19 ms·

Tesla Model S battery degradation data

267 points by dabeeeenster 9y ago

dmitrygr 9y ago
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 fare so badly: they are often near 100% charge at 36.6 C in your pocket) http://www.sciencedirect.com/science/article/pii/S0378775316316998 http://www.sciencedirect.com/science/article/pii/S0378775316...
- colechristensen 9y ago
  Lithium batteries lose charge with use as well. Also rate of charge/discharge. It's more complicated than just one thing.
- epistasis 9y ago
  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?
  - JshWright 9y ago
    In the RC world, the '50/50' rule of thumb is common for lithium battery storage. 50% charge at 50˚F. It's close enough to the 'ideal' values, and easy to remember (for those of us used to a human-centric temperature scale)
    - dom0 9y ago
      > human-centric temperature scale One point (100 °F ~ 37 °C) doesn't make a scale.
      - JshWright 9y ago
        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).
        noir_lord 9y ago
        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".
        wongarsu 9y ago
        I'm not so sure I would call 100° C "unsurvivable". People go in saunas with 100° C all the time for enjoyment. If the air is dry enough, it's not that hot. Maybe it's unsustainable, you can't survive that indefinitely. But you can't survive 0° F indefinitely either, unless we bring protective clothing into the game.
        sureshv 9y ago
        100C would send you to the burn unit. I think you mean 100F. Edit: 100C is boiling point for water - is the ambient temp of the Sauna 100C?
        wongarsu 9y ago
        I'm thinking of finnish-style saunas, which operate at 60 to 100 °C [1] (with 100°C being a frequent option). You usually stay in them 10-15 min at a time, but I guess if you keep hydrated you could stay a lot longer. Finnish saunas are kept very dry. Sufficiently dry air makes very hot temperatures bearable because evaporation cooling from sweat gets more effective the dryer the surrounding air is. Water on the other hand makes sweating useless, which is why you can't tolerate water temperatures above body temperature (depending on how much of you is submerged). 1: https://en.wikipedia.org/wiki/Finnish_sauna#Types_of_sauna https://en.wikipedia.org/wiki/Finnish_sauna#Types_of_sauna
  - dmitrygr 9y ago
    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
    - epistasis 9y ago
      Weird, was that there when I replied? I definitely don't remember seeing it there... Perhaps I was just rushed. In any case thanks for the source!
- vvanders 9y ago
  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.
  - dmitrygr 9y ago
    yes... I said that...high temp is bad
    - tertius 9y ago
      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...
    - vvanders 9y ago
      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.
      - dmitrygr 9y ago
        heat != use think of it more as BADNESS = integral(abs(temp - 5), over time) * integral(abs(charge_amt - 40%), over time)
        vvanders 9y ago
        heat = (discharge + charge) use = (discharge + charge) hence: heat = use ;)
- zecken 9y ago
  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_lithium_ion_to_die http://batteryuniversity.com/learn/article/what_causes_lithi...
  - dmitrygr 9y ago
    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)
    - sqeaky 9y ago
      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.
      - dmitrygr 9y ago
        I am trying to find some non-NDA specs online for you. I saw this when I was working with these for a job and the specsheet was NDA (and I no longer work at the place this was)
      - deelowe 9y ago
        Here's a "real" manufacturer datasheet. The spec the battery life in cycles. Op may be correct, I don't know battery chemistry, but I've never seen batteries spec'ed the way the op describes in any "real" datasheets I've read. http://www.omnitron.cz/download/datasheet/NCR-18650PF.pdf http://www.omnitron.cz/download/datasheet/NCR-18650PF.pdf
- hwillis 9y ago
  They have a chart for calendar degradation. It's not weighted by mileage, but there are none of the datapoints you'd expect for that proposition (low miles, high age, high degradation).
- philipkglass 9y ago
  I do not believe that the passage of time is the main cause of lithium ion battery degradation. The source that you linked, http://www.sciencedirect.com/science/article/pii/S0378775316316998 http://www.sciencedirect.com/science/article/pii/S0378775316..., does not seem to support that idea either. Figure 3 from the paper, "Cause and effect of degradation mechanisms and associated degradation modes," shows time as just one of 8 degradation mechanisms affecting lithium ion batteries. Other figures/tables from the paper do not emphasize time as the primary degradation mechanism, nor does the body text. Nor is there any explicit passage-of-time term in the final diagnostic model that the authors develop.
- WillPostForFood 9y ago
  So if you were optimizing your phone for low battery degradation, when would you charge it, and to what %? If you were trying to keep it around 40%, would a good strategy be to let drop to 20%, and then only charge to 60%, or would you bias it even lower to keep it away from 100%, like a working range of 10-50%?
  - skykooler 9y ago
    The ideal state of charge for a lithium battery is 50%. So charging between 20% and 80% would significantly lengthen battery life. If you wanted to completely optimize for low battery degradation you'd charge between like 49% and 51% and only have a few minutes of usage, but that kind of defeats the point of keeping a lot of battery capacity.
  - jandrese 9y ago
    Maybe schedule it like so: Between 6AM and 8AM: Charge to 100% All other times: Charge to 75% So the battery is topped off in the morning right before you put it in your pocket for the day, but otherwise doesn't fully charge to save the cell life.
- askvictor 9y ago
  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.
- onetwotree 9y ago
  I've recently had to become pretty familiar with this subject for work, and your comment is only partially correct. Li-Ion battery degradation is generally modeled as two (roughly additive) components, called calendar and cycle aging. Calendar aging is what you're talking about in your comment - it's basically determined by the temperature and state of charge. Both of these impact the rate of chemical processes that lead to loss of lithium and active material. This is what happens when the battery is sitting on the shelf. Cycle aging, on the other hand, happens when you charge or discharge the battery and is driven mostly by the actual volume change in the anode and cathode when they get lithiated (it's quite significant, up to 15% or so in some materials). This introduces mechanical stress, which can break the protective film that forms between the electrodes and electrolyte and allow chemical degradation to proceed at a faster rate. The degree of mechanical stress is mostly determined by the depth of discharge, although rate of charge and discharge is also believed to be important. Cycle degradation is also impacted by the temperature at which the battery is cycled, in a similar way to calendar aging. With high temperature variance (low temperatures will wreck your batteries too, and I can't recommend keeping them at 5C), calendar aging is the dominant mode. This is absolutely the case with cell phone batteries. However, electric vehicles, especially higher end ones like the Tesla, have an active cooling system that keeps the battery at a constant temperature, even when the car is "off". This is why many EVB warranties will be voided if you let them run out of charge for more than 14 days - at that point, the cooling system isn't working and your poor battery is at the mercy of the elements. Under closely controlled temperatures, cycle aging is the most important factor, and it's dominated by depth of discharge. If you drain the battery as far as it will allow you every day, it's going to be hosed. If you only go down to about 80% of the allowed charge every other day, it'll last for quite a while. These numbers are roughly correlated, obviously, with the mileage on the car, but the relationship is not simple, and I'd caution against considering mileage to be a good determinant of battery degradation. Some good sources if you want to learn more: A fairly simple model of degradation (ignores charge/discharge rate): https://www.researchgate.net/publication/303890624_Modeling_of_Lithium-Ion_Battery_Degradation_for_Cell_Life_Assessment https://www.researchgate.net/publication/303890624_Modeling_... A thesis on the subject, goes into great detail and has an excellent bibliography: http://webfiles.portal.chalmers.se/et/Lic/JensGroot.pdf http://webfiles.portal.chalmers.se/et/Lic/JensGroot.pdf
mschuster91 9y ago
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.
- RachelF 9y ago
  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?
  - mschuster91 9y ago
    You can replicate it to a certain extent by not discharging below 10-20% (don't know the exact range though). Limiting upper bound is likely either impossible or requires reprogramming the battery control unit. What is also an advantage: Teslas can cool (and I believe also heat) the batteries so they don't enter temperature ranges where degradation is accelerated. In a laptop and certainly a phone there is neither space nor weight available for a thermal management.
    - Zekio 9y ago
      Pretty sure all newer thinkpads can be configured to only charge to a threshold
  - cperciva 9y ago
    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.
  - fweespeech 9y ago
    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.
obblekk 9y ago
Is there a non-linear decline at the end? i.e. do the batteries at some point just give up and capacity starts declining very quickly?
- tinus_hn 9y ago
  In the comments it is explained that this is because there is only one user who made it that far so the graph is skewed towards that users data. That users battery happened to be slightly worse than the mean so the graph goes down. It doesn't really mean anything.
- hwillis 9y ago
  No, loss slows down over time and continues to drop approximately linearly. The batteries develop a protective effect as they degrade, which slows further loss.
TomMarius 9y ago
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 when bought.
- sqeaky 9y ago
  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.
  - vvanders 9y ago
    Yup, when I donated my car at 145k mi I expected to to be resold but got notified that it was turned into parts for $350(they had to report back to me for tax reasons).
  - dom0 9y ago
    97 000 miles, just barely 160k kilometers. That's... really not much at all.
  - seszett 9y ago
    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.
    - sqeaky 9y ago
      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.
kbenson 9y ago
> 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 thousands separator, and in those languages if they also speak in English sometimes, they may choose to continue using a period as a thousands separator as is convention in their country, even if the predominant language in their country is not English, and there are circumstances which might make that more common for some people.[2] In this case, we have what appears to be switching convention when switching unit systems, which is interesting. I'm not sure if it's more or less confusing in the end, but there's not really any standardization of this as far as I know, so it's all good. 1: https://news.ycombinator.com/item?id=14970002 https://news.ycombinator.com/item?id=14970002 2: https://news.ycombinator.com/item?id=14862695 https://news.ycombinator.com/item?id=14862695
- microcolonel 9y ago
  Frankly it might be a bit confusing to Canadians, here we use the U.S. numeric conventions, but we tend to use a mix of SI and imperial units, and in this case we'd use kilometres for ground distance, with thousands separated by commas. The UK also seems to prefer commas to separate thousands. I'm inoculated against confusion about this because I've done a lot of software and content localization, and have a grasp on the specifics for a lot of different cultures. I think the problem is exacerbated by the underuse of the SI system's prefixes. Why even talk about thousands of kilometres when you can speak in tens of megametres? Added: I figure it's getting to the point where there are too many genuine English locales to keep up. It takes a lot of energy for normal people to retain fluency in dialects and locales like en_US, en_IN, en_CA (thankfully rapidly merging with en_US), en_GB, en_AU, en_JM, en_MY, etc. etc. etc.. all at the same time. Maybe at some point there will be a great and natural convergence.
  - photojosh 9y ago
    > Why even talk about thousands of kilometres when you can speak in tens of megametres? Probably because when you're speaking about them colloquially, you don't say "kilometres" you say "kays". That probably varies by locale too, I'm in en_AU. How is it over your way? I do like the nerdiness in the idea of saying "two megs" instead of "two thousand kays", but it's never going to happen.
rodgerd 9y ago
Presenting the Telsa graph with the full x axis (to demonstrate the rate of degradation is very small), and then the Leaf with a reduced x axis (to suggest it's got serious problems) doesn't really lend confidence.
peterwwillis 9y ago
FYI: Tesla batteries are literally laptop batteries with cell balancing. No secret battery magic going on. You could in theory crack open the pack and replace inefficient cells to get your capacity back. But, I'm assuming this is too huge a PITA for most people.
- sapienthomo 9y ago
  The "technology" involved here is #1 understating the raw capacity of the battery and #2 managing the charge/discharge levels and rates to maintain that capacity. This gives a good user experience and perception of longevity. Apple does the same thing with the iPhone and it makes the iPhone user experience noticeably better than comparable Android handsets where the charge controller just charges the battery as high and as fast as it can. Essentially, this is good UX, but for battery charge indicators.
  - majormajor 9y ago
    > Apple does the same thing with the iPhone and it makes the iPhone user experience noticeably better than comparable Android handsets where the charge controller just charges the battery as high and as fast as it can. iPhone battery life and lifespan has been a much-hyped thing in certain circles for a while, so back when I got my first iPhone 5S, imagine my dismay to discover it was actually not noticeably different than my old HTC. Same with the 6.
    - sapienthomo 9y ago
      What exact models are we comparing? HTC's current phones weigh more than the iPhone 6 and much more than the iPhone 5s. Note also that since Android follows the Windows/PC model, there exists hardware that does this correctly, and there exists hardware that does it incorrectly.
- maratd 9y ago
  > No secret battery magic going on. They have a complex cooling system. Your laptop battery definitely doesn't have that. If it did, it wouldn't need to be replaced every few years.
hwillis 9y ago
You lose about 5% capacity in the first 45k miles, then it's essentially flat- 3% in 120k miles. It seems like keeping your charge level at 100% has some impact on lifetime, but lower than 90% looks to have very limited returns. I'll be interested to see how the cycle graph evolves, but right now it looks like batteries will on average make it to 2500-3000 cycles, which is great. There are a number of early outliers that had more significant capacity loss. They're all from the US- Europe & Asia have over 800 reports compared to 170 in the US, but the lowest reading there is 88% compared to 85% in the US. All with ~<35k miles, <4 years old, mostly 60 kWh models. I'm not quite ready to call fake, but the numbers from the US are definitely unlike other countries. Those cars weren't driven nearly as hard as their counterparts in other countries. The only real explanation other than false reporting is heat, but unfortunately there is no indication of location besides one guy in Michigan. Keep that in mind when looking at all the graphs- the lowest data points are almost exclusively very strange outliers from the US that weren't driven particularly hard.
- ProfessorLayton 9y ago
  IIRC no high voltage car batteries are actually charged/discharged 0-100%, even if it reads so from the user's perspective. This is due to significantly increased wear on the batteries when fully charged/discharged, and why a cellphone battery only lasts a few years. The batteries need to be significantly over-provisioned to extend their lifespan. A Prius, for example, will keep the battery's SOC between 40-80%, and is one of the most reliable hybrids out there. The same is true for EVs, so charging it till it reads 100% does not mean the battery is at capacity. The same is true when it reads empty.
  - mikeash 9y ago
    I don't think any lithium ion battery is ever truly used at 0-100%. True 100% would be just before it explodes, and true 0% would be just before it completely bricks. You get horrible degradation near those areas so they're always avoided. I'm sure consumer electronics push it farther than cars do, though.
  - hwillis 9y ago
RoboTeddy 9y ago
Battery science is fascinating. Here's in an-depth look at degredation: https://www.youtube.com/watch?v=9qi03QawZEk https://www.youtube.com/watch?v=9qi03QawZEk The speaker (Jeff Dahn -- he now works with Tesla) pioneered a faster way to tell how fast a battery will degrade (which means you can iterate your design faster!)
redthrowaway 9y ago
>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.
- sowbug 9y ago
  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.
  - incompatible 9y ago
    There's not much point in Tesla offering a lot. A search for "Tesla" in Google gets you to the right place to buy one with a couple of clicks.
bunkydoo 9y ago
I'm just over here patiently awaiting some startup to unseat Tesla as the king of speedy, luxury, electric automotive. Nobody is quite taking the cake, or even trying for that matter.
- hwillis 9y ago
  There are at least a dozen companies trying to do exactly that. Thing is, Tesla was exceptionally lucky, and it is still incredibly hard to build a car company. Tesla managed to squeak through to the Model S, which was absolutely critical. For companies that are trying to make a Tesla killer, they have to hit the price point above a Model S with zero volume. That's means no factory and hand building almost everything. That destroys any ability to price reasonably. Tesla killers start at 300k and range up to 2 million. Nobody at that price point wants electric cars right now, or at least very few people. It doesn't come with the same bragging rights as a Ferrari or Koenigsegg. Those have brand and absolute, vastly supreme performance respectively. Also, I suspect people are aware that as soon as Tesla announces a new roadster the game will be over. Nobody will want to buy anything else.
GuB-42 9y ago
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.
- spullara 9y ago
  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.
  - heydonovan 9y ago
    How can we prevent a battery from fulling charging? We plug a car/phone in at night, and wake up to it 100% charged.
    - monitron 9y ago
      Tesla's cars have a charge limit you can set, after which the car simply stops. I believe they come by default at 90%. You're supposed to override it if you want to go on a long road trip. Would be cool if there was a similar feature available on phones. Maybe you could rig up something with Tasker or the like on an Android.
      - kalleboo 9y ago
        It looks like Sony's Android phones have this option https://www.phonearena.com/news/Sony-Xperia-Marshmallow-update-beta-includes-soft-charging-allowing-the-battery-to-live-longer_id82551 https://www.phonearena.com/news/Sony-Xperia-Marshmallow-upda...
      - taheca 9y ago
        Interesting fact.. with the last software update they changed what was considered trip, and local pretty significantly. I wonder if that is aligned to a SW improvement in battery management?
11thEarlOfMar 9y ago
This is pretty surprising. What it means is that most owners will not need to replace their batteries in the time that they own the car. In my 'total cost of ownership' models, I've assumed a battery replacement at 100,000 miles, but that appears to not be necessary. This changes the calculation considerably. Not to mention that if the drive train can go 400,000 miles without needing major repair, I can keep the car 2x as long as an ICE, further reducing the cost of owning an electric vehicle.
- toomuchtodo 9y ago
  Musk has made a comment on an investor call that they're targeting a million mile lifespan for the motor.
  - dalbasal 9y ago
    I think ICE cars are just not optimized for prolonged life. Many countries have policies discouraging long lifespans, more than ever since emmissions laws. Also, EOL for a car is several owners and 5-10 years removed from first purchase. This adds up to a realtiy where doubling the expected lifespan is not worth much more, in sales. Basically, if Tesla want to make this a goal then beating benchmarks should be relatively easy.
    - dsfyu404ed 9y ago
      x2. Modern vehicles have a targeted minimum lifetime based on certain usage models. That's why people who are driving a pickup truck around all day for work with a few hundred pounds of equipment (e.g. medical equipment service technician) get 500k+ out of them and oil field trucks are beat before 100k.
- compute_me 9y ago
  check this out: http://www.tesloop.com/blog/2017/8/30/tesla-model-s-hits-300k-miles-with-less-than-11k-maintenance-costs http://www.tesloop.com/blog/2017/8/30/tesla-model-s-hits-300...
amgin3 9y ago
If it were the same quality as my laptop battery, you would have to keep it plugged in while driving after 1 year.
lafar6502 9y ago
What all these dots above 100% mean, besides moving the average up? And I'd be worried about the owners of all these dots below the line
jakobegger 9y ago
Doesn‘t anybody find it curious that the source of data are range estimates displayed on the cars built-in dashboard? For all we know, Teslas might be programmed to show more „optimistic“ estimates as the batteries get older. I‘m not saying this is actually the case, but these stats are effectively manufacturer-provided numbers. Would you trust data like this if it came from any other car manufacturer? If you have a gasoline car, do you trust the fuel consumption rate displayed on the dashboard? Should journalists trust it? Or should they measure how much gas they put in the tank and divide it by distance driven?
- mantas 9y ago
  I know it's anecdata, but I found the dashboard estimate on my VW (heh) strangely correct. It's off by +/- 5% in most cases. Since it doesn't take upcoming traffic/terrain/wind into account, I find it more than reasonable.
- gambiting 9y ago
  I trust the fuel consumption in my car, yeah. If it says I've been using 12l/100km on average and I've travelled 500km, you can bet I'm filling up exactly 60l at the pump.
  - dx034 9y ago
    That really depends on the car. I don't own a car so often use rental cars. Most cars' consumption is within 10% of the shown values but at least every fifth car I drive has vastly different numbers. I think it is not necessarily due to the car but because of the calculation methods they use. If you drive motorway and city, consumption is accurate. But as soon as you start driving in the mountains or a mix of different terrains, data often vastly differs.
    - nateguchi 9y ago
      If the car has a Mass Airflow Sensor (MAF), then it can more accurately calculate the fuel usage. The majority of older / cheaper cars use a Manifold Absolute Pressure Sensor (MAP) and have to make some guesses at what the actual fuel usage is.
friendzis 9y ago
There is one thing about batteries: Watt-hours battery will provide highly depend on current (electric current) draw. To some extent this also applies to deterioration. Which means that as batteries get more and more used, one should expect to see higher and higher disparity between range in sporty and economic driving. In other words as battery gets older, the higher consumption driving aggressively. Tesla, however, has one redeeming factor. While battery voltage-capacity@current curve will change over time, Tesla can collect real world usage data and with software updates push updated curves for older batteries to adjust range estimation models for battery wear.
iambateman 9y ago
Correct me if I'm wrong, but Lithium Ion batteries have exponential degradation, right? The data here assumes constant degradation, which is going to throw this off.
lafar6502 9y ago
So you can conclude your car willl be worth nothing after 200k miles

267 points by dabeeeenster 9y ago

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 fare so badly: they are often near 100% charge at 36.6 C in your pocket) http://www.sciencedirect.com/science/article/pii/S0378775316316998 http://www.sciencedirect.com/science/article/pii/S0378775316...

colechristensen 9y ago
Lithium batteries lose charge with use as well. Also rate of charge/discharge. It's more complicated than just one thing.
epistasis 9y ago
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?
- JshWright 9y ago
  In the RC world, the '50/50' rule of thumb is common for lithium battery storage. 50% charge at 50˚F. It's close enough to the 'ideal' values, and easy to remember (for those of us used to a human-centric temperature scale)
  - dom0 9y ago
    > human-centric temperature scale One point (100 °F ~ 37 °C) doesn't make a scale.
    - JshWright 9y ago
      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).
      - noir_lord 9y ago
        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".
      - wongarsu 9y ago
        I'm not so sure I would call 100° C "unsurvivable". People go in saunas with 100° C all the time for enjoyment. If the air is dry enough, it's not that hot. Maybe it's unsustainable, you can't survive that indefinitely. But you can't survive 0° F indefinitely either, unless we bring protective clothing into the game.
        sureshv 9y ago
        100C would send you to the burn unit. I think you mean 100F. Edit: 100C is boiling point for water - is the ambient temp of the Sauna 100C?
        wongarsu 9y ago
        I'm thinking of finnish-style saunas, which operate at 60 to 100 °C [1] (with 100°C being a frequent option). You usually stay in them 10-15 min at a time, but I guess if you keep hydrated you could stay a lot longer. Finnish saunas are kept very dry. Sufficiently dry air makes very hot temperatures bearable because evaporation cooling from sweat gets more effective the dryer the surrounding air is. Water on the other hand makes sweating useless, which is why you can't tolerate water temperatures above body temperature (depending on how much of you is submerged). 1: https://en.wikipedia.org/wiki/Finnish_sauna#Types_of_sauna https://en.wikipedia.org/wiki/Finnish_sauna#Types_of_sauna
- dmitrygr 9y ago
  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
  - epistasis 9y ago
    Weird, was that there when I replied? I definitely don't remember seeing it there... Perhaps I was just rushed. In any case thanks for the source!
vvanders 9y ago
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.
- dmitrygr 9y ago
  yes... I said that...high temp is bad
  - tertius 9y ago
    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...
  - vvanders 9y ago
    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.
    - dmitrygr 9y ago
      heat != use think of it more as BADNESS = integral(abs(temp - 5), over time) * integral(abs(charge_amt - 40%), over time)
      - vvanders 9y ago
        heat = (discharge + charge) use = (discharge + charge) hence: heat = use ;)
zecken 9y ago
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_lithium_ion_to_die http://batteryuniversity.com/learn/article/what_causes_lithi...
- dmitrygr 9y ago
  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)
  - sqeaky 9y ago
    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.
    - dmitrygr 9y ago
      I am trying to find some non-NDA specs online for you. I saw this when I was working with these for a job and the specsheet was NDA (and I no longer work at the place this was)
    - deelowe 9y ago
      Here's a "real" manufacturer datasheet. The spec the battery life in cycles. Op may be correct, I don't know battery chemistry, but I've never seen batteries spec'ed the way the op describes in any "real" datasheets I've read. http://www.omnitron.cz/download/datasheet/NCR-18650PF.pdf http://www.omnitron.cz/download/datasheet/NCR-18650PF.pdf
hwillis 9y ago
They have a chart for calendar degradation. It's not weighted by mileage, but there are none of the datapoints you'd expect for that proposition (low miles, high age, high degradation).
philipkglass 9y ago
I do not believe that the passage of time is the main cause of lithium ion battery degradation. The source that you linked, http://www.sciencedirect.com/science/article/pii/S0378775316316998 http://www.sciencedirect.com/science/article/pii/S0378775316..., does not seem to support that idea either. Figure 3 from the paper, "Cause and effect of degradation mechanisms and associated degradation modes," shows time as just one of 8 degradation mechanisms affecting lithium ion batteries. Other figures/tables from the paper do not emphasize time as the primary degradation mechanism, nor does the body text. Nor is there any explicit passage-of-time term in the final diagnostic model that the authors develop.
WillPostForFood 9y ago
So if you were optimizing your phone for low battery degradation, when would you charge it, and to what %? If you were trying to keep it around 40%, would a good strategy be to let drop to 20%, and then only charge to 60%, or would you bias it even lower to keep it away from 100%, like a working range of 10-50%?
- skykooler 9y ago
  The ideal state of charge for a lithium battery is 50%. So charging between 20% and 80% would significantly lengthen battery life. If you wanted to completely optimize for low battery degradation you'd charge between like 49% and 51% and only have a few minutes of usage, but that kind of defeats the point of keeping a lot of battery capacity.
- jandrese 9y ago
  Maybe schedule it like so: Between 6AM and 8AM: Charge to 100% All other times: Charge to 75% So the battery is topped off in the morning right before you put it in your pocket for the day, but otherwise doesn't fully charge to save the cell life.
askvictor 9y ago
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.
onetwotree 9y ago
I've recently had to become pretty familiar with this subject for work, and your comment is only partially correct. Li-Ion battery degradation is generally modeled as two (roughly additive) components, called calendar and cycle aging. Calendar aging is what you're talking about in your comment - it's basically determined by the temperature and state of charge. Both of these impact the rate of chemical processes that lead to loss of lithium and active material. This is what happens when the battery is sitting on the shelf. Cycle aging, on the other hand, happens when you charge or discharge the battery and is driven mostly by the actual volume change in the anode and cathode when they get lithiated (it's quite significant, up to 15% or so in some materials). This introduces mechanical stress, which can break the protective film that forms between the electrodes and electrolyte and allow chemical degradation to proceed at a faster rate. The degree of mechanical stress is mostly determined by the depth of discharge, although rate of charge and discharge is also believed to be important. Cycle degradation is also impacted by the temperature at which the battery is cycled, in a similar way to calendar aging. With high temperature variance (low temperatures will wreck your batteries too, and I can't recommend keeping them at 5C), calendar aging is the dominant mode. This is absolutely the case with cell phone batteries. However, electric vehicles, especially higher end ones like the Tesla, have an active cooling system that keeps the battery at a constant temperature, even when the car is "off". This is why many EVB warranties will be voided if you let them run out of charge for more than 14 days - at that point, the cooling system isn't working and your poor battery is at the mercy of the elements. Under closely controlled temperatures, cycle aging is the most important factor, and it's dominated by depth of discharge. If you drain the battery as far as it will allow you every day, it's going to be hosed. If you only go down to about 80% of the allowed charge every other day, it'll last for quite a while. These numbers are roughly correlated, obviously, with the mileage on the car, but the relationship is not simple, and I'd caution against considering mileage to be a good determinant of battery degradation. Some good sources if you want to learn more: A fairly simple model of degradation (ignores charge/discharge rate): https://www.researchgate.net/publication/303890624_Modeling_of_Lithium-Ion_Battery_Degradation_for_Cell_Life_Assessment https://www.researchgate.net/publication/303890624_Modeling_... A thesis on the subject, goes into great detail and has an excellent bibliography: http://webfiles.portal.chalmers.se/et/Lic/JensGroot.pdf http://webfiles.portal.chalmers.se/et/Lic/JensGroot.pdf

mschuster91 9y ago

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.

RachelF 9y ago
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?
- mschuster91 9y ago
  You can replicate it to a certain extent by not discharging below 10-20% (don't know the exact range though). Limiting upper bound is likely either impossible or requires reprogramming the battery control unit. What is also an advantage: Teslas can cool (and I believe also heat) the batteries so they don't enter temperature ranges where degradation is accelerated. In a laptop and certainly a phone there is neither space nor weight available for a thermal management.
  - Zekio 9y ago
    Pretty sure all newer thinkpads can be configured to only charge to a threshold
- cperciva 9y ago
  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.
- fweespeech 9y ago
  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.

obblekk 9y ago

Is there a non-linear decline at the end? i.e. do the batteries at some point just give up and capacity starts declining very quickly?

tinus_hn 9y ago
In the comments it is explained that this is because there is only one user who made it that far so the graph is skewed towards that users data. That users battery happened to be slightly worse than the mean so the graph goes down. It doesn't really mean anything.
hwillis 9y ago
No, loss slows down over time and continues to drop approximately linearly. The batteries develop a protective effect as they degrade, which slows further loss.

TomMarius 9y ago

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 when bought.

sqeaky 9y ago
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.
- vvanders 9y ago
  Yup, when I donated my car at 145k mi I expected to to be resold but got notified that it was turned into parts for $350(they had to report back to me for tax reasons).
- dom0 9y ago
  97 000 miles, just barely 160k kilometers. That's... really not much at all.
- seszett 9y ago
  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.
  - sqeaky 9y ago
    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.

kbenson 9y ago

> 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 thousands separator, and in those languages if they also speak in English sometimes, they may choose to continue using a period as a thousands separator as is convention in their country, even if the predominant language in their country is not English, and there are circumstances which might make that more common for some people.[2] In this case, we have what appears to be switching convention when switching unit systems, which is interesting. I'm not sure if it's more or less confusing in the end, but there's not really any standardization of this as far as I know, so it's all good. 1: https://news.ycombinator.com/item?id=14970002 https://news.ycombinator.com/item?id=14970002 2: https://news.ycombinator.com/item?id=14862695 https://news.ycombinator.com/item?id=14862695

microcolonel 9y ago
Frankly it might be a bit confusing to Canadians, here we use the U.S. numeric conventions, but we tend to use a mix of SI and imperial units, and in this case we'd use kilometres for ground distance, with thousands separated by commas. The UK also seems to prefer commas to separate thousands. I'm inoculated against confusion about this because I've done a lot of software and content localization, and have a grasp on the specifics for a lot of different cultures. I think the problem is exacerbated by the underuse of the SI system's prefixes. Why even talk about thousands of kilometres when you can speak in tens of megametres? Added: I figure it's getting to the point where there are too many genuine English locales to keep up. It takes a lot of energy for normal people to retain fluency in dialects and locales like en_US, en_IN, en_CA (thankfully rapidly merging with en_US), en_GB, en_AU, en_JM, en_MY, etc. etc. etc.. all at the same time. Maybe at some point there will be a great and natural convergence.
- photojosh 9y ago
  > Why even talk about thousands of kilometres when you can speak in tens of megametres? Probably because when you're speaking about them colloquially, you don't say "kilometres" you say "kays". That probably varies by locale too, I'm in en_AU. How is it over your way? I do like the nerdiness in the idea of saying "two megs" instead of "two thousand kays", but it's never going to happen.

rodgerd 9y ago

Presenting the Telsa graph with the full x axis (to demonstrate the rate of degradation is very small), and then the Leaf with a reduced x axis (to suggest it's got serious problems) doesn't really lend confidence.

peterwwillis 9y ago

FYI: Tesla batteries are literally laptop batteries with cell balancing. No secret battery magic going on. You could in theory crack open the pack and replace inefficient cells to get your capacity back. But, I'm assuming this is too huge a PITA for most people.

sapienthomo 9y ago
The "technology" involved here is #1 understating the raw capacity of the battery and #2 managing the charge/discharge levels and rates to maintain that capacity. This gives a good user experience and perception of longevity. Apple does the same thing with the iPhone and it makes the iPhone user experience noticeably better than comparable Android handsets where the charge controller just charges the battery as high and as fast as it can. Essentially, this is good UX, but for battery charge indicators.
- majormajor 9y ago
  > Apple does the same thing with the iPhone and it makes the iPhone user experience noticeably better than comparable Android handsets where the charge controller just charges the battery as high and as fast as it can. iPhone battery life and lifespan has been a much-hyped thing in certain circles for a while, so back when I got my first iPhone 5S, imagine my dismay to discover it was actually not noticeably different than my old HTC. Same with the 6.
  - sapienthomo 9y ago
    What exact models are we comparing? HTC's current phones weigh more than the iPhone 6 and much more than the iPhone 5s. Note also that since Android follows the Windows/PC model, there exists hardware that does this correctly, and there exists hardware that does it incorrectly.
maratd 9y ago
> No secret battery magic going on. They have a complex cooling system. Your laptop battery definitely doesn't have that. If it did, it wouldn't need to be replaced every few years.

hwillis 9y ago

You lose about 5% capacity in the first 45k miles, then it's essentially flat- 3% in 120k miles. It seems like keeping your charge level at 100% has some impact on lifetime, but lower than 90% looks to have very limited returns. I'll be interested to see how the cycle graph evolves, but right now it looks like batteries will on average make it to 2500-3000 cycles, which is great. There are a number of early outliers that had more significant capacity loss. They're all from the US- Europe & Asia have over 800 reports compared to 170 in the US, but the lowest reading there is 88% compared to 85% in the US. All with ~<35k miles, <4 years old, mostly 60 kWh models. I'm not quite ready to call fake, but the numbers from the US are definitely unlike other countries. Those cars weren't driven nearly as hard as their counterparts in other countries. The only real explanation other than false reporting is heat, but unfortunately there is no indication of location besides one guy in Michigan. Keep that in mind when looking at all the graphs- the lowest data points are almost exclusively very strange outliers from the US that weren't driven particularly hard.

ProfessorLayton 9y ago
IIRC no high voltage car batteries are actually charged/discharged 0-100%, even if it reads so from the user's perspective. This is due to significantly increased wear on the batteries when fully charged/discharged, and why a cellphone battery only lasts a few years. The batteries need to be significantly over-provisioned to extend their lifespan. A Prius, for example, will keep the battery's SOC between 40-80%, and is one of the most reliable hybrids out there. The same is true for EVs, so charging it till it reads 100% does not mean the battery is at capacity. The same is true when it reads empty.
- mikeash 9y ago
  I don't think any lithium ion battery is ever truly used at 0-100%. True 100% would be just before it explodes, and true 0% would be just before it completely bricks. You get horrible degradation near those areas so they're always avoided. I'm sure consumer electronics push it farther than cars do, though.
- hwillis 9y ago

RoboTeddy 9y ago

Battery science is fascinating. Here's in an-depth look at degredation: https://www.youtube.com/watch?v=9qi03QawZEk https://www.youtube.com/watch?v=9qi03QawZEk The speaker (Jeff Dahn -- he now works with Tesla) pioneered a faster way to tell how fast a battery will degrade (which means you can iterate your design faster!)

redthrowaway 9y ago

>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.

sowbug 9y ago
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.
- incompatible 9y ago
  There's not much point in Tesla offering a lot. A search for "Tesla" in Google gets you to the right place to buy one with a couple of clicks.

bunkydoo 9y ago

I'm just over here patiently awaiting some startup to unseat Tesla as the king of speedy, luxury, electric automotive. Nobody is quite taking the cake, or even trying for that matter.

hwillis 9y ago
There are at least a dozen companies trying to do exactly that. Thing is, Tesla was exceptionally lucky, and it is still incredibly hard to build a car company. Tesla managed to squeak through to the Model S, which was absolutely critical. For companies that are trying to make a Tesla killer, they have to hit the price point above a Model S with zero volume. That's means no factory and hand building almost everything. That destroys any ability to price reasonably. Tesla killers start at 300k and range up to 2 million. Nobody at that price point wants electric cars right now, or at least very few people. It doesn't come with the same bragging rights as a Ferrari or Koenigsegg. Those have brand and absolute, vastly supreme performance respectively. Also, I suspect people are aware that as soon as Tesla announces a new roadster the game will be over. Nobody will want to buy anything else.

GuB-42 9y ago

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.

spullara 9y ago
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.
- heydonovan 9y ago
  How can we prevent a battery from fulling charging? We plug a car/phone in at night, and wake up to it 100% charged.
  - monitron 9y ago
    Tesla's cars have a charge limit you can set, after which the car simply stops. I believe they come by default at 90%. You're supposed to override it if you want to go on a long road trip. Would be cool if there was a similar feature available on phones. Maybe you could rig up something with Tasker or the like on an Android.
    - kalleboo 9y ago
      It looks like Sony's Android phones have this option https://www.phonearena.com/news/Sony-Xperia-Marshmallow-update-beta-includes-soft-charging-allowing-the-battery-to-live-longer_id82551 https://www.phonearena.com/news/Sony-Xperia-Marshmallow-upda...
    - taheca 9y ago
      Interesting fact.. with the last software update they changed what was considered trip, and local pretty significantly. I wonder if that is aligned to a SW improvement in battery management?

11thEarlOfMar 9y ago

This is pretty surprising. What it means is that most owners will not need to replace their batteries in the time that they own the car. In my 'total cost of ownership' models, I've assumed a battery replacement at 100,000 miles, but that appears to not be necessary. This changes the calculation considerably. Not to mention that if the drive train can go 400,000 miles without needing major repair, I can keep the car 2x as long as an ICE, further reducing the cost of owning an electric vehicle.

toomuchtodo 9y ago
Musk has made a comment on an investor call that they're targeting a million mile lifespan for the motor.
- dalbasal 9y ago
  I think ICE cars are just not optimized for prolonged life. Many countries have policies discouraging long lifespans, more than ever since emmissions laws. Also, EOL for a car is several owners and 5-10 years removed from first purchase. This adds up to a realtiy where doubling the expected lifespan is not worth much more, in sales. Basically, if Tesla want to make this a goal then beating benchmarks should be relatively easy.
  - dsfyu404ed 9y ago
    x2. Modern vehicles have a targeted minimum lifetime based on certain usage models. That's why people who are driving a pickup truck around all day for work with a few hundred pounds of equipment (e.g. medical equipment service technician) get 500k+ out of them and oil field trucks are beat before 100k.
compute_me 9y ago
check this out: http://www.tesloop.com/blog/2017/8/30/tesla-model-s-hits-300k-miles-with-less-than-11k-maintenance-costs http://www.tesloop.com/blog/2017/8/30/tesla-model-s-hits-300...

amgin3 9y ago

If it were the same quality as my laptop battery, you would have to keep it plugged in while driving after 1 year.

lafar6502 9y ago

What all these dots above 100% mean, besides moving the average up? And I'd be worried about the owners of all these dots below the line

jakobegger 9y ago

Doesn‘t anybody find it curious that the source of data are range estimates displayed on the cars built-in dashboard? For all we know, Teslas might be programmed to show more „optimistic“ estimates as the batteries get older. I‘m not saying this is actually the case, but these stats are effectively manufacturer-provided numbers. Would you trust data like this if it came from any other car manufacturer? If you have a gasoline car, do you trust the fuel consumption rate displayed on the dashboard? Should journalists trust it? Or should they measure how much gas they put in the tank and divide it by distance driven?

mantas 9y ago
I know it's anecdata, but I found the dashboard estimate on my VW (heh) strangely correct. It's off by +/- 5% in most cases. Since it doesn't take upcoming traffic/terrain/wind into account, I find it more than reasonable.
gambiting 9y ago
I trust the fuel consumption in my car, yeah. If it says I've been using 12l/100km on average and I've travelled 500km, you can bet I'm filling up exactly 60l at the pump.
- dx034 9y ago
  That really depends on the car. I don't own a car so often use rental cars. Most cars' consumption is within 10% of the shown values but at least every fifth car I drive has vastly different numbers. I think it is not necessarily due to the car but because of the calculation methods they use. If you drive motorway and city, consumption is accurate. But as soon as you start driving in the mountains or a mix of different terrains, data often vastly differs.
  - nateguchi 9y ago
    If the car has a Mass Airflow Sensor (MAF), then it can more accurately calculate the fuel usage. The majority of older / cheaper cars use a Manifold Absolute Pressure Sensor (MAP) and have to make some guesses at what the actual fuel usage is.

friendzis 9y ago

There is one thing about batteries: Watt-hours battery will provide highly depend on current (electric current) draw. To some extent this also applies to deterioration. Which means that as batteries get more and more used, one should expect to see higher and higher disparity between range in sporty and economic driving. In other words as battery gets older, the higher consumption driving aggressively. Tesla, however, has one redeeming factor. While battery voltage-capacity@current curve will change over time, Tesla can collect real world usage data and with software updates push updated curves for older batteries to adjust range estimation models for battery wear.

iambateman 9y ago

Correct me if I'm wrong, but Lithium Ion batteries have exponential degradation, right? The data here assumes constant degradation, which is going to throw this off.

lafar6502 9y ago

So you can conclude your car willl be worth nothing after 200k miles