Tesla Model S battery degradation data • Hacker News Board

Re: Tesla Model S battery degradation data

#21

Post by dmitrygr » Thu, Aug 31, 2017, 10:27 PM UTC

epistasis wrote: post #14

dmitrygr wrote: post #9

This is fundamentally flawed because lithium batteries mostly degrade not because of amount of use, but because of time (and their charge state and temperature during this time). No matter if used or not, they will lose capacity. The rate of capacity loss is mainly dependent of average charge (best is 40%, worst is 100%) and temperature (best is 5 degrees C, the higher the worse). (This is also why phone batteries fa…

Wow, I've never heard anybody say that before or model it that way before. Though these tests are evidence of that, it's definitely not a common belief. Before the Tesla data, what informed you?

I provided a citation. Feel free to google around to find more info. This is basically how everyone models LiPo and Li-Ion cells. Tesla only publishes marketingspeak (which makes sense - that makes them money). Look for actual science and you'll see

Re: Tesla Model S battery degradation data

#22

Post by seszett » Thu, Aug 31, 2017, 10:28 PM UTC

sqeaky wrote: post #10

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 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.

Re: Tesla Model S battery degradation data

#23

Post by [deleted] » Thu, Aug 31, 2017, 10:28 PM UTC

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.

[deleted]

Re: Tesla Model S battery degradation data

#24

Post by TomMarius » Thu, Aug 31, 2017, 10:28 PM UTC

sqeaky wrote: post #10

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 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.

Uhh... My own car has around 98k miles (165kkm) and I consider it pretty new.

Re: Tesla Model S battery degradation data

#25

Post by IkmoIkmo » Thu, Aug 31, 2017, 10:28 PM UTC

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.

Re: Tesla Model S battery degradation data

#26

Post by zecken » Thu, Aug 31, 2017, 10:29 PM UTC

dmitrygr wrote: post #9

This is fundamentally flawed because lithium batteries mostly degrade not because of amount of use, but because of time (and their charge state and temperature during this time). No matter if used or not, they will lose capacity. The rate of capacity loss is mainly dependent of average charge (best is 40%, worst is 100%) and temperature (best is 5 degrees C, the higher the worse). (This is also why phone batteries fa…

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://batteryuniversity.com/learn/article/what_causes_lithi...

Re: Tesla Model S battery degradation data

#27

Post by cperciva » Thu, Aug 31, 2017, 10:29 PM UTC

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 Tesla's battery technology could be used in laptops and phones?

Sure, if you want a laptop which you can only recharge once per week.

Laptops and phones go through charge cycles much faster than cars; I'm sure Tesla has tuned their designs to maximize performance in that usage environment.

Re: Tesla Model S battery degradation data

#28

Post by tertius » Thu, Aug 31, 2017, 10:30 PM UTC

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

To be fair for phones you focused on: 100% charge and pocket (body) heat.

You did mention 100% and temperature being the problem generally though...

Re: Tesla Model S battery degradation data

#29

Post by fweespeech » Thu, Aug 31, 2017, 10:30 PM UTC

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?

It's far less likely real technology and far more likely massively undersold capacity in a Tesla.

Laptop and phone batteries are physically close to heat sources + are used frequently to substantial degrees of discharge + frequency of charge cycles after substantial discharge.

Re: Tesla Model S battery degradation data

#30

Post by dmitrygr » Thu, Aug 31, 2017, 10:30 PM UTC

zecken wrote: post #26

dmitrygr wrote: post #9

This is fundamentally flawed because lithium batteries mostly degrade not because of amount of use, but because of time (and their charge state and temperature during this time). No matter if used or not, they will lose capacity. The rate of capacity loss is mainly dependent of average charge (best is 40%, worst is 100%) and temperature (best is 5 degrees C, the higher the worse). (This is also why phone batteries fa…

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)