Results 1 to 16 of 16

Thread: Learjet's dodgy DIY powerwall made from used laptop batteries

  1. #1
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default Learjet's dodgy DIY powerwall made from used laptop batteries

    Hi guys, I've gone and jumped on the 18650 battery DIY powerwall band wagon. Most of these 18650 batteries come from old and/or used laptop batteries. To harvest the cells out of a laptop battery, I very carefully remove the plastic case by bashing the shit out of it on the cement until it smashes into pieces. Then I pull all the wiring off the cells so they don't short out. The cells are then cleaned up ready for testing. I use an Opus charger / discharger to test for capacity. If the cells are 1800mAh or better, show no sign of self discharge and don't get hot in the test process, they go into the powerwall.

    The battery holders are screwed onto wood to hold them together. Yes, wood had to be part of this somehow. However the bus bars are insulated from the wood by rubber spacers. Each cell holder is fused with glass axial 2A fuses. If a cell goes short circuit, the fuse blows. The two trays I presently have contain 120 cells in a 3s40p configuration, or 12V 80Ah (11.1 volt nominal). They are charged by solar panels with a 3 cell lithium ion controller. Cell balancing is done with a passive cell balancer.

    The battery holder design allows me to easily swap out worn out cells for more gooderer ones without the need to unsolder anything, theoretically giving this contraption an unlimited life span. So far so good, I haven't blown myself up.... yet.











  2. The Following 15 Users Say Thank You to Learjet For This Useful Post:

    + Show/Hide list of the thanked

    admin (25-12-17),allover (23-12-17),croozer (30-01-18),efab (23-12-17),gordon_s1942 (23-12-17),Keith (25-12-17),mandc (23-12-17),mtv (23-12-17),SS Dave (23-12-17),station-rat (23-12-17),Tiny (23-12-17),tristen (23-12-17),Uncle Fester (24-12-17),vnboost (23-12-17),william10 (23-12-17)



Look Here ->
  • #2
    Administrator
    mtv's Avatar
    Join Date
    Jan 2008
    Posts
    19,885
    Thanks
    7,504
    Thanked 15,043 Times in 6,759 Posts
    Rep Power
    5636
    Reputation
    238845

    Default

    Very impressive, mate!

  • #3
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Thanks MTV. It's an alternative to lead acid batteries for off grid use.

  • #4
    Administrator
    mtv's Avatar
    Join Date
    Jan 2008
    Posts
    19,885
    Thanks
    7,504
    Thanked 15,043 Times in 6,759 Posts
    Rep Power
    5636
    Reputation
    238845

    Default

    Quote Originally Posted by Learjet View Post
    Thanks MTV. It's an alternative to lead acid batteries for off grid use.
    And more importantly, recycling/re-purposing a lot of still-useful cells, many of which may have made their way into landfill.

  • The Following User Says Thank You to mtv For This Useful Post:

    Learjet (23-12-17)

  • #5
    Crazy Diamond
    Tiny's Avatar
    Join Date
    Dec 2010
    Location
    Tasmania
    Age
    64
    Posts
    6,388
    Thanks
    10,991
    Thanked 5,432 Times in 2,649 Posts
    Rep Power
    2152
    Reputation
    88977

    Default

    Very impressive!
    I'll bet you scratched around trying to get the colours grouped & still had some odd ones, must be killing you. lol
    Cheers, Tiny
    "You can lead a person to knowledge, but you can't make them think? If you're not part of the solution, you're part of the problem.
    The information is out there; you just have to let it in."

  • #6
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Quote Originally Posted by Tiny View Post
    Very impressive!
    I'll bet you scratched around trying to get the colours grouped & still had some odd ones, must be killing you. lol
    Yeah it's a bit difficult to colour coordinate when Sony, Panasonic, Samsung and LG all use different colours.

  • #7
    LSemmens
    lsemmens's Avatar
    Join Date
    Dec 2011
    Location
    Rural South OZ
    Posts
    10,573
    Thanks
    11,853
    Thanked 7,053 Times in 3,334 Posts
    Rep Power
    3149
    Reputation
    132432

    Default

    Looks like a lot of hard work, What is the current capacity of the system? I'm wondering how long they'd take to discharge under load?
    I'm out of my mind, but feel free to leave a message...

  • The Following User Says Thank You to lsemmens For This Useful Post:

    xapi (27-12-17)

  • #8
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Quote Originally Posted by lsemmens View Post
    Looks like a lot of hard work, What is the current capacity of the system? I'm wondering how long they'd take to discharge under load?
    It's a lot of work but I wouldn't call it hard.

    Capacity is just under 1kW at 960Wh. A load of 20 amps for 4 hours would flatten them (average of 500mAh per cell), to 3V per cell on average for a 2000mAh cell. Some cells are a little more, some less but 2000mAh is the average. Being used batteries (some NOS) they have to be treated kindly as cell resistance increases with age. Each cell was tested at a constant discharge rate of 500mAh so all cells should be safe at that rate. 0.5A x 40p = 20 amps, so that's about as fast as I would discharge the whole array. For short periods they could handle double that. 80 amps is the absolute max as the 2A fuses would start to blow after that.

  • #9
    Premium Member

    Join Date
    Jan 2008
    Posts
    4,311
    Thanks
    5,979
    Thanked 4,171 Times in 1,771 Posts
    Rep Power
    1348
    Reputation
    50392

    Default

    Very impressive indeed, Learjet!

    I certainly wouldn't call it 'dodgy'.

    I counted a total of one hundred and twenty individual cells in the cabinet. Is that correct?

    Where did you get the used laptop batteries from? A friendly, local computer repairer?

  • The Following User Says Thank You to tristen For This Useful Post:

    Learjet (24-12-17)

  • #10
    Senior Member
    Uncle Fester's Avatar
    Join Date
    Jan 2008
    Location
    Commonly found in a pantry or the bottom of a fridge, searching for grains, fermented or distilled
    Posts
    6,400
    Thanks
    2,288
    Thanked 4,412 Times in 2,516 Posts
    Rep Power
    2044
    Reputation
    81738

    Default

    You could have saved a lot of work using these :


    Which is one of my projects right now. Still waiting for the solar charger that can deal with this and more batteries. In total 4.6kWh for a 4kW inverter for one powerpoint chain. Then if all goes well I will do another.

    Cycle life with 18850's is usually 500 but you might be able to double it if you set the charge controller to 4.1V max instead of 4.2-4.25V. So for the cost of 10% less usable capacity you get twice as many cycles.
    Deep cycling down to 3V (under load) is not a problem. Usually they still have 10% charge left. Panasonic go down to 2.7V and less, but strictly avoid that also because you are mixing cells.
    Of course most of yuor cells probably have used those cycles but the good thing about Li- is that they still then have 80% capacity unlike the Lead-Acid scam that just dies. After another 500 cycles you might still have 50%.
    I like your copper pipe rails.
    What kind of BMS are you using?
    Last edited by Uncle Fester; 24-12-17 at 11:08 AM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

  • The Following 5 Users Say Thank You to Uncle Fester For This Useful Post:

    admin (25-12-17),efab (25-01-18),Keith (25-12-17),Learjet (24-12-17),xapi (27-12-17)

  • #11
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Quote Originally Posted by tristen View Post
    ...

    I counted a total of one hundred and twenty individual cells in the cabinet. Is that correct?

    Where did you get the used laptop batteries from? A friendly, local computer repairer?
    Yep, 120 cells. Small by DIY powerwall standards. There's a guy in Brisbane with 40kWh!

    Cells came from friends, computer repair shops, the recycle yard and a mate that works at a school in the IT department.


    Quote Originally Posted by nomeat View Post
    You could have saved a lot of work using these :

    ...

    What kind of BMS are you using?
    Thanks nomeat. More work = less cost. The old cells cost me zero, though I did buy 4 new ones. Most of the rest I had on hand. Probably cost me less than $50 all up to make.

    Some of these cells are new old stock. They wouldn't charge in a laptop, but once taken out and brought up to voltage slowly they sprang back to life. Be interesting to see how many cycles I get out of them. I don't discharge very deep and they usually sit around 4.15V at max charge. I plan to change out cells as the old ones get weak. How this will all work out I don't really know. It's an experiment. At least it didn't cost me much.

    I use a small capacity controller with balancing function for a passive BMS. It works surprisingly well on this number of cells but there's one guy using similar on a 20kWh system! He uses a few that overlap.



    You'll have to keep us up to date with your lifepo4 bank.

  • The Following 3 Users Say Thank You to Learjet For This Useful Post:

    admin (25-12-17),tristen (24-12-17),Uncle Fester (24-12-17)

  • #12
    Senior Member
    Uncle Fester's Avatar
    Join Date
    Jan 2008
    Location
    Commonly found in a pantry or the bottom of a fridge, searching for grains, fermented or distilled
    Posts
    6,400
    Thanks
    2,288
    Thanked 4,412 Times in 2,516 Posts
    Rep Power
    2044
    Reputation
    81738

    Default

    Quote Originally Posted by Learjet View Post
    Probably cost me less than $50 all up to make.
    Definitely can't beat that


    Discharge deep (3.0V) is better than going over 4.1V. If you limit at 4.0V they will last even longer.

    Cells that were stored below 2.7V may have developed dendrites.
    These dendrites pierce the insulator between the electrodes and are ticking time bombs.

    Yes, was planing on making a Nomeat's Dodgy Powerwall thread with all the details once I get started.

    ...and then maybe one day Nomeat's Uberdodgy electric wooden garden tractor but that could take a while to master
    Last edited by Uncle Fester; 24-12-17 at 12:35 PM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

  • #13
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Well definitely got a few time bombs in there then! Hope the individual cell fusing saves me. And the CID.

    I've seen photos of a working wooden tractor in action. But it wasn't electric. It was IC. I want one!

  • #14
    Senior Member
    Uncle Fester's Avatar
    Join Date
    Jan 2008
    Location
    Commonly found in a pantry or the bottom of a fridge, searching for grains, fermented or distilled
    Posts
    6,400
    Thanks
    2,288
    Thanked 4,412 Times in 2,516 Posts
    Rep Power
    2044
    Reputation
    81738

    Default

    Quote Originally Posted by Learjet View Post
    Well definitely got a few time bombs in there then! Hope the individual cell fusing saves me. And the CID.
    Just keep the whole contraption away from the house, definitely not inside the house.
    Do not have too much trust in the cell 'fuses'. The short will be inside that starts the thermal runaway, the plus cap blows off like a bullet and flames shoot out and will start heating up the cells in front in your case.

    Here is how I am mounting my 18650's for a 12V (3S) project:




    The batteries are in spacer kits (pretty cheap on Ebay) and if a cap blows there is nothing in the way(will be in a metal storage box) for the flames to ignite or for the caps to short out and no chain reaction with other cells. It is mounted on a piece of fibro.

    That roll of tin band will be laid out in strips across the spacers and the batteries will be soldered with wire cuttings I have collected from 1/4watt resistors.


    I've seen photos of a working wooden tractor in action. But it wasn't electric. It was IC. I want one!
    We really should be neihbours. You do the wood work and I do the electromechanics
    The plan ATM will have 4 x 14"hubmotor wheels (4WD) + 2 motors for the detachable slasher + servo motors for the excavator/plough. Top speed 6km/h but 160Nm immediate torque with the power equivalent of two horses
    Solar charged LiFePO4 of course.
    Last edited by Uncle Fester; 24-12-17 at 02:37 PM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

  • #15
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Quote Originally Posted by nomeat View Post
    ...
    We really should be neihbours...
    We would get into too much mischief.

    I've used those cell holders before. Made up a small 3s6p for the front door and a 12s4p for the electric bike. They are very compact. Not as easy to replace a cell though.

    I think I'll be right with these 18650's. They will be treated very carefully and constantly monitored. Probably safer like this than in a laptop.

  • #16
    Senior Member
    Learjet's Avatar
    Join Date
    Jan 2008
    Location
    Queensland
    Age
    61
    Posts
    1,454
    Thanks
    650
    Thanked 1,203 Times in 391 Posts
    Rep Power
    564
    Reputation
    15945

    Default

    Now have three racks of 60 used laptop batteries = 180 batteries (3s60p), 120Ah, 1440 watt hours of colourful lithium POWER!!! Probably should have arranged wiring better for photo lol.

    Last edited by Learjet; 25-01-18 at 04:08 PM.

  • The Following 2 Users Say Thank You to Learjet For This Useful Post:

    station-rat (26-01-18),tristen (25-01-18)

  • Bookmarks

    Posting Permissions

    • You may not post new threads
    • You may not post replies
    • You may not post attachments
    • You may not edit your posts
    •