Tesla Model S battery degradation data • Hacker News Board

Re: Tesla Model S battery degradation data

#101

Post by wongarsu » Thu, Aug 31, 2017, 11:45 PM UTC

kbenson wrote: post #8

> The red fitted line has a slope above 60.000 km (say 40,000 miles) of 1% per 50.000 km (30,000 miles). I'm going to bring this up because I think it's both interesting, and sometimes it comes up on its own and detracts from the conversation with conjecture (and sometimes harsh assumptions) until covered adequately[1] - different countries have different conventions for whether they use a comma or period for a thous…

>but there's not really any standardization of this as far as I know

There is. Resolution 10 of the 22nd General Conference on Weight and Measures [1] (the body responsible for the SI system) forbids the use of comma ordot as thousands separator. Other institutions like NIST have followed suit, forbidding or at least recommending against it. The recommended approach is to use spaces as thousand separators (or ideally: thin, non-breaking spaces).

You are still seeing a lot of people do it wrong because the resolution is from 2003, and these things take decades to overcome entrenched preferences.

1: http://www.bipm.org/utils/en/pdf/Resol22CGPM-EN.pdf

Re: Tesla Model S battery degradation data

#102

Post by GuB-42 » Thu, Aug 31, 2017, 11:48 PM UTC

That's quite impressive. What I am wondering is why they do do well, barely losing 10% in 5 years, compared to phone or laptop batteries that last maybe 3 years on average. AFAIK, they use the same technology, in fact, I wouldn't be surprised if the same batch of cells end up partly in Teslas and partly in laptops.

Re: Tesla Model S battery degradation data

#103

Post by noir_lord » Thu, Aug 31, 2017, 11:49 PM UTC

JshWright wrote: post #54

dom0 wrote: post #46

Earlier quoted context omitted.

> human-centric temperature scale One point (100 °F ~ 37 °C) doesn't make a scale.

Heh, sorry, that was just a tongue-in-cheek joke, not a central point of my comment. 0 to 100 on the Fahrenheit scale is "Really Cold" to "Really Hot". 0 to 100 on the Celsius scale is "Kinda Cold" to "Unsurvivable Hot". When I say it's "human-centric" I mean that it maps well to the range of human comfort (Celsius is obviously vastly superior in just about every other use).

I'm not sure that the 0-100 thing matters that much.

I'm in the UK we switched to C for temperatures back when I was a kid (I still vaguely remember both been used on weather charts back when they stuck the things on by hand..), 0 is cold, 10C is brisk, 16C is perfect, 20C is warm, 30C is hot, 35C is "kill me now".

Re: Tesla Model S battery degradation data

#104

Post by [deleted] » Thu, Aug 31, 2017, 11:49 PM UTC

sqeaky wrote: post #40

seszett wrote: post #22

Earlier quoted context omitted.

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.

[deleted]

Re: Tesla Model S battery degradation data

#105

Post by askvictor » Thu, Aug 31, 2017, 11:49 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…

For about 16 hours a day, my phone is somewhere between 100% and 0% charge, probably around body temperature or a little higher.

For the remaining 8 hours, while I'm sleeping, it's at close to 100%; which is not ideal. I'd be curious how effective an overnight charging scheme would be that charges up to 40%, then holds it there until say 4 a.m. (or some other time based on the phone consumption, capacity and charger output) then charges up to 100% so that when you wake up it's fully charged.

Re: Tesla Model S battery degradation data

#106

Post by true_religion » Thu, Aug 31, 2017, 11:50 PM UTC

notlob wrote: post #76

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.

My 80s diesel Benz is barely broken in at 249k miles. It all depends on the car. Ironically, more modern cars will probably not last as long! I can rebuild just about anything on this car, electronics included (most complicated part is perhaps a common opamp). On modern cars, as soon as the advanced ICs (say an ECU) are NLA you’re SOL.

Nah, older cars which weren't made well, or maintained well are all sitting in a landfill right now.

It's only the few that were both made better, with no production flaws, and great maintenance that have lasted long enough for us to see then with 150k miles before being purchased today.

Re: Tesla Model S battery degradation data

#107

Post by sowbug » Thu, Aug 31, 2017, 11:51 PM UTC

redthrowaway wrote: post #64

>Want to buy a Tesla? Use my referral link! Man, this only needs to work once for it to easily outstrip all other forms of revenue a blog might generate.

The current referral program offers only non-monetary awards (toy car, fancy wheels, entry in contest to win car). Better than a poke in the eye, but not as good as cash.

Re: Tesla Model S battery degradation data

#108

Post by sapienthomo » Thu, Aug 31, 2017, 11:54 PM UTC

mikeash wrote: post #97

hwillis wrote: post #92

Earlier quoted context omitted.

That hasn't been true for a very long time. Tesla uses their own chemistry[1] and has put in extensive work improving it. One of the higher-profile changes was that they use 1-2% silicon (Musk mentioned this in a stockholder call), which panasonic still hasn't rolled out to the rest of their batteries. [1]: https://electrek.co/2017/05/04/tesla-battery-researcher-chem...

I think people get confused because it's widely (and correctly) reported that Tesla uses 18650 cells. The confusion is that people think that's a model number, but it's actually just a size and shape. It's literally 18x65mm and the 0 means it's round. It tells you nothing at all about what's inside the cylinder.

NCR18650B is a specific series of parts from Panasonic(/Sanyo). If you want literally the exact battery that Tesla uses in the S, call Panasonic and tell them you want a shipment of ten million NCR18650BF (the new one with the silicon anode. The identity of these parts has been confirmed multiple times by people tearing down the battery packs (where they get this kind of disposable income, we don't know) and comparing the size/weight/discharge characteristics of single cells.

The "advanced chemistry" that Tesla moved to after a year of S production was a SiO-doped anode, exactly the difference between the B and BF part numbers from Panasonic-Sanyo. The cells weigh a gram less. This makes the charge density appear higher when the denominator is in terms of mass.

Tesla has done a wonderful job of selling their brand and convincing people that their batteries are other than off-the-shelf technology. In reality the same chemistry is available to anyone who calls up Panasonic and orders a hundred million batteries.

Re: Tesla Model S battery degradation data

#109

Post by spullara » Thu, Aug 31, 2017, 11:56 PM UTC

GuB-42 wrote: post #102

That's quite impressive. What I am wondering is why they do do well, barely losing 10% in 5 years, compared to phone or laptop batteries that last maybe 3 years on average. AFAIK, they use the same technology, in fact, I wouldn't be surprised if the same batch of cells end up partly in Teslas and partly in laptops.

I believe this is due to the fact that by default Tesla recommends that you don't fully charge or discharge the battery if you don't need the range. For phones people charge them all the way everyday (or more) and often discharge them all the way.

Re: Tesla Model S battery degradation data

#110

Post by bri3d » Thu, Aug 31, 2017, 11:56 PM UTC

GuB-42 wrote: post #102

That's quite impressive. What I am wondering is why they do do well, barely losing 10% in 5 years, compared to phone or laptop batteries that last maybe 3 years on average. AFAIK, they use the same technology, in fact, I wouldn't be surprised if the same batch of cells end up partly in Teslas and partly in laptops.

Laptops charge fully, discharge fully, get hot, and spend most of their time fully charged. This is the worst possible combination for Lithium-Cobalt/polymer batteries. Tesla batteries are never fully charged or discharged, are often charged at a lower C rate, and are thermally managed. A laptop with a cooled battery that only charged from 15-90% and took 3 hours to charge would hold up quite well, but it would weigh a ton and you'd hate to use it.