DIY battery packs

I want to try making some battery packs for everything from old roombas to a DIY battery bank for my laptop and everything in between.

So far I have tried taking 3 dead Ni-MH battery packs from a trio of dead first gen roombas I got for free to see if I could get one semi-functional pack by selecting the least-dead cells and rebuilding them into a new pack. (long story short, it almost worked; the initial start-up was too much current to handle, but I'm pretty sure if I could have reprogrammed it to stagger the higher power motors startup sequence, it would have been able to run for at least a few minutes)

One thing I learned from that first experience was that for a space sensitive environment, just soldering the cells together isn't gonna cut it. No matter how careful I was, the joints were too fat and I had to cut away part of the external casing to get the cells to fit back inside. I also had trouble getting the solder joints to actually stick to the terminals of the cells, so had to use lots of large globs and more heat than I would have liked to get it to work at all. I'm also guessing that the solder joints create a less than ideal electrical contact, leading to increased resistance and thus limiting the maximum current the pack would have been able to provide.

I've noticed that in every battery pack I've ever taken apart, it looks like the cells are joined together with some kind of "contact weld" (no material is added, but it fuses the two pieces of metal together, I don't know if that's the right word for it. see pic related) What I want to know is what is this kind of electrical contact called, and whats the name of the tool I need to make them myself? Also, does the buss bar/ribbon connecting the cells need to be anything special?

>>TLDR: What is the name of the tool used to make this (pic related) kind of electrical connection in battery packs, and is there anything else I should know before buying one and going to town making my own packs?

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  1. 4 weeks ago
    Anonymous

    It's called a battery solderer

    • 4 weeks ago
      Anonymous

      Eh you'll also need nickel strips and lithium batteries I forgot the name 18550 or something

    • 4 weeks ago
      Anonymous

      its called a spot welder. Google it.

      wait really? Its that simple? Huh.

      Is there a reason why they seem to usually use 4 contact points? Would more produce a more efficient pack at the expense of manufacture time, or would it just be a bigger pain in the ass to take apart later?

      Eh you'll also need nickel strips and lithium batteries I forgot the name 18550 or something

      Like pure nickle? Is it some kind of alloy or something that has a specific name I can get on ebay or amazon?

      https://i.imgur.com/5tyeAtz.jpeg

      as the posters above me have indicated there is a specific tool and material to make this happen. I can't believe you are such a complete moron you would heat up a cell enough to solder it traditionally. Enjoy your chemical fire.

      These were not lithium cells, they were Ni-MH cells, which as far as I can tell have a MUCH higher tolerance for dumb-assery than lithium. Plus they were old and discharged, and their energy density is much lower (although I realize that chemical reactions other than the intended charge/discharge cycle could have in theory been initiated) I did take the risk of fire or explosion into account however. I was careful not to heat the entire cell or anything of course, and would always stop and let them cool completely if even the top part of the cell started to get warm. (as opposed to just the cap/terminal at the top) I also had a fire extinguisher on hand that was rated for chemical and electrical fires, just in case.

      • 4 weeks ago
        Anonymous

        >Four spots
        Spot welders require two points of contact for current to flow. The current does not go through the battery for self-explanatory reasons. Four is probably for redundancy.

  2. 4 weeks ago
    Anonymous

    its called a spot welder. Google it.

  3. 4 weeks ago
    Anonymous

    as the posters above me have indicated there is a specific tool and material to make this happen. I can't believe you are such a complete moron you would heat up a cell enough to solder it traditionally. Enjoy your chemical fire.

    • 4 weeks ago
      Anonymous

      soldering them with tinned tabbing wire and a light touch is actually pretty workable. It's been a common method for diyers for years.
      Obviously if you overheat the cell too much, you're going to have a bad time

    • 4 weeks ago
      Anonymous

      It's pretty hard to make a lithium cell go into thermal runaway just from soldering. Downside of soldering is very high risk of at least somewhat accelerated battery degradation.

      [...]

      wait really? Its that simple? Huh.

      Is there a reason why they seem to usually use 4 contact points? Would more produce a more efficient pack at the expense of manufacture time, or would it just be a bigger pain in the ass to take apart later?

      [...]
      Like pure nickle? Is it some kind of alloy or something that has a specific name I can get on ebay or amazon?

      [...]
      These were not lithium cells, they were Ni-MH cells, which as far as I can tell have a MUCH higher tolerance for dumb-assery than lithium. Plus they were old and discharged, and their energy density is much lower (although I realize that chemical reactions other than the intended charge/discharge cycle could have in theory been initiated) I did take the risk of fire or explosion into account however. I was careful not to heat the entire cell or anything of course, and would always stop and let them cool completely if even the top part of the cell started to get warm. (as opposed to just the cap/terminal at the top) I also had a fire extinguisher on hand that was rated for chemical and electrical fires, just in case.

      4 contact points are enough. You're not expected or supposed to take apart a spot welded pack either way. Good quality nickel strips are almost pure nickel, but there's also shittier nickel plated steel.

      While I'm making a thread for DIY battery packs, I would love to hear anybody else's experience doing something similar. Everything from tips and tricks to where to source usable (if not great condition) cells on the cheap, interesting project ideas, etc, etc.

      One thing that I have an interest in is trying to make a sodium-ion battery pack for something, rather than using lithium cells. From what I have heard, Na-ion could be a game changer in at least some applications.
      (Im going from memory so take it with a grain of salt)

      Pros:
      1) INSANE charge/discharge cycle rating (in the range of 1000's to 10,000's of cycles potentially, compared to a few 100's for lithium)

      2) Dramatically more stable and less likely to burn/explode. I've seen videos of guys hammering a nail through (what they claim is) a sodium-ion cell with no explosive results, and not catching fire.

      2a) I also got the impression that they are much more forgiving when it comes to charging/discharging them. Like if you charge them too aggressively they are much less likely to burn/explode, but not 100% sure about that.

      3) Similar nominal cell voltage curve to lithium cells, so can be used almost* as a drag and drop replacement for most existing battery applications * see cons #2

      3) Virtually identical manufacturing process to lithium cells, so much so that existing battery factories can literally use it as a drag and drop replacement with little to no modification of infrastructure

      4) (have the potential to be) less expensive than lithium cells, as sodium is MUCH more common on earth than lithium and is available in industrially suitable concentrations in far more places. (either salt mines or evaporating it out of sea water) This also helps make them somewhat less ecologically damaging than lithium cells. Although it still uses other metals that can be expensive or require ecologically harmful extraction, at the very least the lithium component of that is eliminated

      (Cons in next post)

      Brand new cells are so utterly cheap now that there are very few use cases for used garbage cells. I'm surprised you're willing to write this much about battery technologies while being wrong about most of the technicalities. The use case for sodium will be stationary storage, where currently lithium iron is far more cost efficient and offers about the same performance, if not better.

      • 4 weeks ago
        Anonymous

        >I'm surprised you're willing to write this much about battery technologies while being wrong about most of the technicalities.

        I'm just excited about a "new battery technology" that seems like it could actually be a viable option and is also going to end up being cheap. But also part of why I wrote that much was to see how much of it is actually true. Wikipedia gives you lots of numbers and chemistry, and data sheets give you lots of too-detailed info about one specific product, and advertisements and youtube videos often overhype stuff. I kind of want to get a bead on how likely it is for this to become a thing. I do still recognize that they will probably be mostly used for stationary storage though.

        >Brand new cells are so utterly cheap now that there are very few use cases for used garbage cells
        Really? I thought they were fairly expensive. At one point I vaguely remember looking at the cost of making a new battery pack for a dewalt power tool or a laptop or something and it really wasn't going to save that much money buying new cells myself, but maybe that's changed.

    • 4 weeks ago
      Anonymous

      Don't listen to that guy, you can solder batteries with a regular stick welder, just crank it to the max and do a single touch.

      • 4 weeks ago
        Anonymous

        This sounds just crazy enough to possibly work...

  4. 4 weeks ago
    Anonymous

    While I'm making a thread for DIY battery packs, I would love to hear anybody else's experience doing something similar. Everything from tips and tricks to where to source usable (if not great condition) cells on the cheap, interesting project ideas, etc, etc.

    One thing that I have an interest in is trying to make a sodium-ion battery pack for something, rather than using lithium cells. From what I have heard, Na-ion could be a game changer in at least some applications.
    (Im going from memory so take it with a grain of salt)

    Pros:
    1) INSANE charge/discharge cycle rating (in the range of 1000's to 10,000's of cycles potentially, compared to a few 100's for lithium)

    2) Dramatically more stable and less likely to burn/explode. I've seen videos of guys hammering a nail through (what they claim is) a sodium-ion cell with no explosive results, and not catching fire.

    2a) I also got the impression that they are much more forgiving when it comes to charging/discharging them. Like if you charge them too aggressively they are much less likely to burn/explode, but not 100% sure about that.

    3) Similar nominal cell voltage curve to lithium cells, so can be used almost* as a drag and drop replacement for most existing battery applications * see cons #2

    3) Virtually identical manufacturing process to lithium cells, so much so that existing battery factories can literally use it as a drag and drop replacement with little to no modification of infrastructure

    4) (have the potential to be) less expensive than lithium cells, as sodium is MUCH more common on earth than lithium and is available in industrially suitable concentrations in far more places. (either salt mines or evaporating it out of sea water) This also helps make them somewhat less ecologically damaging than lithium cells. Although it still uses other metals that can be expensive or require ecologically harmful extraction, at the very least the lithium component of that is eliminated

    (Cons in next post)

    • 4 weeks ago
      Anonymous

      Cons:
      1) Less energy dense than lithium cells, both by weight and volume. I want to say they have something like ~75% the capacity of the same sized lithium cell. (its possible and even likely that their energy density will improve with further research and development, but they will probably never be quite as good as lithium for energy density by weight simply because sodium is a heavier element. Even so, I feel like a 25% drop in capacity is acceptable in many applications in exchange for cheaper cells and much longer lifetimes)

      2) Slightly different voltage curve compared to lithium, necessitating the use of charge/discharge controllers either specifically designed for sodium cells, or charge/discharge controllers that can distinguish between the two and alter their behavior appropriately. Aside from potential safety/cell health and longevity issues from possibly using the wrong voltage curve, a laptop for example that is assuming it has a lithium battery pack that is instead fitted with a sodium pack would incorrectly predict how much power is left in the cell.

      3) Currently more expensive than lithium cells. This however is purely because they are currently less common and so economy of scale hasn't yet driven their price down. If I remember correctly there is at least one (possibly more) major cell manufacturer who is either retrofitting an existing factory to produce sodium cells or is building a whole new facility to produce sodium cells.

    • 4 weeks ago
      Anonymous

      My only experience with salvaging NiMH cells for an out of production Ryobi battery pack was that shortly after combining the best of two into one more cells died and it was pointless work. I was charging them separately in a NiMH cell charger to see which ones charged and held.

      • 4 weeks ago
        Anonymous

        It wasn’t pointless if you learned something.

        Welding them is a meme. I’ve soldered all mine without problems, just don’t take 5 minutes with a 300 w stained-glass iron.
        I’ve had a few with some trouble wetting on the endcaps, but eventually got a good connection.
        If you don’t want to solder them, just buy them with tabs already on them.
        > that’s a thing?
        Yeah, baby.

    • 4 weeks ago
      Anonymous

      They are already out. They’re about like NiCd cells, but could be even less cycles at this point.
      NiCd has roughly double the cycles of li-ion.
      More than double the high-discharge rate li-ion cells.
      Only advanage might be Na vs Li. But a lot of them are doped with cobalt, mercury, or whatever anyway so you’re not going to sprinkle the dead battery contents on popcorn.

    • 4 weeks ago
      Anonymous

      Wow.
      >10k+ cycles
      Highly debatable. As of right now, not gonna happen.
      >more stable and less likely to burn/explode
      >you saw some guy hammering nails through it
      So you did see it explode? It still evaporates itself full power on contact with oxygen, a danger for everyone around it, just doesn't turn into greek fire nightmare fuel anymore. If it didn't explode, it was a fake so-ion to begin with.
      >3
      Yeah, no.
      >4
      Should've been 1). Still it will never be mined from sea water due to contamination. Maybe some cheap chink shit will do, but at that point you get what you pay for.
      >Somewhat less ecologically damaging
      It's literally every environmentalists wet dream right now. If it's even close to viable at scale, expect it to be mandatory for most larger, immobile applications.

      At least you got the come mostly right.

      • 4 weeks ago
        Anonymous

        >So you did see it explode? It still evaporates itself full power on contact with oxygen

        It did not explode or burn. Also its not contact with oxygen, its contact with water that makes alkali metals explode/burn. They rip apart the water to bond with the oxygen, releasing hydrogen gas and heat in the process, leading to fire or explosion, depending on rate of reaction.

        As for if it was a fake cell, its certainly a possibility, but I still want to believe. Besides, you dont have to be able to shove a spike through it for it to be more stable or robust than lithium cells.

        • 4 weeks ago
          Anonymous

          Frick off. This isn't PrepHole.

      • 4 weeks ago
        Anonymous

        >it will never be mined from sea water due to contamination.
        Can't they separate pure NaCL salt out of sea water (as opposed to having other metals or salts in there) by using various kinds of electrolysis or other chemistry shenanigans? And besides, isn't rock salt just sea salt from ancient oceans, and so would have more or less the same contamination in it? I would think the hard part would be getting pure NaCl, because then its just whatever process they use to crack the sodium off of it.

        They probably can get some useful byproducts at the same time too, mostly magnesium or other stuff like that if I had to guess

        • 4 weeks ago
          Anonymous

          Frick off, moron. Yes, we know you were just pretending.

          • 4 weeks ago
            Anonymous

            Frick off. This isn't PrepHole.

            What's the problem here? Like did I say something offensive? I genuinely don't understand why you're so mad. (I'm assuming this is the same person but I could be wrong, if so I apologize, but my question still stands)

  5. 4 weeks ago
    Anonymous

    I also just kind of enjoy hacking stuff together for the hell of it. I dont vape, but I have a collection of them that I found on the ground to harvest their batteries in the eventual hope of making something useful out of it. Also have a more or less brand new dewalt battery pack with one or two bad cells out of like 8 or 10 (cant remember off the top of my head) that could be turned into a regular capacity pack instead of the double capacity with 2 banks of series cells connected in parallel, or something else.

    I sometimes idly day-dream about designing some kind of abomination that contains an assortment of Ni-Cad/Ni-MH AA, AAA, etc cells, individual lithium cells of various sizes, full battery packs (like a 20V dewalt pack, greenworks 40V packs, old 18V black&decker packs, hell even 12V lead-acid batteries, and uses 1 or more arduino's and other supporting circuitry and a shit ton of buck/boost converters to create outputs suitable for a number of different laptops, USB power, maybe even AC output.

    I've already made a contraption that takes a shit ton of rechargeable Ni-MH AA cells in series and parallel and regulates it to the voltage one of my laptops need, and its connected to a snipped off charging cable from a dead wall adapter for it. It actually works, but I'm still slightly scared of it, cause I have no clue what is a safe current draw for a AA Ni-MH cell.

    • 4 weeks ago
      Anonymous

      >I sometimes idly day-dream about designing some kind of abomination that contains an assortment of Ni-Cad/Ni-MH AA, AAA, etc cells, individual lithium cells of various sizes, full battery packs (like a 20V dewalt pack, greenworks 40V packs, old 18V black&decker packs, hell even 12V lead-acid batteries, and uses 1 or more arduino's and other supporting circuitry and a shit ton of buck/boost converters to create outputs suitable for a number of different laptops, USB power, maybe even AC output.
      Pretty sure there's a mental illness for that and you can get medication that is covered by your insurance.

      • 4 weeks ago
        Anonymous

        lmao

        >Four spots
        Spot welders require two points of contact for current to flow. The current does not go through the battery for self-explanatory reasons. Four is probably for redundancy.

        So one electrode would go on top of the nickle strip, and the second is on the surface of the battery right? I would think if you had both electrodes on the nickle strip it would carry all the current through the strip and not bond with the cell terminal at all...

        • 4 weeks ago
          Anonymous

          >I would think if you had both electrodes on the nickle strip

          You peaked my curiosity enough to watch part of a vid where he does this. Of course he might be clueless.

          • 4 weeks ago
            Anonymous

            No. No matter where the electricity flows, the tip (point of contact) is where most heat is happening. The current flows for a fraction of a second, never enough for the tab or the cell to even get warm to the touch.

            there was a "cold weld" trend a while back where a carbon fiber semiconductive tip was split s.t. when you touched metal it would get super hot very quick from the short but you could pull it off and put it on your thumb and the tips would be cool.

        • 4 weeks ago
          Anonymous

          No. No matter where the electricity flows, the tip (point of contact) is where most heat is happening. The current flows for a fraction of a second, never enough for the tab or the cell to even get warm to the touch.

  6. 4 weeks ago
    Anonymous

    Also, is it worth buying a spot welder, or is it worth getting a bunch of super capacitors or something and building my own? Will I be better off just buying one?

    Roughly how much is a good amount to spend on one of these things?

  7. 4 weeks ago
    Anonymous

    >NOOO YOU CAN'T SOLDER IT IT WILL ESPLODE

    Skill issue, sixtyfiveford moggs all of diy.

    • 4 weeks ago
      Anonymous

      This guy says that he goes to stores that take batteries to be recycled, do you happen to know what kind of store does that? Or other good source of free/cheap cells?

      It's pretty hard to make a lithium cell go into thermal runaway just from soldering. Downside of soldering is very high risk of at least somewhat accelerated battery degradation.
      [...]
      4 contact points are enough. You're not expected or supposed to take apart a spot welded pack either way. Good quality nickel strips are almost pure nickel, but there's also shittier nickel plated steel.
      [...]
      Brand new cells are so utterly cheap now that there are very few use cases for used garbage cells. I'm surprised you're willing to write this much about battery technologies while being wrong about most of the technicalities. The use case for sodium will be stationary storage, where currently lithium iron is far more cost efficient and offers about the same performance, if not better.

      >Brand new cells are so utterly cheap now that there are very few use cases for used garbage cells.
      Where are you buying these from? Like ebay, amazon, alibaba?

      • 4 weeks ago
        Anonymous

        any scrapper takes batteries. hardware and auto part stores usually take them also. they get paid for recycling them though, so they won't hand them over for free. I have seen battery recycling bins at various shops, including electronic shops, and nobody seems to be watching those very closely.

  8. 4 weeks ago
    Anonymous

    most spot welders are too large and 'pinch' the material between electrodes on each side of the work piece. you need a battery spot welder specifically, with the smaller electrodes beside each other. they sell them on Amazon for like $20. I'm sure you could PrepHole one yourself, they are pretty simple devices.

    • 4 weeks ago
      Anonymous

      >I'm sure you could PrepHole one yourself, they are pretty simple devices.

      Yeah I thought about that. Probably the safest way to do it would be to buy a bunch of super capacitors and have them just dump current after charging up for a minute or however long it takes them. I've seen someone make the pinch kind with a microwave transformer too. That might be cheaper, but while I am reasonably competent with electronics, I'm not good enough to bet my life on my work, so I'm not messing with microwave transformers for now cause I dont want to fricking die lol. I figure I might buy one of the $20-$35 ones on ebay/amazon and see if they do the trick, cause thats not that much in terms of up front cost.

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