Forgot your password?
typodupeerror
Power Transportation

Why Tesla Cars Aren't Bricked By Failing Batteries 362

Posted by samzenpus
from the not-do-fast-now dept.
itwbennett writes "Don't believe recent claims made by a blogger that non-functioning batteries in the Tesla Roadster cause the electric cars to be bricked, says IDC analyst Sam Jaffe. 'Here's the primary fact that the blogger in question doesn't understand: the Tesla battery pack is not a battery,' says Jaffe. 'It's a collection of more than 8,000 individual batteries. Each of those cells is independently managed. So there's only two ways for the entire battery pack to fail. The first is if all 8,000 cells individually fail (highly unlikely except in the case of something catastrophic like a fire). The second failure mechanism is if the battery management system tells the pack to shut down because it has detected a dangerous situation, such as an extremely low depth of discharge. If that's the case, all that needs to be done is to tow the vehicle to a charger, recharge the batteries and then reboot the battery management system. This is the most likely explanation for the five 'bricks' that the blogger claims to have heard about.'"
This discussion has been archived. No new comments can be posted.

Why Tesla Cars Aren't Bricked By Failing Batteries

Comments Filter:
  • battery vs cell (Score:5, Insightful)

    by Anonymous Coward on Thursday February 23, 2012 @06:36AM (#39134907)

    There seems to be a fundamental misunderstanding of the terms 'battery' and 'cell'. A battery is the collection of cells. So a Tesla could be bricked by a failed battery but it is tolerant to a failure of individual cells. This is not surprising.

    • Re:battery vs cell (Score:5, Informative)

      by L4t3r4lu5 (1216702) on Thursday February 23, 2012 @07:40AM (#39135157)
      I would have to assume that a Tesla wouldn't be "bricked" by a failed battery either, as the batteries are presumably replaceable by the manufacturer.

      Remember: Bricked = Failed and unrepairable.
      • Re:battery vs cell (Score:5, Interesting)

        by radtea (464814) on Thursday February 23, 2012 @12:33PM (#39137391)

        Remember: Bricked = Failed and unrepairable.

        This is a curious belief. I presume you've not been around embedded technology enough to have ever heard the term "unbrick", which is what people who actually understand the term "brick" used to describe the process of recovering from a bricked state.

        According to your incorrect belief such a term could not possibly exist. And yet it does. So either the world is full of embedded engineers who don't know what they are talking about, or you are simply announcing to the world your own ignorance. Which is kind of useful: everyone here claiming that the Tesla is not "really" bricked by being left uncharged for a few months--as might easily happen to a vehicle in storage, being shipped somewhere, or simply parked near an airport during an extended vacation--is identifying themselves as having nothing useful or interesting to contribute to the conversation.

        Likewise, people claiming that "this can't happen because power management" are declaring their ignorance of electrochemistry, which goes on regardless of external circuitry. Electrochemical cells that are not being actively charged can and do continue to discharge all by themselves regardless of anything any external circuit does. Some types of cell can and do get themselves into an unchargable state after sufficiently deep and prolonged discharge, regardless whether the discharge is passive or active.

        So this "refutation" of the claims against Tesla is nothing but hand-waving anti-scientific bullshit: it is saying, "What has actually happened cannot possibly have happened according to my understanding, and my understanding cannot be wrong so the facts must be wrong." This is no different from the people who claimed that Galileo couldn't have seen the moons of Jupiter because just as there were seven seas and seven openings in the human skull so there could be only seven wandering stars.

        There is a lot of this kind of anti-scientific reasoning about. I recently saw a claim that the Heartland Institute's campaign against second hand smoke laws was based on the "reasoning" that second hand smoke wouldn't be breathed deeply into the lungs and so couldn't cause lung cancer, regardless of the actual empirical data that shows second hand smoke causes lung cancer. This is not "reasoning" in any Bayesian sense: it is gibberish masquerading as thought.

        The same kind of gibberish seems to be all that defenders of Tesla can come up with here. If anyone really believes they can't brick their Tesla by fulling discharging the battery they should drive it to the point of full discharge and let it sit for a while. That would give us new facts to account for, and actually contribute to the resolution of this question.

    • Maybe the setup consists of 8000 batteries, each battery containing several cells.
    • Re: (Score:2, Insightful)

      by Tsingi (870990)

      There seems to be a fundamental misunderstanding of the terms 'battery' and 'cell'. A battery is the collection of cells. So a Tesla could be bricked by a failed battery but it is tolerant to a failure of individual cells. This is not surprising.

      Semantics.

      Statements like that one are what this piece is about. AC either hasn't read the article or is a troll. This is exactly what it explains can't happen, and statements like the one the AC made are the kind of propaganda that the misinformation campaign spreads.

      • Re:battery vs cell (Score:5, Informative)

        by DerekLyons (302214) <fairwater@@@gmail...com> on Thursday February 23, 2012 @09:22AM (#39135629) Homepage

        There seems to be a fundamental misunderstanding of the terms 'battery' and 'cell'. A battery is the collection of cells. So a Tesla could be bricked by a failed battery but it is tolerant to a failure of individual cells. This is not surprising.

        Semantics.

        No, not semantics, but rather proper use of terminology. The AC is correct - a battery [reference.com] is a collection of cells. A battery pack is a collection of batteries. (The battery being the smallest individually replaceable part in the pack.)
         
        That's why a "D" cell battery is called a "single cell battery" - because, duh, there's only a single cell in the battery. That's why automotive type batteries [wikipedia.org] (of the type you add water to) have multiple vent caps - because each individual cell must be separately vented and/or topped off with water.
         
        The quoted IDC analyst adds to the confusion (at least to those of us versed in standard terminology) by using the terms battery and cell interchangeably, which is the same mistake often made by the general public - you for example.

        • Re: (Score:3, Interesting)

          by polebridge (517983)

          > not semantics, but rather proper use of terminology
          Wait, isn't that exactly what semantics is, the proper use of terminology?

          "When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean -- neither more nor less."
          "The question is," said Alice, "whether you can make words mean so many different things."
          "The question is," said Humpty Dumpty, "which is to be master - - that's all."

          • No, semantics is the matter of examining the underlying substance; what is actually being communicated. To provide a computer analogy, what the C program is actually doing once all of the pointers and names are dereferenced to real, hard, memory addresses. If someone makes an excuse starting with "but that's merely semantics," you can slam any and every door in his or her face immediately, as you are most certainly assured that they either don't care what they're actually talking about, or they have just gr
    • Re:battery vs cell (Score:5, Insightful)

      by geekmux (1040042) on Thursday February 23, 2012 @08:14AM (#39135319)

      There seems to be a fundamental misunderstanding of the terms 'battery' and 'cell'. A battery is the collection of cells. So a Tesla could be bricked by a failed battery but it is tolerant to a failure of individual cells. This is not surprising.

      There seems to be a fundamental misunderstanding of the terms 'brick' and 'won't start'. I know it's clearly far too late as I stare at a page of comments that look like "this" or 'this', but let's at least try and keep the IT geek terms out of the automotive industry, no matter how many "Intel Inside" bumper stickers you may run across.

      Might I remind all of what has happened to the term "hacker" in mainstream media. I don't need or want to be labeled as a criminal for simply trying to get my damn car to start in the future, which is likely the more accurate terminology no matter what is under the hood. Mechanics probably have no idea why people keep talking about a "brick" either, for the automotive shop doesn't stock "mortar" for repairs.

    • Sssh! That isn't scary enough for news.
    • Re:battery vs cell (Score:4, Insightful)

      by EasyTarget (43516) on Thursday February 23, 2012 @08:30AM (#39135397) Journal

      So a Tesla could be bricked by a failed battery but it is tolerant to a failure of individual cells.

      No.. A Tesla cannot be bricked by a failed battery. It is merely a Tesla with a flat battery.. nothing more.

      Terminology here is quite important, the negative word 'bricked' is being used to try and transfer a operator failure (running out of battery) into a criticism of the product itself.

    • CellBatteryBattery Pack.

      The battery pack is tolerant to a failed cell or battery.

  • whew (Score:5, Funny)

    by Anonymous Coward on Thursday February 23, 2012 @06:36AM (#39134919)

    Good thing slashdot is here to help us debunk everything I'd never have heard about from random dipshit bloggers.

    • by Xest (935314)

      Yes, the real morale of the story is "Don't give a fuck what dipshit bloggers say". Going on to then debunk what they say publicly only feeds their blog views more and hence increases their ad revenue, which in turn makes it more profitable to be a random dipshit blogger talking utter shite.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      Except this has been making the rounds, not just a dipshit blogger

      http://jalopnik.com/5887265/tesla-motors-devastating-design-problem

  • Tow? (Score:4, Informative)

    by oniony (228405) on Thursday February 23, 2012 @06:41AM (#39134935)

    >all that needs to be done is to tow the vehicle to a charger

    Another claim was that the vehicles cannot be towed.

    • Re:Tow? (Score:5, Interesting)

      by Jack Malmostoso (899729) on Thursday February 23, 2012 @07:06AM (#39135031)

      Well technically towing an electric vehicle, missing a clutch, would make it a generator, which could possibly damage the battery. However there is a youtube video showing a Nissan Leaf being towed and the battery being recharged. Don't try this at home!

      Another option with the Tesla could be to lift the back wheels and tow it with the front wheels on the ground, unless there is some regenerative braking system which still acts as a generator. And yes, you want to lock the wheels if you do that.

      • Re:Tow? (Score:5, Funny)

        by Joce640k (829181) on Thursday February 23, 2012 @07:30AM (#39135113) Homepage

        Just make sure you tow it backwards...

      • by ledow (319597)

        I'd be extremely disappointed (but not at all surprised) to find that a car manufacturer *HASN'T* considered how to tow an electric vehicle. I suppose they just expect people to know this and book a tow truck that picks the car off the road (but then - how do you get it onto that truck without a crane?).

        I'd be less surprised if your average vehicle recovery firm wouldn't know about whatever-method and tow it anyway.

        I also would be 100% completely unsurprised if most electric car owners have no knowledge of

        • I don't think pulling a Tesla twenty feet from the roadside onto a flatbed truck is going to do a whole lot of damage. With that said, there are tow trucks that incorporate cranes to lift a vehicle bodily from the road; they're often used for parking enforcement. However, as you pointed out, a towing company would have to have such a truck and the wisdom to use it.

          As for towing over distances with the front wheels lifted, that depends entirely on which axles the regenerative braking system operates.

          • Re: (Score:3, Insightful)

            by d3ac0n (715594)

            This entire article is stupid. Essentially they are making the technical claim that the car isn't REALLY "bricked" because "Only one or two cells are really bad, and they can be fixed."

            Here's the problem with that argument: If a handful of bad cells in a battery pack cause the pack to be unusable, AND the car to be un-tow-able AND require the ENTIRE PACK to be replaced at a very high cost, then for all intents and purposes the car IS "bricked".

            Techno-sementic arguments about the precise definition of "bri

      • I don't think that can be right. Otherwise, you would damage the car by switching off the engine at the top of a long, steep hill.
      • Re:Tow? (Score:5, Informative)

        by Teancum (67324) <robert_horning AT netzero DOT net> on Thursday February 23, 2012 @07:54AM (#39135233) Homepage Journal

        However... the Tesla vehicles already take advantage of "becoming a generator" as that is part of the "regenerative braking system" used in the vehicle. That ability to "generate electricity" not only doesn't damage the battery, but it helps to recharge the system as well and is an intended behavior... at least if you are going downhill with a tailwind.

        I've seen several electric vehicles that have a gasoline-powered "pusher" trailer that provides "emergency power" for long haul trips instead of looking for an outlet for the car. It isn't even that new of an idea for that matter.

        Regardless, because of the simplicity of the drive train and that the engine is not an internal combustion engine, calling a dead Roadster "a brick" is going over the top even if you can't disengage the engine from the transmission. Yes, there is a transmission in a Roadster, and there was even going to be a "clutch", but that feature was removed due to the torque issues and other problems from the supplier that was originally going to provide the transmission (something that nearly killed the Roadster when it went into production).

        The Roadster is a rear wheel drive vehicle, so I don't think the front wheels are connected to anything other than the steering mechanism. In that regard, it is more like a conventional automobile too. In other words, towing the car is just like towing any other vehicle when you don't have the keys to unlock the transmission from the drive train.

        • Re:Tow? (Score:5, Informative)

          by necro81 (917438) on Thursday February 23, 2012 @09:36AM (#39135703) Journal

          the Tesla vehicles already take advantage of "becoming a generator" as that is part of the "regenerative braking system" used in the vehicle

          Regenerative braking requires some pretty sophisticated power electronics, controls, and software. The Tesla's motor [teslamotors.com] is an AC induction motor [wikipedia.org]. (The AC induction motor was invented by Nikola Tesla [wikipedia.org].) An AC induction motor has copper coils for both the rotor and the stator. This is different from a DC motor (brushed or brushless) where (usually) the rotor has permanent magnets on it.

          Backdriving an induction motor will result in no power generation unless the stator is energized. Even then, the associated power electronics have to commutate which phase of the stator is energized in sync with the spinning rotor. In other words, you need at least some external (i.e., battery) power in order to regenerate - this is true of all induction generators [wikipedia.org]. Without the stator being energized, you're just spinning one set of copper coils past another set (this is different from a DC motor, where the rotor has permanent magnets, which will induce current in the copper coils).

          So the Tesla cannot be "jumpstarted" by towing it or rolling down a hill if the battery has discharged so deeply that it has disabled itself.

        • by tgd (2822)

          I've seen several electric vehicles that have a gasoline-powered "pusher" trailer that provides "emergency power" for long haul trips instead of looking for an outlet for the car. It isn't even that new of an idea for that matter.

          Not pushers, just generators in a trailer, plugged into the car. A car would be nearly impossible to drive if you had something behind it, attached at a rotating pivot point, actually pushing the car. The generator is producing the electricity, not the motor in the vehicle. That's why trailers have their own brake systems -- its extremely dangerous to have the load behind a vehicle doing anything more than being pulled by the vehicle.

      • by mwvdlee (775178)

        Don't all electric vehicles recharge from the wheels already? It would be such a waste of energy when breaking, since you already have most of the hardware to utilize this energy.

      • by AmiMoJo (196126)

        You assume that the batteries are connected directly to the wheels, but of course there is a battery management system that will prevent them from changing dangerously while being towed.

      • Re:Tow? (Score:5, Informative)

        by necro81 (917438) on Thursday February 23, 2012 @09:41AM (#39135725) Journal

        Well technically towing an electric vehicle, missing a clutch, would make it a generator, which could possibly damage the battery

        that depends entirely on the architecture of the motor, motor drive, and battery management circuits. The Tesla roadster, for instance, uses an AC induction motor, which has no permanent magnets in it. Unless the stator is energized and properly commutated, backdriving the wheels will not generate any power. Even in the case of a DC motor, backdriving the wheels will generate power, but if the motor drive is disabled, that power won't backfeed onto the power bus. Even then, if the battery has discharged so deeply that it has disconnected itself internally, it won't accept power unless it first communicates with a compatible charger.

      • by Xacid (560407)

        Another option with the Tesla could be to lift the back wheels and tow it with the front wheels on the ground

        This is pretty much standard procedure for towing AWD vehicles as well so it's not like the capability/knowledge doesnt widely exist. This whole thing is FUD.

      • by mea_culpa (145339)

        Every tow truck I've called over the last 15 years were a flat bed type. One of my cars ejected a wheel while driving. The tow truck had no problem dragging the car 15ft onto the flatbed and returning it to the dealer.
        Unless Teslas have some magical tires the permanently grip the road when their batteries die I don't see any reason why any tow truck company could not easily tow it.
        Dragging a car 15 ft up a ramp isn't going to regenerate anything significant.

    • Re:Tow? (Score:4, Informative)

      by phoebus1553 (522577) on Thursday February 23, 2012 @08:20AM (#39135345) Homepage

      Another claim was that the vehicles cannot be towed.

      Maybe by a rope and your backwoods service jockey.

      Winch it onto a flatbed, even locked wheels skid. Can't get to an end of it because it's parallel parked? There are these funny little things that scoop each wheel and then you basically push it sideways to wherever you CAN lift it. If you are towing something with AWD without a flatbed handy? Lift one end like anything else and use the wheel-scoop style things to jack the other end off the ground and tow it on them.

      There are ways, and a good tow service knows them.

    • Recovery vehicles that take the car completely off the road are not rare. And cost rather less than $40,000 to hire.

  • by larwe (858929) on Thursday February 23, 2012 @06:45AM (#39134947) Homepage
    It's a shortcoming of LiIon technology that if the cell becomes over-discharged, the cell may fail short circuit, and a subsequent recharge may cause an "exciting" failure (think flames). That's why all LiIon packs have a protection circuit that permanently disables the pack if it's discharged to the danger zone. Given the massive size of an automotive battery pack, it's easy to believe they have some very conservative safety devices in them. And it's also easy to believe that the cost of individually testing/replacing cells and "rebooting" the protection circuitry in a pack that has tripped its safety limits is prohibitive.
    • OK. so my question is then: what does "bricked" mean, technically, in the Tesla battery case? If a protection circuit has kicked in and isolated the battery, then that should save the battery itself from permanent damage. The story is that Tesla is charging $40,000 for replacement of the complete battery pack, which suggests that a protection circuit has NOT saved the battery from permanent damage. Either that or the battery can be fixed and resold, and they're ripping off the customer. Those are the only p

  • Weak! (Score:2, Interesting)

    by Anonymous Coward

    "The battery management system of the Tesla Roadster keeps the battery from being discharged to a damagingly low state of charge under normal driving conditions."

    One of the original points was that if the car was left alone for a relatively short period of time then it would discharge fully due to physics, nothing the power management system can do about it.

    This is a pathetically weak rebuttal to be honest. Take each one of his points and give us a counter-point to each one. So far it seems to be "He doesn'

  • by Jack Malmostoso (899729) on Thursday February 23, 2012 @07:03AM (#39135019)

    When I read the blog article I thought exactly the same thing. Cells left to self-discharge will not go below their thermodynamic equilibrium, which is more or less the potential at which they are built (remember, Li-ion batteries when assembled are discharged by nature). There is no danger of damaging the cells when self-discharge occurs.
    Another issue is when the cells are actively overdischarged, however a Li-ion battery is more likely to explode due to overcharge (plating of Li metal at the negative electrode) than overcharge (insertion of too much lithium in the cathode and electrolyte depletion).

    Most likely the BMS is refusing to come back to life unless hooked up to a secret Tesla computer, but I guess the packs can be refurbished.

    Also, kudos to the idiot recharging the car with a 30m cable extension (that's what 100 feet is, right?).

    • by Inda (580031)
      Tell us why the man is an idiot for using a 30m cable.

      It's the same cable that my house is wired up with and I have certificates showing its safety (needed some re-wiring in my kitchen, UK law states whole house needs checking).
      • by necro81 (917438)
        Ordinarily it probably would not matter: 30 m of heavy gauge copper is usually a non-issue for supplying electricity. However, when you are trying to transfer many kilowatts of power from the charger to the battery pack, the extra resistance and inductance of a 30-m cable is significant. The charger has no way to know that the extra resistance is due to a cable - it may interpret that as extra resistance in the battery itself - a sign that it is reaching end of life. Extension cords are generally unsafe
  • ... do we need to reboot cars now?
  • by bgarcia (33222) on Thursday February 23, 2012 @07:14AM (#39135079) Homepage Journal
    From Tesla's own description of their battery pack [teslamotors.com]:

    Sixty-nine cells are wired in parallel to create bricks.

    AHA!!!! SEE? They admit it!!!

    • by Teancum (67324)

      Admit what? That they have a real battery pack in their vehicles? I had no idea that anybody doubted that the Roadster was an electric vehicle.

      • by bgarcia (33222)

        Admit what? That they have a real battery pack in their vehicles?

        Admit that you wouldn't get the joke even if it was a BRICK HITTING YOU IN THE FACE.

  • Which Battery? (Score:5, Informative)

    by labnet (457441) on Thursday February 23, 2012 @07:41AM (#39135165)

    When you hear Lithium Ion Battery, you need to understand there are many different types of cell.
    A battery consists of an Anode, Cathode and Electrolyte.
    In LiIon based batteries, the electrolyte is a Lithium Salt, and the Anode is generally Carbon.
    In LiPolymer batteries the electrolyte is held in a polymer of Lithium Cobalt or Lithium Maganese (this is the most common format of battery in consumer electronics)
    In a recent project a for a hand held RF device, we chose LiFePO4. Mainly because it is so robust. Although it does not have the same capacity as LiPoly, you can grossly overcharge it and even drive a nail through it and it wont catch on fire. It also has much longer life over LiPoly.

    LiPoly are very sensitive to overcharge, overdischarge, and mechanical damage, thus have a circuit to disconnect the battery when over discharged, thus the 'bricking' effect.

    Tesla orginally used 18650 LiIon batteries with I believe had a LiCoO2 cathode, although I now think they are changing to pupose built cells. They would have a more sophisticated battery management that would prevent 'bricking'...... well at least one would hope...

    • A battery consists of an Anode, Cathode and Electrolyte.

      No, a cell consists of those things - a battery [wikipedia.org] is a collection of one or more cells. The public often confuses the two because the batteries most often encountered in day-to-day life are in fact (technically speaking) single cell batteries.

  • The extent of work required upon the failure of a single cell depends on configuration of the cells and the Battery Management System. (BMS).

    If Tesla is using 8000 cells, it is probably putting something like 6-12 cells in parallel packs, and then wiring up each of these packs of cells in series. The parallel cell packs provide the current capacity while the packs in series provide the high voltage required to operate the motors.

    If an individual cell in a pack goes bad by having a degraded capacity, th

  • by PolygamousRanchKid (1290638) on Thursday February 23, 2012 @07:46AM (#39135199)

    Folks who don't understand what the term originally meant, now use it to describe any tech problem as bricked. As in:

    "My browser says 'page not found' . . . my system must be bricked! I read that 'bricked' means 'not working' in the IT business . . . right?"

    • Yes, the term is overused. However, the usage in the original blog post was borderline to acceptable (even if it was wrong). The original blog post said that the Tesla Roadster became unusable if the battery pack became discharged beyond a certain point unless a fairly expensive part (the battery pack) was replaced. Since the claim was that the car could not even be rolled somewhere in this condition the use ofthe term "bricked" was appropriate. Of course, this story is about arguing that the original blog
  • by BobK65 (2541842) on Thursday February 23, 2012 @09:04AM (#39135555)
    It seems Jaffe only speculated the five bricked cars only needed servicing. Jalopnik did the research and also got an admission from Tesla. http://jalopnik.com/5887265/tesla-motors-devastating-design-problem [jalopnik.com]
  • Uh... you can easily burn out a lithium ion battery like the ones tesla uses by going below 1% charge. If their system isn't intelligent enough to completely stop battery use at 3%, and report that as 0, it's entirely possible to kill the whole power plant.

  • by MarkvW (1037596) on Thursday February 23, 2012 @10:44AM (#39136273)

    Slashdot is losing it (whatever it is). This article is pure Tesla Co. press release.

  • Oh boy. (Score:5, Informative)

    by loshwomp (468955) on Thursday February 23, 2012 @12:58PM (#39137705)

    Just what we need--more "analysts" fighting bad bloggers' bad information with more bad information.

    Let's start with the "more than 8000 individual batteries". These are 18650 cells (a standard form factor, a bit larger than an AA cell), and a Roaster has only 6831 of them. They are not "individually managed". Rather, they are grouped into a 69-parallel module, with 99 modules in series. (69x99==6831)

    It is asinine and a distraction that Tesla (and everyone else) constantly obsesses about the 6831 cells. For all practical purposes it is a 99-cell Li battery, but rather than using monolithic cell modules, Tesla (like ACP before them) builds modules from smaller component cells, because they yield better cost ($/Wh) and specific energy (Wh/kg), with more-favorable cooling and safety characteristics.

    Other than a built-in per-cell PTC device (which Tesla is likely no longer using), any "management" is done at the module level, and the battery is treated as a 99-cell series pack. The PTC is a passive cell protection device, designed to save a cell from a failed-short condition, but they also cause as many problems as they prevent.

    Secondly, the "solution" is not nearly as simple as "shutting the pack down" when it reaches "an extremely low depth of discharge".

    The Li cells themselves do not discharge themselves quickly when idle--perhaps 5 or 10 percent per year. However, small parasitic (e.g. maintenance) loads will slowly deplete the cells' energy. Herein lies the "grain of truth" that is probably at the center of this greatly dramatized "journalism".

    Li traction batteries typically have on the order of 100 cells (or more for 600V systems), and each cell must be monitored to keep its voltage and temperature within a safe range. Typically the monitors are powered from the cell modules directly, and the competing design constraints are many: Small packaging, low cost, low power, electrical isolation, and so on. It is possible, but not trivial (nor cheap) to make a cell monitor draw zero current when its host module is at low voltage.

    The original rant (er, blog) claimed that the parasitics would deplete a battery in 11 weeks, which is bordering on implausible, and if true, it would represent a staggeringly high rate of self discharge. Per Chelsea Sexton (who knows what she's talking about), there has not been "a single 'brick' story that didn't involve some extraordinary circumstances".

    Lastly is the notion that the traction pack is necessarily destroyed by a deep discharge event. While it is true that deep discharge (and particularly cell reversal) will cause some permanent damage, the damage is in the form of higher impedance, and this is far from rendering the module useless. The battery can be brought back via trickle charging and a per-module impedance test will reveal if any are too far gone.

  • by sjames (1099) on Thursday February 23, 2012 @01:22PM (#39138039) Homepage

    A proper battery management system will shut down absolutely everything (including itself) when the battery is approaching full discharge. In that state, there's no reason the battery pack shouldn't be able to go for a year or two without reaching the point of failure.

    Likewise, a proper system would allow the management system to power back on (reboot) when the car is plugged in, and then begin recharging the battery.

    The cheapo protected 14500 (AA sized) LiIons I use here have that feature. The disconnected discharge rate is a few micro-amps. If I run it "flat", I can stick it in a charger days or weeks later and charge it back up. Apparently, the Tesla never actually shuts down standby systems and as a result the battery can be irreparably damaged by sitting for 11 weeks (if starting from a full charge) or much less (if the car was driven before sitting).

    Other electric and hybrid vehicles do the right thing and go into total shutdown when the battery gets too low. Then you wake it up by plugging it in.

    This isn't a general problem with electric and hybrid vehicles, this is a glaring design flaw in the Tesla.

What this country needs is a good five cent microcomputer.

Working...