Hacker Discovers Usable Battery Capacity For Multiple Versions Of Model S & X

4 months ago by Steven Loveday 48

Tesla Model S Chassis Cutaway

Tesla Model S Chassis Cutaway

Technology hacker, Jason Hughes, has been able to gain access to Tesla’s battery management system. He discovered some very interesting information about the “actual” battery capacity of various Tesla models, as well as the “usable” capacity.

Tesla Battery Pack Teardown

Tesla Battery Pack Teardown

Hughes has hacked into the batteries in the past, but only by doing an actual teardown of the battery itself.

This gave Hughes a very good idea, and made him aware that the batteries aren’t necessarily exactly as advertised (due to rounding). He also came to the conclusion that usable capacities differ from model to model, and don’t follow a strict percentage.

However, this new data that Hughes has been able to gather, should be much more accurate, since it comes directly from Tesla’s battery management system software.

Here is what Hughes found, per Electrek:

Original 60 – ~61 kWh total capacity, ~58.5 kWh usable.
85/P85/85D/P85D – ~81.5 kWh total capacity, ~77.5 kWh usable
90D/P90D – ~85.8 kWh total capacity, 81.8 kWh usable
Original 70 – ~71.2 kWh total capacity, 68.8 kWh usable
75/75D – 75 kWh total capacity, 72.6 kWh usable
Software limited 60/60D – 62.4 kWh usable
Software limited 70/70D – 65.9 kWh usable

So basically, when you buy a software limited S 60, you are getting a bit extra for your money. You can then drop $10,000 and bump it up to a 75. But actually, the 75 has only about 10 kWh more capacity than the software limited 60 (not 15, as the model names suggests). Tesla is smart, however, and has never said that you are getting 15 more kilowatt hours. Instead, the company says that the upgrade adds 25% range.

In the end, you can look at the numbers and figure out the best deal. The limited S 60s are surely a good buy, but upgrading them is not. On top of this, the limited Model S 60 can be charged to 100% everyday without harm, because you are not actually “filling” the battery. Also, it charges faster because it is really a 75 kWh battery. It is also important to look at the price difference between the 60 and the 75 (~$6,500), versus the $10,000 “after the fact” upgrade price.

This doesn’t all come up so readily with other EVs, because you have to search for the battery capacity, as it is not included in the model’s name. Of course, EV insiders likely know all the battery capacities (stats here), but not necessarily the general public, or a new buyer.

Source: Electrek

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54 responses to "Hacker Discovers Usable Battery Capacity For Multiple Versions Of Model S & X"

  1. DJ says:

    And here comes the class action.

    If this is true and I bought an 85 or a 90 I would be pissed. Remember all the people that got pissed their hard drives weren’t actually the listed amount of GB!

    1. pjwood1 says:

      I noticed this “‘gate” thread come up, on TMC.

      WK057 can defend himself, but what he really said in his latest salvo was to acknowledge that the MS85 has 85kwh, the MS75 has 75kwh and the 60 also now has 75kwh. He, himself, is now saying none of them fall short on delivered batteries, where I believe this used to be his position (that the 85 had 81kwh of total batteries on board).

      All cars have a discharge window, and this is now what amounts to his (odd) complaint. He’s accurately pointed out that “60” customers are getting a bonus, that is only 10kwh behind MS75 customers (~62kwh usable), but has chosen to frame is as Tesla pulling wool over everyone’s eyes.

      I’m not a fanboy of Tesla, to be clear. They were dead wrong in the Netherlands, and paid for what amounted to a 691HP lie. Here, they also miss-lead (heavily), but always escaped legal obligation with Elon’s careful “motor power” wording / weirdness. Anyway, this issue WK057 is pointing to would be like taking on GM over the original Chevy Volt claiming 16kwh on board, with users only getting 10.5kwh. Every PHEV/BEV has a “usable” kwh which is lower than what is onboard. No biggie.

      1. pjwood1 says:

        ..I’d edit the first para to end with “now, he says the same 81kwh, but as “usable” kwh.”

        I was actually encouraged, not discouraged, by this whole thing. Tesla is discounting the same batch of 75kwh cars it over-produced in Q3. Not like those extra 10kwh are expensive, if you’re willing to buy with 1-2k on the odometer.

    2. Four Electrics says:

      Class actions are typically brought only against companies that have money.

  2. tosho says:

    To say that a li-ion battery has a “total capacity” is not quite correct. You can overcharge any battery to a much higher capacity than the one recommended by the manufacturer. The “total capacity” is just the number that will provide a good balance between capacity and battery life. And the numbers discovered by this “hacker” will probably be quite different for each individual car.

    1. unlucky says:

      You cannot overcharge a Li-Ion battery to a much higher capacity than the one recommended by the manufacturer. You can overcharge it a little bit, but not much.

      1. tosho says:

        Well, it depends on how you define a “little bit”. I guess most li-ion cells could accept 105% without much hassle. In the case of a Tesla, this would equal to 4-5kWh.
        Anyway, my point is that there is no such thing as a “total capacity” for batteries. In fact, you can’t even measure the capacity of a battery directly. You only charge it to a predefined voltage and assume that it is full. The battery management system “knows” the capacity of its battery only by measuring how much electricity it provides while discharging from full to empty. And this number is different for every individual battery, every discharge and depend on the discharge rate or even the ambient temperature. Only people who don’t know how batteries work would say that Tesla is lying or that someone could sue them because of the “capacity” numbers posted by a random guy on the internet.

        1. unlucky says:

          5% is not a “much higher” capacity.

          I don’t know what it would take to bring a lawsuit. But if Tesla said you had “70kWh software-limited capacity” and you really had 66 when new you might be able to get somewhere.

          For the non-software limited units you’d have less case because there never was any representation of the usable capacity just the nominal capacity.

          1. DJ says:

            So if the nominal capacity is under what they sell the car at that is not a problem?

            I guess I just don’t see it that way but then again I’m not one of the cult members.

            1. Nick says:

              > but then again I’m not one of the cult members.

              You are, just a different cult. 🙂

            2. unlucky says:

              These figures don’t include one for nominal capacity other than the marketing one. So it’s unclear if the nominal capacity is lower than promised.

  3. cmina says:

    I wish there were also an EPA certification/specification of the pack for EVs so we don’t have to deal with the marketing crap.

    “And here comes the class action.”
    In your Tesla-hater dreams ..
    Sadly, they probably are covered in some way otherwise this wouldn’t have went on as far as it did.

    1. Nix says:

      They would get as far with a lawsuit, as BMW 335i owners would get for suing that it has a 3.0 liter engine that is the same displacement as the 330i engine, instead of a 3.5 liter engine

  4. Someone out there says:

    Tesla is skimping on the battery? Oh dear, that doesn’t look good! If I had paid for 85 kWh I would certainly expect to get at least 85 kWh!

    1. cmina says:

      “Tesla is skimping on the battery?”

      I doubt they could “skimp” on the battery as the chemistry is what it is and the format is fixed.
      You could take out modules but that’s about it.

      I’ve heard about use of “blank cells” inserted in the lower capacity packs but even with all the pack teardowns shown on the internets I still haven’t seen at least a picture of an 85 or 90 pack containing these blanks. If anyone has more info on this, please share.

      1. Someone out there says:

        Manufacturing tolerance is hardly an unknown concept for Tesla. They know what the cells can hold so if the manufacturing process can’t provide the advertised capacity they either need to add spare cells or change their advertising.

  5. unlucky says:

    If you bought a software-limited 70 instead of a software-limited 60 then you really didn’t get much. Were the prices different or was it just a “free upgrade”?

  6. SteveSeattle says:

    Would love to see the numbers for the 100

    1. bro1999 says:

      The 100 is what a 90 should be. Lol

    2. MikeG says:

      I would too. My hunch is that the 100 is much closer to 100 kWh usable to get the range numbers they are quoting.

      It seems that the software limited battery models provide more value than non-limited models.

  7. Bill Howland says:

    I always wondered why the ’85’ would only go a little further than the ’60’ and it was always explained to me it was battery weight, or wires or magic wands.

    Now I know why.

    1. TomArt says:

      Yep. The problem is in the marketing…the “85” should have been “80”. Poor decision at Tesla.

  8. Ford Prefect says:

    How is this different from getting a 2.0L engine when it is really a 1.9XXL or 1.0L that is really a 985cc? BMW plays with this all the time, a 28 once meant 2.8L, but depending on the model, it can be a 2.0L 4 cyl or a 2.8L 6cyl.

    1. TomArt says:

      It isn’t, really. It just would have been smarter, in retrospect, for Tesla to have had “80” instead of 85, and “85” instead of 90. That would have been accurate.

      OF course, it’s simply an assumption on our part as consumers that the number in the model name actually refers to approximately the nominal pack kWh. In retrospect, I guess it doesn’t have to…but they should have put the model numbers closer to the actual pack values.

  9. Some Guy says:

    Tesla should sue people like this for revealing proprietary information. Usable capacity is a trade secret.

    1. Steve says:

      Exactly how is taking apart a product you purchased and testing its performance metrics illegal? You people are hilarious, let people do what they wany

      1. Some Guy says:

        Yeah. Let hackers do whatever they wany.

        I hope Tesla stops honoring his warranty. He voided it.

        1. cmina says:

          You are hoping for silly things .. he did nothing wrong there, and definitely not on his own vehicle.
          He’s actually quite a nice guy; you should go read his site.

      2. DJ says:

        So you’re pissed that some guy caught Tesla in a lie? I’m confused.

        Wouldn’t this be a good thing for the consumer, regardless of manufacturer. I fully understand the difference between the full battery size and the usable battery size however if you’re selling your car as having a 85kWh battery yet it only has 81.5 kWh total capacity, ~77.5 kWh usable that is a problem. Mind you not because of the 77.5kWh usable but because it’s what 4% under what it is rated. Why not just call their 100kWh car a 150kWh car. Where does it stop. If it’s a tiny bit here/there I don’t think most people would care but this is a big enough gap that I would think a lot of people would and frankly should care.

        1. Pushmi-Pullyu says:

          DJ said:

          “So you’re pissed that some guy caught Tesla in a lie? I’m confused.”

          You’re confused, all right.

          Let’s restate the very same thing in terms that do not assume the conclusion that Tesla “lied” as the premise!

          Tesla chooses to leave a buffer at the “top end” of its battery cells, to improve battery life. This is perfectly normal; the rule of thumb used to be an 80%/20% cycle for li-ion batteries, with 20% left unused on both top and bottom. As I understand it, and according to the numbers above, Tesla is actually using less than this now, so if anything, Tesla is giving its customers more than they paid for.

          Still unconvinced? Look at it another way: Let’s say you sell batteries for home solar energy storage. Let’s say that a customer buys 50 kWh worth of batteries from you. Then that customer calls you up and complains that he can’t use all 50 kWh of the battery pack, because that would wear them out too fast, and he can only safely use ~42.5 kWh, and he demands his money back on the other 7.5 kWh.

          What is your response? You might tell him off and hang up, or you might calmly explain that you are using the industry standard, and that the customer was absolutely not cheated in any way.

          What you are not going to do is send him a refund, nor admit you did anything wrong… because you didn’t.

          1. unlucky says:

            There is no guarantee that this represents a buffer and not simply the pack being shorter on usable capacity than indicated.

            Furthermore if there is a buffer we don’t know it’s at the “top”. It’s about as likely it is at the bottom, given Tesla’s previous concerns of “bricking” due to the battery reaching full discharge.

            Using only 80% of a pack is rare in EVs. The packs are so expensive it’s just not usual to leave so much unusable.

            I’m sure you’re right they don’t all measure out this way. But given no other info there’s no reason to think this pack is unusually low. Heck, maybe these packs are better than average.

          2. mr. M says:

            When it’s written that i shall get a 85kWh battery in the document and i get 81.5 kWh total capacity, ~77.5 kWh usable Tesla lied to me. There is a difference between what you print on the back of the car and the purchase contract. I don’t know about the sales contract of tesla, but on the Homepage i see that they state the ModelS 85 has a 85kWh battery. I BMW sell me a 3.0L Motor and i get a 2.5L they betrayed me.

            But since i get the range that Tesla stated, it should be kinda ok.

    2. Pushmi-Pullyu says:

      Wow, what country do you live in? Here in the USA, thank goodness, we have freedom of speech.

      Something is a trade secret only so long as it can be kept secret. Now, if someone sneaks into a company’s office and rifles through their files to get trade secrets, hacks their computers for the same purpose, that’s illegal and ought to be. But hacking into the BMS (Battery Management System) software of a car you own, or is loaned to you by the owner, to tease out data, isn’t in any way illegal.

      “Good hacking is a gift.” — Elon Musk

      http://h3llowrld.com/elon-musk-said-good-hacking-is-a-gift/

  10. CT says:

    I have a p85d and I honestly don’t care very much. The car performs awesomely. It’s really what matters .

  11. Pushmi-Pullyu says:

    What a tempest in a teapot! Well, this will certainly give the anti-Tesla bashers more ammunition for their FUD.

    As I understand it, here’s the real story: Tesla is not allowing its battery cells to be as charged to the full voltage given by the manufacturer as the cells’ nominal voltage rating, to extend battery life, yet is using Panasonic’s nominal rating in the name of the car; that is, S85 means — nominally — 85 kWh of battery capacity, altho usable capacity is less because the cells are not quite charged to full rated voltage.

    The suggestion that anyone could successfully sue Tesla over the difference between nominal voltage and used voltage is downright silly. A Tesla car has a certain range, can be charged at a certain rate, and capacity is lost at a certain very slow rate as the batteries go through charge/discharge cycles. Those numbers wouldn’t change on bit if they renamed the S85 to be an S8.5 or an S8500. As Shakespeare put it: “A rose by any other name would smell as sweet.”

    I rather suspect every maker of PEVs engineers its cars’ battery packs to use less than the full voltage capacity listed by the battery cell manufacturer. So if you’re gonna get upset at Tesla over using nominal figures instead of what they’ve engineered the car to use, then get mad at the makers of every other PEV on the market, too.

    In describing the battery capacity of its cars, Tesla is using the standard rating used by the battery industry: the nominal voltage figures given by the manufacturer, rather than whatever voltage the batteries are charged to in practice. Castigating Tesla for using the industry standard is entirely inappropriate, period. So far as I know, it’s the standard that all EV makers use.

    And also, I’m far from convinced that every single Tesla car will have the exact same usable capacity as this guy measured… or that every car had that capacity even when it was new. Panasonic keeps improving the battery chemistry year-on-year, and that means the energy density improves. The cells which Tesla uses in its cars in one year will almost certainly measure differently than cells used in another year.

    So unless this guy is analyzing cars which were made using exactly the same battery chemistry, then he’s not really doing an apples-to-apples comparison.

    While interesting, I don’t think the numbers listed above should be considered some sort of exact standard which is matched by all Tesla cars, not even when they were new.

    1. TomArt says:

      Not really – the nominal pack for the 85 and 90 are way off. The 85 should have been “80” and the 90 should have been “85”. The rest are in line.

  12. TX NRG says:

    “anti-Tesla bashers” was probably meant to be “Tesla bashers”

    1. Pushmi-Pullyu says:

      It’s not often I get called on my grammar, but okay, fair cop. 🙂

  13. JR says:

    Being a still happy 85D owner more than 1.5 year i wonder today if the better buy would have been the 70D, but proberly i would have waited for the 100D insted, also Tesla newer stated any thing about the actual max and usable capacity like on other electric cars and now we know why, but it would be interisting to have Tesla’s comment on this, and mabey model of the car should have been 80D insted

    1. Pushmi-Pullyu says:

      Or maybe 85 kWh is correct, since that describes the battery cells which the pack actually contains, even if EV makers, including Tesla, choose not to fully charge battery cells to their rated voltage.

      1. JR says:

        Well it still is strange Tesla dont, count max and usable KW like they do in there powerwall, allthough i am happy that that they protect the batterypack, i expect to keep the car for more than 8 years

      2. TomArt says:

        That’s the problem – the 85 isn’t 85…it’s 81, which means that it should have been marketed as “80”, and the 90 is also off by about the same amount, so it should have been the “85”.

        The rest are reasonably in line, though.

      3. SteveSeattle says:

        Couldn’t he have taken the number of cells x Whr rating of each cell to get true rated capacity?

  14. bogdan says:

    His discovery is BS. He forgot to tell the others that the aging of the battery is also implemented in the battery management.
    When u implicate the aging of the battery in this calculation, it all makes sense.

  15. georgeS says:

    If you ratio the range numbers by these “usable capacities” do the numbers make sense?

  16. Jake Brake says:

    So now Tesla jas their own inflated range numbers and inflated capacity numbers. I wouldnt call it creative marketing as much as lieing.

    1. TomArt says:

      As far as I know, the range numbers are not, nor have they been, inflated. The assumed nominal pack capacity in the model name isn’t a big deal, though the “85” should have been “80” and the “90” should have been “85”. The rest appear to be in line.

  17. Younghwan Jang says:

    Even though it is true, I would leave it as it is. Li-ion battery will work longer when charging less than maximum capacity.

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