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Thread: Tesla cars allowing batteries to become fully discharged?

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    Default Tesla cars allowing batteries to become fully discharged?

    Not sure whether to post this in battery forum or here, since the car uses 18650s...

    http://jalopnik.com/5887265/tesla-mo...design-problem

    After reading this article, I'm curious, what were the engineers prioritizing in designing such circuit that would allow batteries to be discharged with no safety cutoff, I mean it's a car, there's plenty of room, I've never used a phone or laptop computers that would allow itself to discharge lithium batteries to the point of damage.... anyone care to speculate?

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    Flashaholic SHADE02's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    woOW, I just read the entire article, man... 40k USD for a new spare batterie,,, thats sucks


    and terrible CS from tesla too...
    and yes , why in the name of hell, they, just simply no put some baterie volts cut-off or something??????!!

  3. #3

    Default Re: Tesla cars allowing batteries to become fully discharged?

    Probably were more worried about maximizing range, and the minimizing the rage a customer would feel towards them if the battery had enough juice to get them to that next outlet, but just refused to drive a little further, etc.

    It DOES seem short sighted to not include some sort of safety net though, perhaps a setting to cut the parasitic drain at least to avoid continued discharges?

  4. #4

    Default Re: Tesla cars allowing batteries to become fully discharged?

    would the protection circuit still drain the battery even after it has dropped enough to trip the cutoff? I'm talking for normal 'protected' cells that we normally use here....

    btw the roadster uses 6831 18650s, if someone were to buy a replacement for all that with say... AW's cells, that would be.... ouch

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    Flashaholic RBR's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by bobbagum View Post
    Not sure whether to post this in battery forum or here, since the car uses 18650s...

    http://jalopnik.com/5887265/tesla-mo...design-problem

    After reading this article, I'm curious, what were the engineers prioritizing in designing such circuit that would allow batteries to be discharged with no safety cutoff, I mean it's a car, there's plenty of room, I've never used a phone or laptop computers that would allow itself to discharge lithium batteries to the point of damage.... anyone care to speculate?
    Hahaha, now that´s a pretty fine example for planned obsolescence.



    Cheers

    RBR

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    Flashaholic ssvqwnp's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    It seems to me they should just give the cars primaries and make the whole thing disposable... The article makes it appear that's what'll happen with the Model S with it's lower price tag and proposed more expensive battery(s).


    [Also, for those that didn't catch it, the first sentence was sarcastic. You know who you are.]

  7. #7

    Default Re: Tesla cars allowing batteries to become fully discharged?

    Tesla was afraid they would get sued by Surefire if they installed a lockout tailcap.
    Last edited by fnsooner; 02-22-2012 at 03:24 PM.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    its the problem with ppl doing something but have not full understanding of everything.
    They probably have a hell of a designer,
    technicials/electricians for normal cars, used to lead batteries, ...

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    Flashaholic* uk_caver's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Would this still happen even if the battery was entirely disconnected from the car?

    It's not clear what a car needs to use meaningful power for when it's unoccupied.

    Are there no consumer-protection laws which would support someone with a bricked car taking action against a manufacturer who seemed to have made some pretty poor design decisions, and who had limited the severity of warnings for the sake of not putting customers off the vehicles.

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    Flashaholic* Sub_Umbra's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    The main issue of this thread is moot as modern electric cars aren't going anywhere (with the possible exception of up to the 7-11 for some Ben and Jerry's for Ed Bagley Jr)

    -- We don't have the GRIDs it would take to charge all of those electric cars. Especially the 'pie in the sky' hype about the ones that pick up a full charge in two hours. OK, so scores of millions all drive their little cars home and plug them in at 6p. Our grids can not cope with a hot day AND NO ELECTRIC CARS all plugging in at the same time.

    -- We don't even have a plan to change our grids to be able to handle it at some vague, nebulous time in the future. (That is really a bad sign in Western culture where we're pretty much willing to lie about nearly anything in the future if it will make us a few bucks in the now.)

    -- The batteries are expensive, fragile, short-lived and like the steam car in
    "The Carpetbaggers" they are not anything that most want to have anywhere near them in a car accident.

    -- All 'Rare Earth' minerals come from China. This will not change in the next ten years. Rare Earth minerals are very important to schemes like this. Without Rare Earth minerals your iPod would weigh three pounds. Rare Earth minerals are not being exported by China the way they have been in the past. Without Rare Earth minerals all of this talk of efficient electric cars is nothing but hucksters pumping venture capital and hoping for inflated IPOs. My point here is that if Westerners decide that they MUST drive electric cars they will, in fact, be made in China into the significant future.

    Frankly, I don't even think that Americans are dumb enough to go this route, especially after it is pointed out to them repeatedly that for all of their 'greener than thou' smugness they have somehow figured out how to feel good about electric cars that actually run on coal. Yup, that's right, in the States most electricity comes from coal. And yes, it will have to be pointed out repeatedly.

    Hey, what could possibly go wrong? I ax ya?

    If I like coal I'm a Luddite, but if I support today's electric cars that run on coal I'm warm, fuzzy, green and adorable.
    Last edited by Sub_Umbra; 02-23-2012 at 08:34 PM. Reason: spellin'

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    Flashaholic* hopkins's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    The Tesla battery module weighs 900lbs. Its liquid cooled. It has 6,800 18650's inside of it. Each of the cells has it own temperature
    sensor and 2 fuses that can be individually triggered to open if a runaway thermal event occurs. There are 12 microprocessors inside the battery
    module that are always on. Cannot be turned off.

    (who knows how many computers are in the rest of the car?) (Lots)

    These 12 microprocessors are always monitoring for unsafe cell conditions and are a constant parasitic drain on the 375volt 53Kw battery.
    There is no way to access them as they are embedded in the 900lb battery module.

    Without a recharging hookup this battery monitoring system will 'Brick' the car all by itself. Drain all the 18650's.
    Current draw seems to be 0.42amps for this safety system.

    Probably some nice vampire dc-dc converters to make 5volts
    for the 12 microprocessors guaranteed to kill the $40,000 battery module.

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    Flashaholic* uk_caver's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    So presumably the protection circuits are there partly in case of physical damage or thermal runaway of an individual cell when the car is not running, to disconnect internal shorts and try to prevent a chain reaction of failure?

    Otherwise it would be possible to turn them off or hibernate them when the car didn't actually need the main battery, and power what few devices actually needed power from a small/cheap battery.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Sub_Umbra View Post
    -- All 'Rare Earth' minerals come from China. This will not change in the next ten years. Rare Earth minerals are very important to schemes like this. Without Rare Earth minerals your iPod would weigh three pounds. Rare Earth minerals are not being exported by China the way they have been in the past. My point here is that if Westerners decide that they MUST drive electric cars they will, in fact be made in China.
    I thought that with rare earths, part of the pont of the supply restriction/internalisation was to encourage other countries to start producing because China expected to be a net importer in the medium/long term.

    The more confident people are that prices won''t suddenly drop and pull the rug from under a new venture, the sooner that alternative sources seem likely to get going.

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    Flashaholic* Sub_Umbra's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by uk_caver View Post
    I thought that with rare earths, part of the pont of the supply restriction/internalisation was to encourage other countries to start producing because China expected to be a net importer in the medium/long term.

    The more confident people are that prices won''t suddenly drop and pull the rug from under a new venture, the sooner that alternative sources seem likely to get going.
    It is my understanding that China reached the monopoly they have today by DUMPING Rare Earth minerals. (Dumping in this context would mean the export of said minerals internationally at below their cost of production in an attempt to shut all other mining operations down. It worked -- it will take a minimum of ten years to begin significant returns on mining operations of rare earth minerals begun today.)

    "...All your electric cars are belong to us..."
    Last edited by Sub_Umbra; 02-23-2012 at 07:38 PM.

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    Flashaholic* uk_caver's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Sub_Umbra View Post
    It is my understanding that China reached the monopoly they have today by DUMPING Rare Earth minerals. (Dumping in this context would mean the export of said minerals internationally at below their cost of production in an attempt to shut all other mining operations down. It worked -- it will take a minimum of ten years to begin significant returns on mining operations of rare earth minerals begun today.)
    Ten years to start meaningful production even in the face of demand and limited supply?

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by uk_caver View Post
    Ten years to start meaningful production even in the face of demand and limited supply?
    Yup. It turns out that Rare Earth Minerals is a very poor term for minerals that are scattered very thinly throughout the entire world. Searching will turn up a big effort in (I think) Kansas. They are dumping boucoup bucks into this and according to the news reports it will be at least ten years before any significant production is reached.

    By all means, look it up and correct me if I've got it wrong.
    Last edited by Sub_Umbra; 02-24-2012 at 04:24 PM. Reason: typo

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    Flashaholic* Wrend's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Sub_Umbra View Post
    ...
    How did this thread get here?

    I think you need to crunch some actual numbers more and make generalized assumptions less.

    Did you know that you could charge a battery powered electric car with a relatively cheap gas powered generator and still get better gas mileage and pollute less?

    The beauty of "going electric" is that it can get its energy from anywhere, and that energy can be used a lot more efficiently.

    The only real hindrance is the prohibitive cost of larger battery capacity.
    Last edited by Wrend; 02-23-2012 at 07:48 PM.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Wrend View Post
    How did this thread get here?

    I think you need to crunch some actual numbers more and make generalized assumptions less.

    Did you know that you could charge a battery powered electric car with a relatively cheap gas powered generator and still get better gas mileage and pollute less?

    The beauty of going electric is that it can get its energy from anywhere, and can be used a lot more efficiently.

    The only real hindrance is the prohibitive cost of larger battery capacity.
    I am not impressed. While you have responded you have not addressed even one single issue I brought up.

    You are making my points for me by your lack of any arguments. Perhaps you who have attempted to bring me to task for making, as you said, "...genralized assumptions..." could take a minute and focus your thoughts. It might be handy for you to comment about things I have posted, instead of commenting on things I haven't ever written.

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    Flashaholic* Wrend's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Sub_Umbra View Post
    ...
    Please don't mistake my post for a conversational "debate." I'm just offering my point of view, not trying to change your beliefs.

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    Flashaholic* Sub_Umbra's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    No worries there.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Wrend View Post
    Did you know that you could charge a battery powered electric car with a relatively cheap gas powered generator and still get better gas mileage and pollute less?
    Outdoor Power Equipment makes a LOT of pollution. We're talking an hour of mowing is something like driving your car 300 miles. And not to mention you'd upset your neighbors running an open frame 5.5KW+ generator every night to recharge your electric car.

    We've got a cheap 5.5kw Harbor Freight unit for power outages. It's a great generator. Will blow through 5 gallons of gas in 8 hours running at 1/2 - 3/4 capacity. We got to test that out during the Halloween snowstorm in the Northeast. So I drive my car 100 miles on 5 gallons of gas. That's, what 20 MPG? I get better than that in mixed city/highway driving in my 360hp car. On straight highway I can get up near 25MPG. And that's an AWD car that weighs about 4000 lbs.

    Oh, and Natural gas generators are about the same as the fuel contains less energy than gasoline.

    A Diesel generator would be the way to go but you have to feed it somehow and it still doesn't get around the fuel and sound needs/issues.

    Electric cars would be great if the infrastructure was there but it's not.

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    Flashaholic* Wrend's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by itguy07 View Post
    ...
    The fuel gas generator would need to be optimized for the task, but what I said is definitely doable. Maybe not with your setup as is, of course.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Putting aside protection circuitry, using 6831(?!) 18650s instead of maybe about 120 of these is just a brain-dead decision. Same amount of energy, less than 1/50 the number of cells to assemble into a pack, 2000 cycles instead of only 300, safer chemistry, costs about the same. OK, the pack would be a few hundred pounds heavier, but with regen braking weight doesn't significantly impact range. Their engineer must have been asleep at the wheel.

    And the grid is plenty ready for EVs now. We're not going from zero to 100 million EVs overnight. We could beef up the grid where and when needed as we go along. I suspect also that solar power will become mainstream in the same time frame as EVs, and lots of people will be charging their EVs off solar power, making the whole grid issue moot. An interesting factoid is that petroleum refining is the single biggest user of electricity in the US. As you go to EVs, more and more of that power will be freed up for charging.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Wrend View Post
    The fuel gas generator would need to be optimized for the task, but what I said is definitely doable. Maybe not with your setup as is, of course.
    Not really. Piston engines (even Atkinson cycle models like which are found in most hybrids and the Volt) are not that efficient. About the best we've got now is turbine engines (Jet engines) and even those are way less efficient than, say a coal or natural gas plant. And I won't even discuss the maintenance that turbines need.

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    Flashaholic* Sub_Umbra's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Lets not forget the energy embedded in the battery during the course of its manufacture. How much oil, gas and coal goes into manufacturing each battery -- that needs to be figured into the mix. From the point of view of operating costs AND reducing foreign energy dependence the cost of the batteries embedded energy must be factored into the mileage figures. On vehicles requiring huge expenditures for new high tech batteries every few years these numbers would blow the conventional mileage figures out the window.

    I think we would have seen these numbers by now if they were good.
    Last edited by Sub_Umbra; 02-26-2012 at 03:13 PM.

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    Flashaholic* Wrend's Avatar
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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Sub_Umbra View Post
    ...
    I'm just making the point that it's possible to effectively charge an electric car with gasoline, which I find kind of humorous.

    I'm not arguing the viability of electric cars and their role in world affairs.

    However, as I've said, I think their only real hindrance when it comes to viability is the currently prohibitive cost of significantly higher battery capacities.

    I also think the drilling, refining, storing, and transportation of oil and gasoline as a whole is very energy needy; so if you're comparing the whole energy use involved, "electric" still comes out ahead from what I've seen. Of course, less so if you're using gasoline to charge you're car.
    Last edited by Wrend; 02-26-2012 at 07:19 PM.

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    Default Re: Tesla cars allowing batteries to become fully discharged?

    Quote Originally Posted by Wrend View Post
    I'm not arguing the viability of electric cars and their role in world affairs.

    However, as I've said, I think their only real hindrance when it comes to viability is the currently prohibitive cost of significantly higher battery capacities.

    I also think the drilling, refining, storing, and transportation of oil and gasoline as a whole is very energy needy; so if you're comparing the whole energy use involved, "electric" still comes out ahead from what I've seen. Of course, less so if you're using gasoline to charge you're car.
    I agree on both counts. Viable electric cars will use a smaller number of high capacity prismatic cells (these are available in capacities as high as 200 Ah). And mass production would bring the cost of electrics under the cost of ICE vehicles. When you think about it, an internal combustion engine with many very high tolerance parts inherently costs more to manufacture than an electric with only a few much lower tolerance moving parts (the bearings in the motors are probably the only high-precision part if you go with hub motors), all other things being equal. Low volumes are why EVs cost more than their gas powered counterparts.

    As for energy to produce fuel, some sources suggest we're rapidly approaching the point where it will take more energy to mine and process the more difficult to extract oil reserves than we will recover burning them. Same with natural gas. Some types of fracking are already energy negative. The real beauty of EVs is that you're not tied solely to fossil fuels to generate the power. They're the ultimate "flex-fuel" vehicle.

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