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Thread: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

  1. #61
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Well now we will never be able to bore Surefire at 20mm diameter....jk
    Interesting stuff, before you know it the xyz lithium battery will be the new D battery

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    It will be very interesting to see discharge tests of another new Panasonic batt NCR20650A 30 Amp rated. Notice this "650"

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by JB007Rules View Post
    Maybe for the consumer market this is true since they are all thin and light... This isn't true AT ALL for the commercial and military market though.... I'm a managing partner at one of the largest Toughbook re-sellers in the country (Rugged Depot) and coming from 12+ years in the Panasonic Toughbook world, Panasonic OWNS the rugged laptop market and they are mostly 18650's but they are slowly going towards either 14500's or something similar to make the laptops skinnier.

    Seeing as ALL the cells are Panasonic (They invented the 18650) it's an IN for them to sell their laptops with their cells in them too

    I'd be interested to see what Panasonic can offer for these consumer grade laptops as you said they don't have 18650's in them. They are probably losing the business to Samsung or LG on those cells

    Thanks!
    If by commercial market you mean business, that is not at all true. Corporate laptops have also moved away from 18650 and other easily replaceable sells.

    The rugged market still uses them, but that's but a small portion of the overall market.

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Kurt_Woloch View Post
    As far as I know, self-balancing boards still use 18650 batteries. And currently their sales vastly outnumber sales of electric cars with millions of boards having been shipped to the USA so far. ;-)
    TESLA alone will consume 100's of millions of 18650 cells this year.

  5. #65

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by SemiMan View Post
    If by commercial market you mean business, that is not at all true. Corporate laptops have also moved away from 18650 and other easily replaceable sells.

    The rugged market still uses them, but that's but a small portion of the overall market.
    You are correct. I should have been more specific

    Thanks!

  6. #66

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Am looking forward to testing the new Tesla round cells. But there is also new e-car battery technology made in gemani going into licensed mass production

    http://www.spiegel.de/auto/aktuell/e...a-1097291.html


  7. #67
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    this is what I don't get. There is a certain number of cubic feet or inches or meters that a vehicle has for batteries. No matter what size you make the cell, the overall volume remains the same. Whether you get 4 of these or 5 of the old type, the W-hr will remain the same.

    Common sense suggests that the smaller the cell is, the more of them you will fit in the same volume. Kind of like sand can occupy the entire glass jar and large rocks half the space, with small rocks 5/8 of the space.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    The bigger the cell the less connections you need, and Tesla puts cooling pipes between the cells, maybe cylindrical cells are not as inefficient as we think.

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by etc View Post
    this is what I don't get. There is a certain number of cubic feet or inches or meters that a vehicle has for batteries. No matter what size you make the cell, the overall volume remains the same. Whether you get 4 of these or 5 of the old type, the W-hr will remain the same.

    Common sense suggests that the smaller the cell is, the more of them you will fit in the same volume. Kind of like sand can occupy the entire glass jar and large rocks half the space, with small rocks 5/8 of the space.

    nope. the empty "wasted" space between cylindrical cells is the same for any cell diameter. i.e. if you're gonna pack the maximum amount of cells in a given volume, the empty spaces between cells is the same with bigger cells and smaller cells

    but with smaller cells you get more overhead in interconnection, packaging, insulation between cells, etc

    and there's also a limit to how big you can go because a big cell would trap heat inside

    and since there are space contraints because they're building the cells into the floors of the vehicles i suppose they chose 20700 to be optimal given all the other considerations

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    I have seen and got to sit in the Tesla at their store in Houston. Pretty amazing tech. Personally, I just could not see spending that kinda money on a car that I can't go off road, tow a boat or camper with. That is just me.

    Has any ever done a cost of real world ownership analysis on one? Checking eBay a 2013 is listed around $52K. How long do battery packs last? Cost of installing a home charger station? Cost of electricity to charge vehicle? Other required services? Can a local shop do any services? Stuff I just wonder. Not counting costs, I guess I see the possibility for a big city car, but not so much a car for a young family who may travel.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Overclocker View Post
    nope. the empty "wasted" space between cylindrical cells is the same for any cell diameter. i.e. if you're gonna pack the maximum amount of cells in a given volume, the empty spaces between cells is the same with bigger cells and smaller cells
    This is directly contrary to laws of physics and basic geometry. Do you have any proof, or is this just conjecture?

    I am not convinced until you come up with the exact rating for each cell, the number of cells in say 1 cubic meter and so on.

    Here is proof via a diagram. Imagine you have one big cell in a cube, there is a lot of wasted space in the first box. 4 smaller cells waste less space and 16 smaller less still and so on, ad infinitum. The more you shrink it, the less space is wasted. A bigger cell has a higher Watt-hour rating but not enough to make up for the tons of space it wastes.

    I am not going to take time to draw a precise diagram but this gives an idea. The smaller the cell shrinks the less wasted space is generated. If you could shrink each cell to the size of grain of sand, they would almost completely occupy any given space. They wouldn't be efficient in terms of wiring and stuff. So the idea to get a 20mm cell versus 18mm is just an attempt to reduce costs of wiring and complexity, perhaps fewer failures, but it's not an attempt to increase the Watt-hours of the entire battery. At best, they will end up where they are now with less wiring.

    Last edited by etc; 07-17-2016 at 10:20 AM.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Str8stroke View Post
    I have seen and got to sit in the Tesla at their store in Houston. Pretty amazing tech. Personally, I just could not see spending that kinda money on a car that I can't go off road, tow a boat or camper with. That is just me.

    Has any ever done a cost of real world ownership analysis on one? Checking eBay a 2013 is listed around $52K. How long do battery packs last? Cost of installing a home charger station? Cost of electricity to charge vehicle? Other required services? Can a local shop do any services? Stuff I just wonder. Not counting costs, I guess I see the possibility for a big city car, but not so much a car for a young family who may travel.
    The environmental impact is the same as a gas car... because the hidden cost is you still have to charge it and use electricity and thus either coal or nuclear or something. It's just a hidden cost, plus the cost of recycling the battery.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by etc View Post
    Quote Originally Posted by Overclocker View Post
    nope. the empty "wasted" space between cylindrical cells is the same for any cell diameter. i.e. if you're gonna pack the maximum amount of cells in a given volume, the empty spaces between cells is the same with bigger cells and smaller cells ...
    This is directly contrary to laws of physics and basic geometry. Do you have any proof, or is this just conjecture? ...
    Correct. This claim was already refuted last month in this thread. Packings in a finite region (vs. infinite plane) do depend on the sizes, e.g. you get 100% density if you pack a circle into a circle of the same size, but less than that if you pack it with smaller diameter circles. Follow the link for citations.

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk




    same

    you could put 16 little circles in there and the total area would be the same. for some reason this isn't immediately obvious

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Exactly. Ratio of a circle area to a touching square area is a constant value (π/4) no matter the size they are. Now we know who was kicking butts at school instead of studying

    There is another issue: generated heat is a function of volume, but dissipated heat is a function of surface area. That is the larger the battery the more it is prone to overheating. More of that, we have no idea about the ability of Li-Ion layers to transfer heat in lateral direction (from layer to layer). So, theoretically, a large battery may be relatively cold outside, but melting in its core.
    Last edited by vadimax; 07-18-2016 at 04:03 AM.

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by etc View Post
    The environmental impact is the same as a gas car... because the hidden cost is you still have to charge it and use electricity and thus either coal or nuclear or something. It's just a hidden cost, plus the cost of recycling the battery.
    Singapore transport authority has calculated 222 g/km of CO2 emissions for Tesla S P85.

    I like Singapore
    Last edited by vadimax; 07-18-2016 at 04:17 AM.

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

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  18. #78

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Overclocker View Post



    same

    you could put 16 little circles in there and the total area would be the same. for some reason this isn't immediately obvious
    They sometimes use hexagonal packing which is supposed to be more efficient but if one thinks of it as a percentage thing then the size of a circle shouldn't matter if the pattern layout doesn't change to more accommodate the area it is set in you could think of it as looking at the same pattern through binoculars or zooming out to make the "appearance" look bigger or smaller but the wasted space doesn't change via size.
    Last edited by Lynx_Arc; 07-18-2016 at 05:51 AM.
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  19. #79
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Gauss163 View Post
    But that packing density is for packings in the infinite plane. For packings into some finite region you also need to account for the voids left at the boundaries of the region, which smaller cells will generally fill better. For example, see this page on circle packings in a square.



    from: http://powercartel.com/2015/03/used-...ules-for-sale/

    the packs are big you really shouldn't be worrying about the little voids in the ends. a smart designer could utilize that space anyway...

  20. #80
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by vadimax View Post
    Exactly. Ratio of a circle area to a touching square area is a constant value (π/4) no matter the size they are. Now we know who was kicking butts at school instead of studying

    There is another issue: generated heat is a function of volume, but dissipated heat is a function of surface area. That is the larger the battery the more it is prone to overheating. More of that, we have no idea about the ability of Li-Ion layers to transfer heat in lateral direction (from layer to layer). So, theoretically, a large battery may be relatively cold outside, but melting in its core.

    So there it is, the surface area decreases relative to the volume with overheating being a real problem.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Gauss163 View Post
    Correct. This claim was already refuted last month in this thread. Packings in a finite region (vs. infinite plane) do depend on the sizes, e.g. you get 100% density if you pack a circle into a circle of the same size, but less than that if you pack it with smaller diameter circles. Follow the link for citations.

    I do not see a refutation anywhere. I see this link which just proves the point. The latest item at the end reads 0.248 which is the highest value except for 0.250 at the top but would be interesting to see the next value.

    https://en.wikipedia.org/wiki/Circle...ng_in_a_square
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Overclocker View Post



    same

    you could put 16 little circles in there and the total area would be the same. for some reason this isn't immediately obvious
    But such tiling only works for certain regular shapes, e.g. it is not true for packing circles into circles. In any case it is a moot point since thermal constraints usually prevent use of optimal packing density configurations.

  23. #83

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Gauss163 View Post
    But such tiling only works for certain regular shapes, e.g. it is not true for packing circles into circles. In any case it is a moot point since thermal constraints usually prevent use of optimal packing density configurations.
    You can look up packing circles and if you get a large enough amount of circles then making them smaller or larger shouldn't affect the loss of size if you pack them the most efficient way which isn't this way but rather hexagonally (6 around 1) It is said this is 91% efficient and larger or smaller the 91% efficiency doesn't change if the size of the space to fill doesn't add loss around the outer edges by too large of circles I would think. It is akin to zooming in and out on perhaps 100 cells packed like this and you can perceive smaller or larger circles but the percentage of wasted space only changes on the outer edges where there isn't space enough to add a new cell but more space than normal loss between cells.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Lynx_Arc View Post
    You can look up packing circles and if you get a large enough amount of circles then making them smaller or larger shouldn't affect the loss of size if you pack them the most efficient way which isn't this way but rather hexagonally (6 around 1) It is said this is 91% efficient and larger or smaller the 91% efficiency doesn't change if the size of the space to fill doesn't add loss around the outer edges by too large of circles I would think. It is akin to zooming in and out on perhaps 100 cells packed like this and you can perceive smaller or larger circles but the percentage of wasted space only changes on the outer edges where there isn't space enough to add a new cell but more space than normal loss between cells.
    Not true. Look at any reference on circle packing in circles, e.g. this Wikipedia page. With 2 circles you get 50% density, 3 = 65%, 4,5 = 69%, 6 = 67%, 7 = 78%, 8 = 73%, 9,10 = 69%, etc, not reaching 80% till 19 circles.

  25. #85

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Gauss163 View Post
    Not true. Look at any reference on circle packing in circles, e.g. this Wikipedia page. With 2 circles you get 50% density, 3 = 65%, 4,5 = 69%, 6 = 67%, 7 = 78%, 8 = 73%, 9,10 = 69%, etc, not reaching 80% till 19 circles.
    Try this page
    https://en.wikipedia.org/wiki/Packing_problems
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Lynx_Arc View Post
    What's your point? That's the parent of the page I pointed you at and it contains only 1 sentence on packing circles in circle (a link to the page I gave - which refutes your claims).
    Last edited by Gauss163; 07-21-2016 at 06:17 PM.

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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    someone's being a square peg in a round hole. or specifically, trying to pack circles in circles when they should be packing them into rectangles

  28. #88

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Gauss163 View Post
    What's your point? That's the parent of the page I pointed you at and it contains only 1 sentence on packing circles in circle (a link to the page I gave - which refutes your claims).
    The point is when it comes down to the usage of packing batteries related to this thread they are using far more than 19 batteries to begin with which pretty much makes arguments based upon that irrelevant. With hexagonal packing there becomes a point where you have to make the circles way too big in order to negate it as the most efficient method used.
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    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Lynx_Arc View Post
    The point is when it comes down to the usage of packing batteries related to this thread they are using far more than 19 batteries to begin with which pretty much makes arguments based upon that irrelevant...
    It seems we both agree that the theoretical results have limited value in practice, and those results have now been linked for those who have interest in such, so I don't see any value in continuing down this tangent.

  30. #90

    Default Re: Tesla's gigafactory dropping 18650's and going with 20700 - per Elon Musk

    Quote Originally Posted by Gauss163 View Post
    It seems we both agree that the theoretical results have limited value in practice, and those results have now been linked for those who have interest in such, so I don't see any value in continuing down this tangent.
    Well it was an interesting (and enlightening) exchange nevertheless. I think the one issue on cell size that is perhaps important is the height difference as we can agree the diameter (in these large packs) isn't going to have much of an affect on power of the battery but rather the 2mm increase in height or about 11% and this will translate into that much more power if the energy to volume ratio of 20700s match 18650s which I believe they will be about the same. I think it all depends on how you stack the batteries in the end if they vertical then unless the pile is 10 high (for 18650s) then changes in height would happen but at 10 cells high that would equal 9 high of the 20mm cells so you essentially save the expense of 1 less layer of batteries in your pack now how much this equates to cost of the pack isn't known (labor + parts) and how much the 20700s per cell cost would be. If these battery packs cost lets toss a number of $8k at it and equate 11% cost reduction (1 layer) that would make the cost 7120 for a pack with the same amount of power our perhaps 880 dollars a car cheaper to produce and replacement battery costs would be passed onto customers (at least some of the savings). As for % cost of the car itself.. that much on most of these electric cars (Tesla) is minimal but if they start to make $20k electric cars or somehow even $15k electric cars then the difference in price becomes more apparent.

    If they started making devices (lights, etc) that use the 20700 size that wouldn't bother me as there would be a market for sleeves and spacers to use 18650s in those devices so you wouldn't have a lot of useless batteries around. I think if the major 18650 market takes a nosedive because of these competing batteries (20700) that instead of having major battery makers producing multiple capacities/amps of cells we could see offerings diminish down to limited varieties of them and cost go up after they change over and sell of their excess inventory. The uses of 18650 for the sake of most here are devices that IMO don't have a great incentive to be loyal to the battery size once another size takes front stage so power banks and flashlights and stuff they will just start making new ones that take 20700s if that is the prominent type.
    Last edited by Lynx_Arc; 07-22-2016 at 02:29 PM.
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