Thread: Electric cars are a pipe dream

  1. #1361
    Please use Sugar Cane Alcohol Billy T's Avatar
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    Quote Originally Posted by universaldistress View Post
    So you believe that cars putting CO2 into the atmosphere is preferable over clean power stations, be it carbon capture (for food) or nuclear or fusion? How far forward are you thinking?...
    for many years I have been a strong advocate for the ONLY known-to-be-economical form of fuel cycle "carbon capture" - Namely grow sugar cane for fuel and save petroleum for plastics etc. that keeps the fossil carbon out of the atmosphere.

    I also have been a strong advocate of nuclear power (quite possibly starting even before you were born). I have posted many times about it here including suggesting a simple, cheap, way to get rid of high level waste for in excess of 10 million years. (quick summary: it is "glassified" into disks about 30cm in diameter and 3 cm thick and then, via automatic handling, placed on ship to steam over deep ocean trench where more automation hurls the disk off the stern with automatic launchers. There are more details, like only glass in the outer 1 mm layer of the disk to stop the alphas etc. why disk shape of this size, etc but that gives the idea.)

    Here is more on why battery swap EVs will never be more than a few percent of the cars:

    Let’s look at your typical gas station: It has at least four pumps as four people are often filling up at the same time and taking less than 3 minutes to do it. (60 fill ups per hour) Also note gasoline cars come to the gas station only about 1/3 as often as the EVs will need to, so there will be at “peak swap demand times” about 180 EVs wanting a battery swap per hour.

    Now assume, generously, that a full recharge takes only one hour. Thus, the station will need recharge connection for 180 batteries recharging in parallel, if the first battery swapped out of an EV that hour is to be recharged and available at the start of the next hour to install in the EV that just pulled into the station.

    Do you have any idea what ADDED peak power demand load on the electric grid 180 batteries recharging in an hour is (at essentially every “gas station” in town)? The EVs users will need to buy an entirely new and much more power capacity electric grid UNLESS, as I suggested in recent post 1349 there is super flywheel energy unit at each recharge station, which in some way must be paid for by the owners of EVs.

    The other alternative is that battery swap EVs never get to be more than a few percent of the total cars.

    Quote Originally Posted by universaldistress View Post
    What is your take on changing out battery fluids, or is this not feasible with current battery specs? I don't know enough about the batteries they use to power cars.
    A false idea based on ignorance of where battery energy is stored. (It is in the charged electrodes). Batteries are very different from fuel cells. For example if you replace the sulpheric acid in a lead acid battery with new strong acid that will not recharge it. In fact it will probably make it nearly impossible to recharge. The discharged battery has one plate with a lead sulphide coating - You must pass current thru it to drive that sulpher back into sulpheric acid - that will be hard or impossible to do if battery has been filled with strong acid.

    SUMMARY: Yes I am quite forward thinking, but more importantly I am knowledge about how things work and able to consider the full system implications.
    Last edited by Billy T; 03-06-11 at 01:13 PM.

  2. #1362
    Quote Originally Posted by adoucette View Post
    So do our big cities like NY, Boston, Philly, Chicago, San Fran, DC, Portland, San Diego, Atlanta etc, but like the US they also sell millions of cars each year and few adults don't own one and need one. You know Mercedes, BMW, Fiat etc...



    http://www.acea.be/index.php/news/ne...onths_in_2010/

    Arthur
    They have rail systems... between cities.

  3. #1363
    Quote Originally Posted by spidergoat View Post
    They have rail systems... between cities.
    As do we in the North East where intercity traffic and distances support rail as a viable alternative (newer high speed rail might make some slightly further distance intercity rail travel possible, at least the current admin thinks its worth investing a small fraction of the cost as seed money),

    But US geography is such that our solutions will never be the same as Europes.

    http://goeurope.about.com/od/europea...arison-map.htm

    Even so, Europe also has extensive high speed roads and airports flying between the various cities as well, and passenger miles for cars is over 10 times that of rail and intercity air is 40% greater than rail.

    Arthur

  4. #1364
    Extravagantly Introverted ... universaldistress's Avatar
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    Quote Originally Posted by Billy T View Post
    for many years I have been a strong advocate for the ONLY known-to-be-economical form of fuel cycle "carbon capture" - Namely grow sugar cane for fuel and save petroleum for plastics etc. that keeps the fossil carbon out of the atmosphere.
    It keeps it out of the atmosphere in theory only. What about sugar cane or somesuch for plastics, and fossil left where it is, though it will run out before we make that decision I fear.

    I also have been a strong advocate of nuclear power (quite possibly starting even before you were born). I have posted many times about it here including suggesting a simple, cheap, way to get rid of high level waste for in excess of 10 million years. (quick summary: it is "glassified" into disks about 30cm in diameter and 3 cm thick and then, via automatic handling, placed on ship to steam over deep ocean trench where more automation hurls the disk off the stern with automatic launchers. There are more details, like only glass in the outer 1 mm layer of the disk to stop the alphas etc. why disk shape of this size, etc but that gives the idea.)
    Is age relevant lol?

    Oh no, chucking nuclear waste in the sea seems a little bit disrespectful of life. Would you IPBM it to Mars if there was life there? I think not. So chucking it somewhere where we have no idea what lives down there?

    Here is more on why battery swap EVs will never be more than a few percent of the cars:

    Let’s look at your typical gas station: It has at least four pumps as four people are often filling up at the same time and taking less than 3 minutes to do it. (60 fill ups per hour) Also note gasoline cars come to the gas station only about 1/3 as often as the EVs will need to, so there will be at “peak swap demand times” about 180 EVs wanting a battery swap per hour.
    Money to be made there? Needs must.

    Now assume, generously, that a full recharge takes only one hour.
    In a hundred years time, who knows? 10 min recharge as you wait even sooner?

    Thus, the station will need recharge connection for 180 batteries recharging in parallel, if the first battery swapped out of an EV that hour is to be recharged and available at the start of the next hour to install in the EV that just pulled into the station.
    Cache under the ground where the tanks now reside? (also you haven't accounted for increases in range.)

    Do you have any idea what a peak power demand load on the electric grid 180 batteries recharging in an hour is (at essentially every “gas station” in town)? The EVs users will need to buy an entirely new and much more power capacity electric grid UNLESS, as I suggested in recent post 1349 there is super flywheel energy unitat each recharge station, which in some way must be paid for by the owners of EVs.
    The governments pay as part of the commitment to saving the planet. It is called road/grid tax?

    Fusion reactor in every town? In every station? (How far forward?). I am not going to say a fusion reactor in every car, it is tempting, but not altogether relevant? though would probably be electric I think.

    A false idea based on ignorance of where battery energy is stored. (It is in the charged electrodes). Batteries are very different from fuel cells. For example if you replace the sulpheric acid in a lead acid battery with new strong acid that will not recharge it. In fact it will probably make it nearly impossible to recharge. The discharged battery has one plate with a lead sulphide coating - You must pass current thru it to drive that sulpher back into sulpheric acid - that will be hard or impossible to do if battery has been filled with strong acid.

    SUMMARY: Yes I am quite forward thinking, but more importantly I am knowledge about how things work and able to consider the full system implications.
    I clearly prestated my ignorance. Does not however mean I do not understand how anything works (I know you didn't say it but i felt it was inferred?), just that I couldn't be bothered to google it before hand. If that's wrong then I accept your chastisement on that basis, despite its wider than is fair range lol.

    Wireless, pay as you go, charge as you drive.

    Charging through the ground itself using quantum-genetically enhanced smart-electrons. It is far more efficient to not carry the energy? Technology like electricity seeks the path of least resistance? except where fat-cats are involved.

    Is it more about the way things could work than how they presently work? Ingenuity isn't age related, in fact I think the solutions may most probably come from someone yet to be born.

    Internal combustion engine has to go. It's dirty, unreliable, hard to maintain, short lived, downright primitive.

    SUMMARY: Can the tide be stopped? In short electric cars are a certainty as far as I am concerned, just a matter of time. . .

    And the universe has got plenty of that, subjectively of course.

  5. #1365
    Extravagantly Introverted ... universaldistress's Avatar
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    In addition. Where are we going to grow the fuel when the world is starving in the 22nd century. Equal amounts of development required there in genetic engineering methinks.

  6. #1366
    Extravagantly Introverted ... universaldistress's Avatar
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    And I wouldn't dream of throwing the hydrogen car spanner into the engine, would I?

  7. #1367
    Please use Sugar Cane Alcohol Billy T's Avatar
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    Quote Originally Posted by universaldistress View Post
    ... In a hundred years time, who knows? 10 min recharge as you wait even sooner?...
    I doubt that when speaking of battery with twice the range of current EV batteries. Why not Google about how batteries work and learn what drives the ions towards the electrodes, what rapid charaging does to the efficiency and to the production of heat which makes temperature rise even faster and greater than the inverse of the reduction in charging time.

    If you can't learn on your own, I will upon request teach you some of this so you will understand there are physical limits (laws of physics) you need to overcome for sub 10 minute charging of a large capacity battery.

  8. #1368
    10 min recharging is not unheard of now, but it's far from ready for prime time.

  9. #1369
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    Quote Originally Posted by Billy T View Post
    I doubt that when speaking of battery with twice the range of current EV batteries. Why not Google about how batteries work and learn what drives the ions towards the electrodes, what rapid charaging does to the efficiency and to the production of heat which makes temperature rise even faster and greater than the inverse of the reduction in charging time.

    If you can't learn on your own, I will upon request teach you some of this so you will understand there are physical limits (laws of physics) you need to overcome for sub 10 minute charging of a large capacity battery.

    I meant sooner chronologically as in before 100 years has elapsed, not quicker than 10 min recharge.

    I can learn on my own (the suggestion I possibly can't is a little patronising?) but I think you could offer a more concise and quicker lesson. Sounds interesting.

    How many electrodes would be needed to increase charging time? Couldn't the amount of inlets be increased to allow a quicker charge?

    Of course this is all based on present knowledge, and if you hadn't guessed I am not really one to be limited by present levels of technology. What happens when/if the laws of physics are revised? or do you believe the laws of physics are done and dusted?

    Oh and:

    http://www.newscientist.com/article/...rue&print=true

    This seems promising?

  10. #1370
    Please use Sugar Cane Alcohol Billy T's Avatar
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    Quote Originally Posted by spidergoat View Post
    10 min recharging is not unheard of now, but it's far from ready for prime time.
    Easy in small batteries, but I said one with energy storage capacity for twice the current EV range.

  11. #1371
    Registered Senior Member Skeptical's Avatar
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    UD

    Amazing how we all have to keep repeating ourselves. Your New Scientist reference is a good one. I have posted 3 different references to rapid recharge batteries in the course of this interminably enduing thread, and have to keep repeating more, since readers refuse to believe it is possible.

    Research shows clearly that a 10 minute recharge is technically possible, and only extra development work is needed. Special recharge facilities will be required, but that is just a case in investing in the equipment. I seriously doubt that a recharge facility will cost anywhere near what it currently costs to set up a gas station.

  12. #1372
    Please use Sugar Cane Alcohol Billy T's Avatar
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    Quote Originally Posted by Skeptical View Post
    ...
    Research shows clearly that a 10 minute recharge is technically possible, and only extra development work is needed. Special recharge facilities will be required, but that is just a case in investing in the equipment. I seriously doubt that a recharge facility will cost anywhere near what it currently costs to set up a gas station.
    Here is a little quantative review of the huge cost just for new power capacity required for "battery swap" recharge (not even counting the much larger cost of all the batteries being recharged as discussed in post 1361):

    Quote Originally Posted by Billy T View Post
    {post 1248}... The EV credit is equal to the sum of: (1) $2,500, plus (2) $417 for each kilowatt hour of traction battery capacity in excess of 4 kilowatt hours. Section 30D(b)(1) limits the amount of the credit allowed for a vehicle to amounts ranging from $7,500 to $15,000, depending on the gross vehicle weight rating of the vehicle.

    Thus a qualified light car ... with 16kwh battery gets … $7,504 except max is $7,500. ...
    As battery capacity of 16KWH gives the full government subsidy and any more capacity is 100% paid for by the buyer, most EV have 16kwh battery capacity but that is less than 50 round trip mile range.

    One amp from 110Volt line for 10 minutes (1/6 hour) is 110 / 6 W hour. The amperage required to deliver (with RI^2 loses transformer and DC conversion losses neglected) is 16,000x6/110 = 873 amp. When these loses plus the internal to battery losses in this rapid rate of charges causes (they show up as a very hot battery) are included, you would need about 1000 amp service connection for each battery being charged in parallel.

    As shown in post 1363, if IC cars were replaced by EV using “battery swap” recharge with an hour for the recharge the typical small swap center (comparable to only a four pump gas station) would be recharging 180 in parallel at peak swap periods. But we are now unrealistically assuming only a 10 minute recharge time so only 30 batteries are charging at one time. Thus the amperage of a 110 volt charging line would need to be: 873x30 but normally 220 volts would be used so then the line must handle “only” 873x15 =13,091 amps.

    I.e. 10 minute charge at many small recharge centers would still be total impractical with anything like the current electric power grid, UNLESS (and probably even if) as I suggested each recharge center has super flywheel energy storage facility. Then the 24 hour average current required might be as low a 4,000 amps, which is still available only at a few locations.

    As I don’t have time now to go into the losses and thermal damage recharge of a 16KWH battery in 10 minutes would cause, for FUNDAMENTAL physics reasons, not technology limitations, and because one can learn via Google search about factors I mentioned earlier, I will defer discussion of the internal working of a battery, any battery, for a while.
    Last edited by Billy T; 03-06-11 at 07:22 PM.

  13. #1373
    Registered Senior Member Skeptical's Avatar
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    Billy

    There has never been any argument against the idea that major infrastructure reform will be needed. Yes, we know that profound changes to distribution networks are required. But these are do-able.

    Bear in mind the immensely complex and expensive infrastructure that is currently required for gas powered vehicles. The thousands of tanker trucks, trains, and ships plying the roads, rails and oceans of the world. The refineries, the gas stations and the support facilities.

    To set up infrastructure to replace all that will not be easy. It will require new electricity generation, and new electricity distribution. The actual recharge sites will be the easy bit. But when the world runs out of cheap oil, there is unlikely to be much choice.

    And no, not sugar cane ethanol. If that was as cheap and easy as you claim, it would already be the standard.

  14. #1374
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    Nonsense. Cheap and easy doesn't mean something will be a standard.

  15. #1375
    Please use Sugar Cane Alcohol Billy T's Avatar
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    Quote Originally Posted by Skeptical View Post
    Billy

    There has never been any argument against the idea that major infrastructure reform will be needed. Yes, we know that profound changes to distribution networks are required. But these are do-able.
    I was responding to this misleading statement of yours:
    Quote Originally Posted by Skeptical View Post
    ... I seriously doubt that a recharge facility will cost anywhere near what it currently costs to set up a gas station.
    I don't have accurate numbers but am quite sure, that the new high power capacity transformers*, re-wiring for at least 4,000 amp 220V service and the supper flywheel used to meet the peak recharge demand as the replacement for a small four pumps only gas station will be at least 10 times more expensive than those four pumps and the in ground tanks.

    * 4000x220 = 880,000W which with the other power demands means the transformer need just for a small filling station replacement is 1 Mega Watt rated and of course this factor of ten (or more) step up in distribution system power handling capacity reflects back all the way to the new, larger (factor of 5?) power plants needed.

    I began this recent series of post after at least three were made telling how "battery swap" recharge was the solution and have made the thread's title "dead". Also I agree that 10 minute recharge is technically feasible for Li-ion batteries in your desk top, etc. but it is much more than just "technology development" to step them up to EV battery size - probably impossible to do so without tripling the energy losses and some internal cooling system inside the battery. (I will try to find a good discussion of this scaling problem I can link to, instead of explain it.)

    Yes, if money is not a concern, many things are "do-able" but in the real world they are impossible except in insignificant scale.
    Quote Originally Posted by Skeptical View Post
    Bear in mind the immensely complex and expensive infrastructure that is currently required for gas powered vehicles. The thousands of tanker trucks, trains, and ships plying the roads, rails and oceans of the world. The refineries, the gas stations and the support facilities. To set up infrastructure to replace all that will not be easy. ...
    Hard or Easy does not matter if it is unaffordable.
    Quote Originally Posted by Skeptical View Post
    And no, not sugar cane ethanol. If that was as cheap and easy as you claim, it would already be the standard.
    It is the standard in Brazil, but the first alcohol only cars were introduce about 35 years ago and it only became the standard less than a decade ago when "flex fuel" cars were introduced. Probably then next country sugar cane alcohol becomes the standard in will be Japan. A couple of years ago a Japanese/Brazilian company was formed to build a fleet of alcohol tankers and Japan is investing heavily in the production of sugar cane and plants to process it into alcohol. (I own stock in San Martinho, the fourth largest sugar/ alcohol producer in Brazil. Its new and largest of three refiners was financed mainly by the Japanese and as I recall they get 1/3 of the alcohol produced, "forever" as repayment. I believe Japan is now requiring blending of alcohol into all their gasoline.) Japan realizes that the inflation corrected cost of petroleum production is going steadily up, but that of a crop based fuel will stay essentially constant, or drop if cellulosic alcohol can be made from the crushed cane. (It is for this same reason that plants for production of plastics form sugar cane are now in operation -200,000 tons per year from the first in Brazil. Their demand has made the alcohol slightly more expensive now than gasoline in Brazil.)

    For most of the world to convert to alcohol fueled cars will require the phase out of larger gas hog cars, great increase in telecommuting, more public transport, but these thing are both do-able and more importantly affordable. It will no doubt require much of the currently non-productive near tropical* lands to be cleared for growing cane. Most of these changes are not just "affordable" but economically more productive and/or less costly than the current system. Replacing gasoline cars with alcohol cars is probably the only way to actually reduce the release of CO2, assuming most of the electric power is generated by fossil fuels, which will surely be the case for at least three decades.
    -----------------
    *Between about +30 & -30 latitude, but with some genenetic engineering perhaps half the world’s land area, is feasible. The use of corn, a food, for alcohol production must stop.

    BTW, in the coming high cost of liquid fuel / gasoline / era, the US will deeply regret the capital invested in suburban homes and roads when it realizes it can not afford the efficient public transport and high-rises, urban neighborhood parks, etc. needed to live well in the new costly energy era. In a city well designed for the new era, most of the commuting that is done should be by elevators and public automated cars on exclusive controlled access routes. - Effectively a 2D horizontal elevator system where you punch in your desired destination get in the "autocar" and like the elevator going to your desired floor, it takes you to the standard stop quite close to your desired destination. I have several post giving the details of what a modern city is like.

    See modern city concept at: http://www.sciforums.com/showpost.ph...6&postcount=24 And post 59 in that thread for some clarifications.
    For more on the autocar system see: http://www.sciforums.com/showpost.ph...9&postcount=74
    For more about the city plan see: http://www.sciforums.com/showpost.ph...1&postcount=71
    Last edited by Billy T; 03-07-11 at 09:05 AM.

  16. #1376
    Quote Originally Posted by Billy T View Post
    I agree that 10 minute recharge is technically feasible for Li-ion batteries in your desk top, etc. but it is much more than just "technology development" to step them up to EV battery size - probably impossible to do so without tripling the energy losses and some internal cooling system inside the battery. (I will try to find a good discussion of this scaling problem I can link to, instead of explain it.)
    No need.
    It's doable today Billy without your caveats.

    http://www.arb.ca.gov/msprog/zevprog...ions/burke.pdf

    See last few pages if you just want to see how well fast charging can work based on existing battery chemistry (and I'm reasonably sure this will improve over time).

    Arthur

  17. #1377
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    There was some comment on battery changing stations being overrun with auto's changing out batteries,I'm not so sure this would be the case.I looked up the average miles driven by Americans for car and light truck the average is 10k-15k a year.Even if we take the higher 15k miles driven,that would be about 42 miles driven daily.Given the range of today's EV's (nothing impressive) the daily drivers needs would still be met,without using a changing station.

    On top of this the 8 hr working stiff who's car sits in a parking space or garage can charge their batteries while at work in essence keeping them from going to a station.

    Even if there were no charging stations at work,they still have more than enough daily battery range to get back home for a night time charge.Again keeping them from the changing station.

    Actually it's quite possible the changing stations could have less drivers populating them vs gas stations,simply cause ALL drivers have to go to a gas station to fill up.Not so with electricity.

    No doubt we need to get battery range up and I see no reason why we wont.Even if it's a whole different type of battery or power pack.

  18. #1378
    Battery changing stations are IMHO highly unlikely for quite a few reasons, but with one notable exception, and that is for inner city fleet cars/govt vehicles.

    Main reason for this not happening in the consumer world is the chicken/egg problem.
    You can't afford to build/stock a swapping/recharging station unless you get a lot of business, but since there are no swapping/recharging stations in existance no manufacturer is even considering building a car with a swappable battery.

    And for the forseeable future the absolute market of EVs is SO very small that to make the cost of building in a swapable battery as an attractive option for a car builder one would need a LOT of these swapping stations and they would have to be available in lots of cities and more importantly, between cities because the reality is the time you are most likely to need to swap a battery is on a long distance trip, which makes the economics of building/stocking those first thousands of swapping stations so unprofitable that unless the Gov stepped in and paid for it up front it would never happen, and the costs of that, compared to the relatively low benefit you get from doing so makes the entire concept a non-starter.

    The other factor is that the economics of the EV, considering the cost of the battery is so high, is based on the low cost of the fuel (electricity), but if you add in to the fuel costs the significant overhead costs of these very expensive swapping stations, the effective cost of the EV's fuel goes up.

    The actual situation is that no manufacturer is even using a common battery layout, and the batteries are not easily accessible and they are integrated into cooling systems, and often in the car in protected locations, and in multiple modules etc etc. Indeed, as battery technology continues to change the batteries will continue to change making the idea of a common swappable battery (even as the number of EVs increase) less and less likely.

    Also one problem that has not been mentioned is I don't think you can tell l the condition (capacity on full charge) of a battery unless one cycles it, and so when you got a swapped battery you really would not know the expected range. I think you could easily get a battery that was fully charged, but did not have a lot of capacity and thus get yourself stranded prior to reaching the next swap point.

    Finally, as pointed out a few posts back, fast charging is already quite feasible, and in roughly the same time it takes to pump gas, and the costs of a re-charging station are far less than a swapping station and every EV can be handled, not just a select few making the economics much better, so it's much more likely that the industry will embrace this means of making EVs more practical then swapable batteries.

    Arthur

  19. #1379
    Please use Sugar Cane Alcohol Billy T's Avatar
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    Quote Originally Posted by adoucette View Post
    No need.
    It's doable today Billy without your caveats.
    http://www.arb.ca.gov/msprog/zevprog...ions/burke.pdf... Arthur
    The last conclusion of your link is: “Fast charging of both titanate oxide and iron phosphate lithium chemistries appears to be feasible.” This appears to be based on this test:

    Altairnano’s Titanate oxide electrode Li-ion 11 Ah cell was tested thru five cycles with 66amp charging for 10 minutes, 14+ seconds until the terminal voltage was 2.8V and then discharged at 12Amp rate. During charge the cell temperature rose by 4.5 degrees C which is about what I would expect for a small cell with high surface to volume ratio.

    A 16Kwh EV battery (standard to get the full $7,500 EV car subsidy) would require 1,455 of these cells, which might be assembled in a quasi-square array with 39 rows. Row 1 containing 38 cells in a line, Row 2 with 39 cells, Row 3 with 38 cells…etc. I.e. there are 20 odd numbered rows with 37 cells each and 19 even number rows with 38 cells each. 20x37 + 19x 38 = 740 +722 = 1,462 cells.

    The square flat top and bottom surface of this array is the same as the top and bottom area of the single cell but the cooling surface of the four sides of this battery package is only 4x39DH, where D is the diameter (or width= depth) and H is the height of the single cell, but both D & H will drop out when I compare the surface available for cooling of the array to the single cell. The heat produced in these 1462 cells will be to first order just 1462 times greater than the heat which produced the 4.5C temperature rise in the test of a single cell.

    If the cooling is passive thru the sides, then the temperature rise will be approximately 4.5x1462 / (4x39) = 6579 / 156 = 42 C, which if it does not immediately destroy the battery pack will greatly increase its internal resistance, causing the efficiency to drop very much and of course the heat generation per cell to rise rapidly in a positive feedback system during the 10 minute charging period and that destroys the battery pack before the 10 minute charge is completed.

    Your link in no way refutes this. I will admit my conclusion is wrong if a full size 16Kwh battery package can be charged in 10 minutes and survive a 100 full charging cycles. (Less than half a year of use.)

    I have always agreed that small single cells can be charged in 10 minutes and admitted that an internal cooling system (flowing water in thin “radiator like” plates between each row of cells?) could permit a 16Kwh battery to be charged in 10 minute, but a simple, compact, parallel / series connection of say 1,400 cells is not possible to fully charge in 10 minutes.
    Last edited by Billy T; 03-07-11 at 11:34 AM.

  20. #1380
    I believe your math is flawed.

    Each cell reaches 4.5C higher but that doesn't imply that you multiply that by the number of cells, that's a fixed amount per cell.
    The amount of additional rise in a cell is simply the percent decrease in the available surface area to radiate out the heat, but remember they didn't do anything to cool the pack during these tests. So, to overcome the gains due to being in a pack you simply need to do something like puttiig a set of aluminum tubes to act as a heat exchanger between the rows of cells and use a bit of forced air flow and to keep the heat gain per cell to a reasonable limit. Indeed, a battery recharger could be accompanied by a small cooling unit that could circulate very cold air through the battery pack during recharging.

    Arthur

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