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Thread: Chevy Bolt cell specs?

              
   
   
  1. #1
    Senior Member T Rush's Avatar
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    Chevy Bolt cell specs?

    oddly, I just don't find the individual pouch cell info on the web...maybe I'm just not using the right Google

    but I have been able to piece tidbits from here-n-there together, then throw some weak maths at it
    ....tell me if you think I'm close


    basics
    http://media.chevrolet.com/media/us/...1-bolt-du.html
    Battery system preliminary specifications include:

    60 kWh lithium-ion battery pack.
    288 lithium ion cells
    Five sections
    10 modules
    96 cell groups – three cells per group
    960 lbs. (435 kg) total weight
    so for amp hours per cell I get:
    60,000wh / 288cells = 208.33...
    208.33 / 3.8v = 55ah
    dang! thats hardcore for a single pouch cell
    ...and it gets better when you consider the size and weight

    then weight
    960 lbs. / 288cells = 3⅓ lbs. (about 1Ĺ kg)
    ...so thats using the total battery pack weight; which might include the car's floor structure, massive cooling plate, bms system, and all the other stuff and junk?
    but even at that high est. weight, that seems close to the density of 18650 and 2170 Tesla cells?? wut

    here is web confirmation
    https://cleantechnica.com/2016/02/14...a-deeper-look/
    The specific energy numbers are:

    Bolt............ 0.138 kWh/kg
    Model S.......0.156 kWh/kg


    The Bolt pack is described as having 96 cell groups with 3 cells per group. At an average voltage per cell of 3.8 volt (V), the pack voltage consisting of 96 cells in series is about 365V. With a pack energy capacity of 60 kWh, and three cells in parallel per group, each cell has a rating of about 55 amp-hour. From the description of high nickel and manganese content and low thermal sensitivity, it is likely that this is a variation of the nickel-manganese-cobalt-oxide chemistry, NMC, an excellent choice for electric vehicle applications.
    https://cleantechnica.com/2016/09/03...e-one-another/
    Push EVs notes, “the Chevrolet Bolt EV battery is made with 288 (3p96s) LG Chem cells, each cell is rated at 55 Ah and 3.75 V. I’m not sure about the 55 Ah capacity, but this is what I was told a year ago by a LG Chem worker. This represents a total of 59.4 kWh (288 x 55 Ah x 3.75 V). The battery volume is 285 L and the mass is 435 kg, this means an energy density of 208 Wh/L and 136 Wh/kg at the battery level, not cell. The Chevrolet Spark EV battery is made with 192 (2p96s) LG Chem cells, each cell is rated at 27 Ah and 3.75 V. This represents a total of 19.44 kWh (192 x 27 Ah x 3.75 V). The battery volume is 135 L and the mass is 215 kg, this means an energy density of 144 Wh/L and 90 Wh/kg at the battery level, not cell.”
    size:
    "GM says that each battery cell is 3.9 inches (100 mm) high and 13.1 inches (338 mm) wide"
    ....they look kinda thick, and judging by the video I saw where a guy tried to take the modules out of a wrecked Bolt, it looked like the 3p spacing takes up at least two or more inches
    these are the only photos I can find of a pouch cell(but I guess I didn't look at all the Internets)
    https://nickelinstitute.org/en/Nicke...ChevyBolt.aspx
    Improved power and energy
    “You usually have a battery cell that delivers either the desired levels of energy or power, but not traditionally both. With this cell design and chemistry we were able to deliver a battery system with 160 kilowatts of peak power and 60 kilowatts hours of energy,” said Gregory Smith, Bolt EV battery pack engineering group manager.

    The cells are arranged in a “landscape” format and each measures in at only 100mm high and 338mm wide providing improved packaging underfloor. The lower profile cell design enabled the vehicle structure team to maximize interior space.

    anyway....I've been looking at just about every other battery option: size, weight, and price; to get the power I'm after for my little eMotard Derbi build I want to do...and still keep coming back to the recovered Leaf modules for simplicity and low price(vs a bunch of used 18650 cells out of a Tesla, which might cost more and be a pain with all those little suckers. tho get me back to my target 'closer to stock' bike weight) then even thought long and hard about eBay Lithium Titanate 11ah and 3.5ah but I doubt I'll be able to take advantage of faster charging and likely they will end up weighing and costing more(unless I build a smaller pack than I have to with the Leaf's), or some other SPIM08HP lithium polymer; but with those options I'd have to build a pack in both serial and parallel, and bms(so the Leaf modules already have that, and don't really need a bms)
    ...but now I'm thinking about tacking down that guy who posted the video yesterday that said the Bolt 'blocks' wouldn't work for him, and he'd sell them...or still, even at $1000 for 30 of these cells off eBay(and this might be the guy from the video) is more than I'd need(figure I'd just need 18 to 20 in series, and those would stack up in my narrow Derbi frame nicely!) and save some weight and size for about the same price as Leaf's, if these pouch cells can be taken out of those modules?

    Last edited by T Rush; 25 March 2018 at 0441. Reason: eh, might be too much of a hassle for me to do

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    Senior Member Stevo's Avatar
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    Hmmm... IF these modules can be opened up and cell pouches removed and re-assembled in series, you would only need 6 modules to get a 72v pack at 54 aHr, equivalent to about 9 Nissan Leaf modules. Thats a big IF. If the tabs are soldered together in the 3p configuration, I dont know how hard it would be to unsolder the tabs to separate the pouches without damaging anything. I haven't seen anybody tried that surgery yet.
    BUT, if the surgery can be successful, that would work well for your Derby conversion.

    I did find this informative blog on the older generation of Chevy ev packs. Maybe helpful:
    http://www.schultzengineering.us/delta-11-12.htm
    Last edited by Stevo; 25 March 2018 at 1157.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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    Senior Member T Rush's Avatar
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    they are still that nominal about 3.8 voltage...so 18 to 20 of them needed for a 72v system, right?

    those tabs look spot welded together in two areas of each tab...at worst you would have to cut those spots out, leaving a double notched "W" tab
    ...i think it would still be enough tab left to DIY connect a single line of them in series

    don't know how much of a 'destructive method' of deconstruction would be required to get the cells out, but I'm better at taking things apart than putting them back together(hehe) as witnessed by how many of 'my projects' have taken up semi-permanent residence in boxes(sigh)....still connecting 20 of them together end to end then zig-zag folding them into a stack pack would be a bunch easier than doing a 20s20p combo of four hundred 18650 cells(and taking all those out of a Tesla pack)

    dang it, I just need my wad of cash burning a whole in my pocket from selling my other motorcycle...or maybe its good that I dont have that moneys yet or I might of leaped a few times on different odd ideas like this already


    if we would use a 'ballpark' price for a 7.6v 55ah Leaf module of $50 to $100 and 8Ĺlbs each, and say we do a 10 pack battery
    ... thats 85lbs 76v 55ah $500~$1000
    but if a 30 cell module of these is $999 on eBay; then each cell is $33 for 3.8v 55ah and 3lbs, but you need twice as many at 20s
    ... thats 60lbs 76v 55ah $666
    so its safely in the lower third of the price ballpark, and almost a third of the weight savings
    [for reference:]
    [a used eBay 18650 Tesla 20s20p cell pack of 400 might weigh alittle less @ maybe 50 lbs but cost twice as much at $1400]
    [the eBay SPIM08HP cell pack of 140 in 20s7p for the same ~ 72v 55ah would be @ 90 lbs and still $1400 specs link ]
    [then with the 2.4v eBay Lithium Titanate 11ah cells you would need 30s5p to do that same battery with 150 of these cells for the same $1400 but @ 122 lbs]
    Last edited by T Rush; 26 March 2018 at 0232. Reason: added more eBay battery cell types for reference

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    Check out these Weber videos. Lots of info, dimensions and weights of 10s3p, and 8s3p modules. The steel tray the batteries sit in is 143.5# of those 960#. The 10s3p modules are about 137.5# each, and the 8s3p modules are about 123.5# The 10s3p module is about 13.5" x 37.75" x 4.25"

    https://www.youtube.com/watch?v=ssU2mjiNi_Q&t=263s

    https://www.youtube.com/watch?v=ZBzRKglr95U&t=2450s

    https://www.youtube.com/watch?v=VUvAW6skwrA&t=4s

    There are two pouch cells per "cassette", as the GM engineer calls the thin aluminum boxes they are in. So the three cells that have their tabs spot welded together are in different boxes, meaning you will probably need to pull out three "cassettes" at a time.

    https://youtu.be/sLFOxgBDuB8?t=82
    Last edited by Warren; 25 March 2018 at 1918.

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    Senior Member T Rush's Avatar
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    yeah, I'd watched parts of those videos....but didn't make it far enough to see that he weighed and measured the 5 battery sections
    thanks for pointing that out....I also watched more this time and saw where Dr. Kelly talked about construction related to taking a unit apart any further
    Quote Originally Posted by Warren View Post
    ... The 10s3p modules are about 137.5# each, and the 8s3p modules are about 123.5# The 10s3p module is about 13.5" x 37.75" x 4.25"
    I thought those are for the 'sections'...which are two 10s3p modules together or a 10s3p and 8s3p module together....not one of the 10 modules individually

    the eBay seller lists a 10s3p module at 65lbs
    ...so using that and/or Dr. Kelly's weights of 137.5 lbs. for a 60 cell section(10s3p + 10s3p) and 123.5 lbs. for a 54 cell section(10s3p + 18s3p)
    I calculate each pouch cell weight at under 2.2 lbs....and thus my 20s Derbi 72v Bolt pack might only weigh around 50 lbs.



    Quote Originally Posted by Warren View Post
    ...
    There are two pouch cells per "cassette", as the GM engineer calls the thin aluminum boxes they are in. So the three cells that have their tabs spot welded together are in different boxes, meaning you will probably need to pull out three "cassettes" at a time.
    also watched all of that video....and just had assumed the GM engineer meant to say 'three cells per cassette'....but you are correct, I went back and counted 15 cassettes in a 10s3p module, so there are two per cassette
    Last edited by T Rush; 26 March 2018 at 0355. Reason: I didn't really edit this post, much, yet

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    Moderator Nuts & Volts's Avatar
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    The individual pouch cells are definitely welded together at the tabs. Check out the picture more closely on eBay. I do not think youíll want to reconfigure from the current pack configurations. Well itís not a simple task at least.

    Keep in mind that in the car these cells are only being pushed to 2.5-3C max. Thatís not very much. Iím hoping they are good for 5C or so, but can not find any data either. To that regard the Tesla modules are better for power density right now. Iíd test them, but donít want to spend $800 to do it.

    They are more like 3.65V nominally. (350V listed by GM/96) not 3.8V as well. Iíve never seen a lithium cell with 3.8V as nominal despite what retailers list them at.

    Iíve seen some speculation on Bolt forums that they individual cells may be 63-65Ah at full capacity and 55Ah is just the usable. No hard data just speculation.



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    Quote Originally Posted by T Rush View Post

    I thought those are for the 'sections'...which are two 10s3p modules together or a 10s3p and 8s3p module together....not one of the 10 modules individually

    the eBay seller lists a 10s3p module at 65lbs
    ...so using that and/or Dr. Kelly's weights of 137.5 lbs. for a 60 cell section(10s3p + 10s3p) and 123.5 lbs. for a 54 cell section(10s3p + 18s3p)
    I calculate each pouch cell weight at under 2.2 lbs....and thus my 20s Derbi 72v Bolt pack might only weigh around 50 lbs.

    Good catch! You are absolutely right. We will hit 10K miles on our Bolt this week. There is someone in Fredericksburg at 51K miles! I've got seven Leaf modules on my cargo bicycle. I wish the Bolt modules were as easy to deal with.

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    Senior Member T Rush's Avatar
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    Quote Originally Posted by Nuts & Volts View Post
    ...


    Keep in mind that in the car these cells are only being pushed to 2.5-3C max. That’s not very much. I’m hoping they are good for 5C or so, but can not find any data either. To that regard the Tesla modules are better for power density right now. I’d test them, but don’t want to spend $800 to do it.


    They are more like 3.65V nominally. (350V listed by GM/96) not 3.8V as well. I’ve never seen a lithium cell with 3.8V as nominal despite what retailers list them at.


    I’ve seen some speculation on Bolt forums that they individual cells may be 63-65Ah at full capacity and 55Ah is just the usable. No hard data just speculation.


    interesting....well, if the voltage is lower per cell, I could just add another cell to make up for it?

    ...that 55ah as 'usable' and really the cells are bigger sounds even more awesome tho

    I've read that the new 2170 Tesla cells are really just about the same as the old 18650 cells, just alittle bigger so maybe slightly cheaper to make and you'd need a few less(important if you need and have to make as many as Tesla does).... but how old is the 18650?...I mean the more I look into batteries, motors, and controllers; it seems like almost nothing new has happened in the last 10years! maybe only with production cost coming down and more available....like I'll find a 'new' motor to research and I'll find where someone bought one in 2009 for $50 less

    its like I used to build computers, as that was really the only way to stay on top of the latest tech and prices....as if you bought a big name manufactured computer; in the time they took to design it, have the parts made, built it, shipped it, you read about it in a monthly magazine, looked at it in the store, waited in line to check out, drove it home, opened the box, set it up and turned it on: it would be out of date and/or over priced compared to the thing they we're gonna release next week
    ....so I could just order the latest greatest online(or the good stuff that dropped in price) stick a few new parts in every year(or build a whole new PC every 18months~2years for someone else) and hand down my old stuff....then awhile ago I stopped; after years of being caught up in that race, and 'having to' make constant improvements to keep them running smooth, it'd just seemed like the computers had gotten good enough, so some of mine are over 4 years old and still doing fine
    ....I'm wondering if EV tech hasn't already stalled like that?!?....seems like the Tesla cells are a mess, and all someone needed to do was build a much larger single cell(not the 2170, which is just about the same deal again) that has close to the same weight and performance, and I'm wondering if this is it


    yeah but....I don't know about "c rate" yet....I'm just starting to grasp that
    Last edited by T Rush; 26 March 2018 at 0829. Reason: added the quote

  10. #9
    Senior Member T Rush's Avatar
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    Quote Originally Posted by Warren View Post
    Good catch! You are absolutely right. We will hit 10K miles on our Bolt this week. There is someone in Fredericksburg at 51K miles! I've got seven Leaf modules on my cargo bicycle. I wish the Bolt modules were as easy to deal with.
    yeah? so you like the Bolt?

    my Wife has the Leaf(two year lease was cheaper than buying)....I was trying to talk her into getting a Model 3 next
    ....but now the more I read about the Bolt's battery, I might see if she would get one of those...esp. because the Leaf sucks for range in the winter when it gets cold, and they didn't fix that for 2018, where the Bolt has really good battery cooling and heating, maybe even better than Tesla?....and Iowa can easily have 120į difference between summer and winter temps
    Last edited by T Rush; 26 March 2018 at 0830. Reason: hmmm, maybe the lease on the Nissan is 3 years

  11. #10
    Senior Member Stevo's Avatar
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    Dont knock the Tesla cells design... They are basically a smaller, flattened out pouch cell rolled up to conserve space (simplified). I mean it makes perfect sense to roll up a flat volume into a cylinder configuration. Now if they were the size of a Headway cylinder instead of a AA flashlight battery, I would be more swayed to utilize them. I like the size and shape of the pouch type cells just because its so much easier to build a pack. I didn't catch the 2 cells per cassette, I thought there were three. I wonder if you drilled a hole through the spot weld to separate, then it would be easy to align the holes and bolt the tabs together with a small piece of Al added for support/strength. Thats how I'm going to connect the tabs to my Kokam pouches.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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