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Thread: I want a power tool Li-ion pack with removable cells!

  1. #1

    Default I want a power tool Li-ion pack with removable cells!

    Someone needs to 3D print battery packs that have regular spring-loaded cell holders, so when one cell in your $100+ pack fails, you can fix it easily !

    How do you take apart spot welded cells, anyway?

  2. #2
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Manufacturers wouldn't allow it. Everything has to be idiot-proof. Imagine the dumbest person you know; that's who they have to design stuff for. Individual cells are simply too unsafe for morons. They'd short them, burn themselves, and then sue the company for a brain transplant. No major manufacturer is going to take that risk. You're stuck buying a new $100 proprietary pack from them.

  3. #3

    Default Re: I want a power tool Li-ion pack with removable cells!

    The source of your problem is trying to use discarded scrap cells.

    Start with top notch brand new cells, wired properly they will wear evenly.

    When capacity is below 70-75% of what it was when new, discard/recycle them all as a set and replace.

    Disassembling properly welded packs is hard work and does damage a fair proportion of cells.

    There are no-weld solderless pack building solutions but they are bulkier and not cheap.

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    Flashaholic* adamlau's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    I have disassembled packs from DeWalt/Makita/Ryobi/Milwaukee/Bosch and more and wired up a harness to discharge the pack via an RC charger (beyond what using the tool could accomplish) in order to reduce the potential energy store before disassembly. The work is not difficult, but you must take precautions. This was a post I made around twelve years ago when I vented a cell during my first pack disassembly . I eventually refined my technique and used ceramic shears and insulated pliers with silicone sleeves to roll back the contact strips while cutting. Not a single vent across a dozen packs afterwards. You can always visit a local battery shop and have them replace the cells for a small fee.
    Last edited by adamlau; 11-25-2020 at 05:04 PM.

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    *Flashaholic* idleprocess's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by lumen aeternum View Post
    Someone needs to 3D print battery packs that have regular spring-loaded cell holders, so when one cell in your $100+ pack fails, you can fix it easily !
    In addition to the liabilities - operational and legal - associated with user-replaceable cells, I do not believe such solutions will reliably deliver the kinds of current that power tool packs can. Spot-welding the connections makes for a highly reliable connection with almost zero contact resistance.

    Quote Originally Posted by lumen aeternum View Post
    How do you take apart spot welded cells, anyway?
    As others have mentioned, it's effectively surgery and not without risk.
    I apologize that this letter is so long; I did not have time to write a short letter

  6. #6
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Milwaukie and Rigid have boards managing and balancing cells in their packs. It not just thrown together in series/parallel combos. High current is needed in heavier application for these tools.

    Leave them alone

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    Flashaholic* turbodog's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by adamlau View Post
    ... wired up a harness to discharge the pack ...
    Slightly off topic, but the safety angle makes me mention this anyway.

    If you want to discard a single cell or an entire pack safely... put it in a container of cold water with some salt added. Will safely discharge everything while keeping temps low. We have a 5 gallon bucket just for this at the local RC facility.
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by turbodog View Post
    Slightly off topic, but the safety angle makes me mention this anyway.

    If you want to discard a single cell or an entire pack safely... put it in a container of cold water with some salt added. Will safely discharge everything while keeping temps low. We have a 5 gallon bucket just for this at the local RC facility.
    Doesn't that just make it impossible to recycle?

    Okay, to be fair, recyclers probably just throw most stuff out anyway. It's a feel-good policy.

  9. #9

    Default Re: I want a power tool Li-ion pack with removable cells!

    No you **must** discharge to dead flat for safety before giving to a recycler

    The materials get extracted for creating new cells if done properly, but you're right, still very much in infancy

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    Flashaholic* DIWdiver's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    It sounded to me like the OP wanted an after-market/DIY solution, so the MFR is out of the loop, and liability/safety issues are in the hands of the consumer, as they are with almost all DIY endeavors.

    Keeping this in mind, I would say yes, that's a great idea, but since there are dozens, maybe hundreds of different battery packs either in production or at the point where they need to be re-celled, and the fraction of owners who would be not only able but inclined to print and assemble a new pack is pretty miniscule, it would be impractical to ask that there be, in general, printable designs for any given tool. While you might get lucky and stumble across the fanatic who was willing to spend the dozens or hundreds of hours required to design and perfect a particular pack, the likelihood of finding someone wanting to do your particular pack is pretty small.

    I did re-cell a 14.4V NiMH pack years ago, and the process was so difficult that I decided that I would never do it again. Designing and printing a new pack to incorporate easily replaceable cells would be so far beyond that level of difficulty that it's hard to imagine anyone ever undertaking such a project without significant financial backing. While such a project could be crowd-funded, I doubt that you could raise much money to develop a printable battery pack for a (insert your mfr and model here).

    This is all on top of the practical issues raised earlier in this thread. The resistance of coil springs makes them completely unusable in power tool applications. Leaf springs might work in less demanding applications, but still cannot even compare to welded tabs. Soldered or welded connections are the only practical means to pull 10A or more from a cell with minimal voltage loss.

    I'm sure that some vape devices pull currents like this from cells without soldered or welded connections, and I'm sure I'll catch some flack from people who know about the specifics of these devices. We'll deal with that if it comes up.

  11. #11

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by DIWdiver View Post
    Soldered or welded connections are the only practical means to pull 10A or more from a cell with minimal voltage loss
    I completely disagree.

    Sure if you define "practical" narrowly enough.

    Alternatives just haven't been demonstrated yet for this particular use case.

    I really do not see 3D printing as essential to a solution, other than prototyping.

    But then I also would not value trying to duplicate the various form factors

    nor care about the cordless tool use case specifically all that much.

    But there are plenty of high C-rate solderless no-weld projects out there in the eBike / EV world

    their implementation from a business / distribution POV have not been great

    but the technology is there, and more and more options will emerge over the next few years.

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    Flashaholic* turbodog's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by john61ct View Post
    I completely disagree.

    Sure if you define "practical" narrowly enough.

    Alternatives just haven't been demonstrated yet for this particular use case.

    I really do not see 3D printing as essential to a solution, other than prototyping.

    But then I also would not value trying to duplicate the various form factors

    nor care about the cordless tool use case specifically all that much.

    But there are plenty of high C-rate solderless no-weld projects out there in the eBike / EV world

    their implementation from a business / distribution POV have not been great

    but the technology is there, and more and more options will emerge over the next few years.
    Aren't the ebikes using lipo flat cells that already have handy tabs built in?
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    Flashaholic* turbodog's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by WalkIntoTheLight View Post
    Doesn't that just make it impossible to recycle?

    Okay, to be fair, recyclers probably just throw most stuff out anyway. It's a feel-good policy.
    Not that I know of. And yes, plastics are being trashed from the recycle waste stream, but lithium, nickel, etc found in batteries is very much in demand.
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  14. #14

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by turbodog View Post
    Aren't the ebikes using lipo flat cells that already have handy tabs built in?
    No, the majority buy or build spot-welded packs assembled from cylindricals.

    Some designs not so tight on space douse the flat "pouch cells".

    The term LiPo is most often used for the multi-cell packs from the RC world, crazy high power density but most liable to go boom

  15. #15
    Flashaholic* turbodog's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Then my vote is that practical packs with user-swappable cells (likely 18650) are not going to happen. The high current needed heats the springs making contact with the cell ends and destroys their springiness, not to mention the damage to plastics from a red-hot spring.

    I have seen flat braided heavy gauge wire going to cell terminals before, with a spring applying pressure. But this gets back to "practical" again. It's expensive, bulky, and a pain to deal with.
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  16. #16

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by idleprocess View Post
    In addition to the liabilities - operational and legal - associated with user-replaceable cells, I do not believe such solutions will reliably deliver the kinds of current that power tool packs can. Spot-welding the connections makes for a highly reliable connection with almost zero contact resistance.
    Can't imagine any legal problems with modifying something I own.
    Resistance & contact when dropped might be an issue - not when using the pack for a stationary lantern though.
    But flashlights with high amp draw do use a spring, so that is solvable.
    At worst, use a set-screw to push a flat plate into contact with the battery, and/or a clamp over the battery so it does not dislodge if dropped.

    WRT the logic board - the board must have wires that go to the battery pack, and they can be spliced/soldered into the replacement battery holder in the same configuration. Might be possible to 3D print a battery holder that attachs to the bottom of the original unit, so you don't have to print the upper part that goes into the tool.

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  18. #18
    Flashaholic* turbodog's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    I actually looked through 6-8 of the links you sent.

    Few observations:

    1. They are all talking about the same problems brought up in this thread already.
    2. Power tool batteries also need the pack to be compact and very rugged if dropped.
    3. Etc.

    Not saying it's not possible, simply not realistic and economically a net loss.
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  19. #19
    *Flashaholic* idleprocess's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by lumen aeternum View Post
    Can't imagine any legal problems with modifying something I own.
    The legal problems will be on the manufacturer's side were they to provide packs with removable non-welded cells. Someone blowing up their hand using mismatched cells is almost an inevitability. And even if they cannot successfully litigate, the damage to the brand will be very real as they cry on social media everywhere and get news coverage.

    Quote Originally Posted by lumen aeternum View Post
    Resistance & contact when dropped might be an issue - not when using the pack for a stationary lantern though.
    This is a decent use case. And there have been modders and tinkerers a-plenty that have rebuilt power tool packs using high-density cells for such purposes - i.e. ~3C-capable cells slotted into a Ryobi ONE+ pack ought provide decent runtime on their 150W inverter - just don't try to run a drill or saw with that pack.

    Quote Originally Posted by lumen aeternum View Post
    But flashlights with high amp draw do use a spring, so that is solvable.
    They're generally not pushing the kind of amps a power tool draws, and any stepdown or resistance at peak amps isn't as noticeable with a flashlight as it is a power tool one might routinely run at 90% of rated load. Also - outside of the occasional 'spring bypass mod', flashlights pretty much always use coil springs so there's a lot less A/B to compare to than there would be an OEM power tool pack verses a 'no spot weld' rebuilt pack.

    Quote Originally Posted by lumen aeternum View Post
    At worst, use a set-screw to push a flat plate into contact with the battery, and/or a clamp over the battery so it does not dislodge if dropped.
    As has been mentioned, there are solutions out there for the hobbyist - they're just less practical for power tool battery packs than rebuilding them with a spot-welder or soldering iron.

    Quote Originally Posted by lumen aeternum View Post
    WRT the logic board - the board must have wires that go to the battery pack, and they can be spliced/soldered into the replacement battery holder in the same configuration. Might be possible to 3D print a battery holder that attachs to the bottom of the original unit, so you don't have to print the upper part that goes into the tool.
    There are dozens of files on sites like thingiverse that replicate parts of power tool battery housings and adapt them to other purposes - such as slotting into other makes of tool. But note that all such files I've come across are 'drop-in' replacements for OEM that assume you will be welding the cells together.

    For all the effort you seem willing to put into this, it seems like procuring - or obtaining access to (i.e. vis-à-vis a makerspace) - a battery spot-welder will provide superior results at a lower cost with less risk once one masters the skills of pack disassembly and re-welding cells.
    Last edited by idleprocess; 11-27-2020 at 01:29 PM. Reason: ++content, proofreading
    I apologize that this letter is so long; I did not have time to write a short letter

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    Flashaholic* DIWdiver's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    The e-bike and powerwall applications are quite different from power tool applications, particularly in the cell current. Does anyone ever build a powerwall that can be drained in 20 minutes or less? Or an e-bike that needs to be charged every 20 minutes? No.

    In general the cell currents of these devices are intended to be between c/1 and c/30, maybe even less. In power tools the cell currents are (at high load) between 3C and 10C, maybe higher.

    So the power tool pack requires a much lower resistance connection to the cell than the other applications require. Thus solutions that work well for powerwalls and e-bikes don't necessarily work well for power tools.

    I'm not saying it's impossible to build a power tool pack with replaceable cells, I'm just saying I haven't yet seen a practical solution.

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    Flashaholic* DIWdiver's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Hey, vaping products draw huge currents from 18650 cells that are replaceable. What do they do?

  22. #22

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by idleprocess View Post
    There are dozens of files on sites like thingiverse that replicate parts of power tool battery housings and adapt them to other purposes - such as slotting into other makes of tool. But note that all such files I've come across are 'drop-in' replacements for OEM that assume you will be welding the cells together.
    I have not found any - the search function on the sites I've looked at is dismal. For instance, I have Craftsman tools from the Nicad days, and I'd like to find a "connector" that will let me attach Ryobi packs.

    Is it possible to deduce the bad cell without disassembling? If so, you could sometimes remove & replace just the one cell without so much work. Or at least just one sub-assembly of the x-Series, y-Parallel array?

    How else can you continue to use the good cells from a pack? Even if you cut the cells apart, how do you make a cell with a piece of sharp steel welded to both ends suitable for inserting into a flashlight? Maybe using adapters that fit into C or D size lights, so the edge of the metal that overhangs the diameter of the cell won't touch anything? Goop it up with liquid electrical tape?

  23. #23

    Default Re: I want a power tool Li-ion pack with removable cells!

    Thanks for the gratitude for putting my time in trying to help, not.

    But will soldier on.



    Quote Originally Posted by lumen aeternum View Post
    Is it possible to deduce the bad cell without disassembling?
    Once a group of cells is connected in parallel, you cannot know anything about the individual members without atomizing them

    except for gross mishaps like internal shorting, but no one who knows what they're doing would let their cells get close to such an event.



    Quote Originally Posted by lumen aeternum View Post
    How else can you continue to use the good cells from a pack?
    The original top quality brand new cells used by the OEMs pretty much wear evenly.

    So if you have 500 scrapped cells, even if 100 of the "test OK" as most people know how to

    they are still going to be very close to EoL for a high C-rate use case.

    Accurate cap testing is done with a precisely timed CC dummy load, good ones $800+ cheap versions maybe $150, super cheap and still precise possible if you're very clever.

    ESIR testing is only good comparing the same cell before vs after.

    _______
    For a variety of tool makes, I would design a pack carried on the belt, and focus on connectors only into the various tool pack form factors

    Reco Andersons

    eBikes by the way routinely go to very high rates in peak stress conditions, even if they only average 2-3C continuous.

    Rigid parallel plates, say aluminum dipped into a robust dielectric coating, or with an FRP liner

    compression bolts between the cells

    Poron at 3-5mm for some "springiness"

    Crimped pure-copper swage terminating marine spec wires

    WAGO busses for changing the xPyS coltage /Ah layout as needed

    Maybe BMS while in use for LVC, but hobby chargers can handle precise balance charging

    No soldering or welding needed, when performance drops

    atomize the lot run cap tests for go/no-go and reassemble

    But personally I would start with top quality brand new cells myself.
    Last edited by john61ct; 11-28-2020 at 12:47 AM.

  24. #24

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by lumen aeternum View Post
    Even if you cut the cells apart, how do you make a cell with a piece of sharp steel welded to both ends suitable for inserting into a flashlight?
    You rip the welded strip off the ends if the cell completely

    A certain percentage will be damaged.

    A Dremel can restore the end to flat, kinda.

    IMO more trouble than it's worth, if you put any value on your time.

  25. #25

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by john61ct View Post
    The source of your problem is trying to use discarded scrap cells.
    No, the problem is the charger saying my $80 pack is faulty, after only maybe 50 charge cycles. So I want to replace the single bad cell with a new one. But I probably have to cut all the cells apart to FIND the bad one. Then I want to clamp them together again after replacing the bad one.

  26. #26

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by lumen aeternum View Post
    No, the problem is the charger saying my $80 pack is faulty, after only maybe 50 charge cycles. So I want to replace the single bad cell with a new one. But I probably have to cut all the cells apart to FIND the bad one. Then I want to clamp them together again after replacing the bad one.
    If the C-rate is very high, plenty of cells will only last 50 cycles

    not at all likely there are just a few bad cells

    more likely a few just reached EoL a dozen cycles ahead of the rest.

    Unless you are prototyping a business idea, or just love messing around with this stuff for fun, just buy a new pack, as best quality as possible not off brand.

    If you do love messing around with this stuff, buy the DIY spotwelder at ES and some nickel-plated copper strips and go for it!

  27. #27

    Default Re: I want a power tool Li-ion pack with removable cells!

    N.E.S.E modules

  28. #28
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    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by john61ct View Post
    If the C-rate is very high, plenty of cells will only last 50 cycles
    No, that's way too few cycles, unless the cells are being driven way over spec. And any reputable manufacturer is not going to run cells out-of-spec. For high power applications, they use high-drain cells, like a Sony VTC5A or better.

    Of course, if the battery pack is a fake or a OEM replacement, then all bets are off and maybe 50 cycles is possible.

  29. #29
    Flashaholic* turbodog's Avatar
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    Default Re: I want a power tool Li-ion pack with removable cells!

    It's anecdotal, but after decades of r/c racing (surface, water, and air) my experience is that good cells/packs (nicd/nimh/lipo/li-ion) will handle massive discharges w/o damage and will certainly last >50 cycles. I also abuse an 18v drill running a 6" hole saw... no problems so far. The milwaukee packs have a temp sensor in them but will supply tons of power till the pack overheats.
    This is your life, and it's ending one minute at a time.
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  30. #30

    Default Re: I want a power tool Li-ion pack with removable cells!

    Quote Originally Posted by WalkIntoTheLight View Post
    if the battery pack is a fake or a OEM replacement, then all bets are off and maybe 50 cycles is possible.
    Yes.

    My main point is, if a pack built from new identical cells fails, it is **very** unlikely that any of the cells are in great shape,

    good enough for a high-C discharge use case for an extended period of time

    to justify the effort required to to what OP is talking about.

    But then, different people value their time differently some simply can't afford to work with new cells, and others see tinkering with this stuff as a fun hobby in and of itself.

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