tesla's battery technology could be used in laptops and phones?

I think the idea is if you programmed your laptop to never charge the battery past 80% or discharge it past 20%, it would degrade much more slowly, but you would also get about 40% less battery life out of a single "full" charge. Or you would need to increase the battery mass by 66% to get the same battery life. Laptops need to be light enough for a human to carry, while cars don't, and cars are generally expected to last longer than laptops, so the second solution is probably more viable for cars.

Re: Tesla Model S battery degradation data

#32

Post by leggomylibro »

RachelF wrote: post #11
mschuster91 wrote: post #2

What could explain the graphs and cycle stability is that Tesla does not deplete the battery pack below a certain percentage of the real battery capacity or over a threshold... basically they keep the battery pack well beyond the critical ranges where batteries degrade from simply idling, and they "undersell" the pack capacity.

I've always wondered how they do it. They use the same 18650 cells that power laptops, yet laptop batteries degrade badly over time. My 1 year old XPS13 reports a battery "wear level" of 29%. I wonder if Tesla's battery technology could be used in laptops and phones?

I wonder if they're particularly good at balancing the cells. When people recycle 18650s from laptops, I think it's often because one or two cells went bad while the rest remain fairly healthy.

Similarly, if you put things like batteries or capacitors in series, you typically want circuitry to balance their voltages, because a pair of 2.7V elements charged to 5.3V could really be at say, 2.75V and 2.55V, which would be unhealthy for the former cell. I think those imbalances are also caused by small differences in the individual elements' properties (capacitors are typically less precisely-tuned than resistors) which will drift further over time with wear and temperature changes and overvoltage conditions and whatnot. So that 2.75V cell would degrade very rapidly compared to the 2.55V one, probably causing even larger imbalances until it eventually fails.

Most lithium cells have basic protection circuits built-in against over/under voltage and overcurrent (e.g. shorts,) because they tend to explode if you leave those things out, but they definitely last longer if you pay attention to them as individual cells rather than a system.

Re: Tesla Model S battery degradation data

#33

Post by sorenjan »

TomMarius wrote: post #7

Average life of ICE vehicles can't be 266kkm, that's absurdly low. Most of people I know have bought vehicles with that mileage and used it for another 100kkm after that at some point in their life (think first/second car, second family car, etc.). It's important to know that especially in Central/Eastern Europe, you can never trust the car's odometer - even the cars I'm talking about had probably more than 350kkm wh…

I've never seen anyone put more than one kilo before the unit before.

Re: Tesla Model S battery degradation data

#35

Post by sqeaky »

dmitrygr wrote: post #30
zecken wrote: post #26

Earlier quoted context omitted.

It seems like the opposite might be true, and that batteries degrade from cycle count and not because of time. This is why they are rated in cycle counts (i.e. cycles until 80% capacity = life time of battery). Also important is the charge/discharge rate, but because the batteries are so oversized in Teslas they can discharge as low as .25C even at highway speeds which helps increase their lifetime. source: http://ba…

They are rated in cycles so consumers do not need a degree in physics to understand the reality. Feel free to inspect a REAL spec sheet for a LiPo battery from a manufacturer (I think ATL provides some online)

Can you provide links? You clearly feel we have never seen a "real" sheet, perhaps more hand holding is order. I would appreciate the experience and would not do it without the link.

Re: Tesla Model S battery degradation data

#36

Post by vvanders »

dmitrygr wrote: post #17
vvanders wrote: post #15

Earlier quoted context omitted.

Phone batteries do poorly because the SoC generates a ton of heat when used which gets dumped right on the battery pouch. It's the same reason that you see early Leaf cells die out in Arizona while Tesla's have held up to 100k+. Thermal management makes or breaks longevity.

yes... I said that...high temp is bad

Sure, but you lead with:

> not because of amount of use, but because of time

Which makes it seem like time is more important that heat.

Re: Tesla Model S battery degradation data

#38

Post by dom0 »

sorenjan wrote: post #33
TomMarius wrote: post #7

Average life of ICE vehicles can't be 266kkm, that's absurdly low. Most of people I know have bought vehicles with that mileage and used it for another 100kkm after that at some point in their life (think first/second car, second family car, etc.). It's important to know that especially in Central/Eastern Europe, you can never trust the car's odometer - even the cars I'm talking about had probably more than 350kkm wh…

I've never seen anyone put more than one kilo before the unit before.

Well Americans did (sometimes still do) use micro-micro, as in µµF.

Re: Tesla Model S battery degradation data

#39

Post by TomMarius »

IkmoIkmo wrote: post #25
TomMarius wrote: post #7

Average life of ICE vehicles can't be 266kkm, that's absurdly low. Most of people I know have bought vehicles with that mileage and used it for another 100kkm after that at some point in their life (think first/second car, second family car, etc.). It's important to know that especially in Central/Eastern Europe, you can never trust the car's odometer - even the cars I'm talking about had probably more than 350kkm wh…

> Average life of ICE vehicles can't be 266kkm, that's absurdly low. I'm not sure it is... I mean, in my country (Netherlands) the average car user drives 13k km per year, in very car heavy countries that's probably around 20k. But here it'd mean a car would last on average 20 years, that's not absurdly low by any standard.

OK, maybe I misunderstood. To me it seems like it's comparation of incomparable though - you can't fault the vehicle that you didn't use it enough to broke it and had its life ended just because of age. With proper care, the vehicle could go much farther than 500k km with no noticeable performance or range degradations - just like the heavily used Teslas.

Re: Tesla Model S battery degradation data

#40

Post by sqeaky »

seszett wrote: post #22
sqeaky wrote: post #10

Earlier quoted context omitted.

I have seen plenty of cars not make to 165_000 miles, those that do are often near the end of their life. Mine is beat and barely holding together and it is at 97_000 miles.

165 000 miles is 266 000 km, for the readers who might wonder. My car is at 350 000 km now, and I'm not planning on selling it anytime soon. It doesn't have any special problem, except for a malfunctioning electric window lifter on one side. It's only one data point of course.

What percentage of car owners do this?

There is some percentage of cars crashed in the first week. It only takes a few of these to cancel out the average of extreme outliers like your car.

For reference I have never seen an odometer with more than 200 000 on it before. Even most classic rebuilds I have seen like 69 Corvettes have some high 100K count on them, some event have reset odometers.

Post reply on HN