4 ms·

Just curious: if you wanted to do something like that, but prevent a... thermal event, how would you protect an experimental battery realistically? Build a bric

• mlsu 1y ago
  I think there’s not much you can do other than placing it very far away from the house. Those big packs just have way too much energy.
• louwrentius 1y ago
  A runaway NMC battery is notoriously difficult to extinguish, so the best thing to do is to not do it and investigate LFP prismatic cells instead. Many people building home storage batteries use a shed a few meters away from their home.
  • knowitnone3 1y ago
    what's a NMC battery?
    • yurishimo 1y ago
      Nickel manganese cadmium maybe?
    • jonesjohnson 1y ago
      Nickel Manganese Cobalt - a type of Lithium battery chemistry https://en.wikipedia.org/wiki/Lithium_nickel_manganese_cobalt_oxides https://en.wikipedia.org/wiki/Lithium_nickel_manganese_cobal...
    • deleted 1y ago
      [deleted]
• jonesjohnson 1y ago
  Proper cooling seems to be the primary thing to do. https://www.sciencedirect.com/science/article/pii/S2590174522001337 https://www.sciencedirect.com/science/article/pii/S259017452... Proper Home Storage systems are pretty safe: https://www.bves.de/en/2024/12/17/study-home-batteries-fire-safety/ https://www.bves.de/en/2024/12/17/study-home-batteries-fire-... There are special containers for transport of (even damaged) lithium batteries, which don't look overly bulky: https://www.zarges.com/en/solutions/transport-and-storage-of-lithium-ion-batteries-also-defective-or-damaged/ https://www.zarges.com/en/solutions/transport-and-storage-of...
• PaulKeeble 1y ago
  Current building regulations in the UK are moving towards outside storage of batteries now because of NMC's having a high tendency to combust. The battery management systems do detect a lot of issues, thermal and shorts but at some point I think government is going to force these to be on the outside of houses. The right answer is LifePO4 for home storage, does not combust and has good enough density.
  • Animats 1y ago
    Agreed. I think that about ten years out, when solid state batteries are widely available, lithium-ion batteries bigger than laptop-sized will be prohibited.
    • PaulKeeble 1y ago
      Once we have solid state cells I really hope the entire industry moves over to them and we just have solid state, LFP and Sodium Ion, all nicely non combustable chemistries that offer different price, power and weight density trade offs.
      • adrian_b 1y ago
        Solid-state batteries will never be suitable for all applications, even if they should suffice for the most frequent of them. Batteries with liquid electrolyte will always be able to provide greater power (i.e. greater current) within certain physical constraints. This should not matter for smartphones or laptops, but it should matter for many things with motors.
        • faeyanpiraat 1y ago
          Whats going on with liquid electrolytes that ensure they "always be able to provide greater power"?
          • ErroneousBosh 1y ago
            It's the common problem with almost anything in physics or chemistry. The Good Stuff has some horrible flaw that makes it incredibly dangerous. When we invented refrigerators first, they used ammonia as a refrigerant which was awesome at moving heat around. It's still used industrially but people die from ammonia leaks. Then they swapped it for freon, which was just about as good at moving heat around, but rotted holes in the ozone layer. So they got replaced with R-134 which wasn't as bad for the ozone layer (but still not great), slightly more toxic, and still quite nasty stuff to handle. At present the best bet for refrigerants turns out to be good old propane, which if anything is a little too good at moving heat around (and your evaporator will freeze if you're not careful), reasonably non-toxic (don't breathe it in, but unlike ammonia a tiny amount in a room won't dissolve your lungs), and its only real downside is that it burns. People are worried about using C3 or C5 (pentane) refrigerant in cars, but the worst that would happen is you'd release about a deodorant can's worth of the stuff into something that's already on fire and contains maybe 70 litres of petrol. Your petrol tank is a bomb, made of a leaky plastic bucket full of explosive. The aircon having a cupful of LPG in it is not your problem in an accident. Thus it is with batteries. It turns out that one of the best kinds of batteries you can make in terms of longevity, power density, and stability is a couple of bits of lead in a bucket of sulphuric acid. They work great. They're in production today, and will probably be forever. Your car has at least one (mine has three, a massive one up front for starting the engine and a couple of smaller ones in the back for running things like the radios and inverter when I'm stopped). However, lead compounds are pretty nasty, sulphuric acid is pretty nasty, they're heavy, they will stop working if you leave them discharged, and in general people would like something smaller, less corrosive, and less dependent on digging up vast areas of China to pull poisonous dust out of the ground. So we have NiCads (oh dear, cadmium, one of the nastiest poisonous metals because it's poisonous all by itself - it doesn't need to be complexed to something organic to get in you), then NiMH (cheaper, non-toxic, and more-or-less a drop-in replacement for NiCads in any given application). Then we've got the various rechargeable lithium batteries which can do exciting things when damaged. But for high power density, low cost, and and high current applications where you don't have to worry about carrying them or tipping them over, you're going to be stuck with lead in a bucket of acid for a while I suspect.
• Animats 1y ago
  Small outbuilding. Concrete pad. Cinderblock walls. Sheet metal roof. Safe distance from anything important. Typical cost is $3000-$4000. Farms often have little buildings like this. (There are pictures of such buildings online. Search is returning awful LLM-generated garbage landing pages, so I don't have a link.)
• killingtime74 1y ago
  Doesn't matter. If you try any of these techniques your insurer will still void your home insurance if your house catches fire.
  • wildzzz 1y ago
    "Hello, State Farm? Yes, I'd like to put in a claim for my home insurance. My homemade electrical bomb exploded and my house- hello? Hello?!"
    • Dylan16807 1y ago
      No, the "doesn't matter" issue is that they'll try to deny you when something else starts a fire.
      • withinboredom 1y ago
        Indeed. It's that "something else"'s fault that the fire started. You should blame them... only in this case: that's yourself.
        • Dylan16807 1y ago
          What? Myself? Are you still talking about the battery starting a fire, and saying that it's my fault rather than the battery's fault? Because that's not an "indeed". I'm talking about non-battery fires. If you're on the same page as me, and talking about non-battery fires... What makes it my fault?? Are you saying any possible fire is my fault? With the implication that insurance shouldn't pay out for any fires ever??
  • rootusrootus 1y ago
    Can you cite a single instance where home insurance claim was refused because the homeowner was stupid?
    • killingtime74 1y ago
• hamdingers 1y ago
  If you have the space for it, just put it outdoors 5' from anything flammable and you're good to go. This is not a hobby for folks in apartments unfortunately. I've had one of my DIY ebike batteries short and fail spectacularly at near full charge and was able to push it with a broom out of the garage into the driveway before any damage was done. Now I have a bench with wheels that I can take into the driveway for initial testing.
  • deleted 1y ago
    [deleted]
  • johanvts 1y ago
    Sounds like it’s also not a hobby for people with neighbors.
    • rob74 1y ago
      At least not neighbors likely to be alarmed when their neighbors run out of their garage at odd hours of the night, pushing a flaming cart and screaming "fire!"...
    • xboxnolifes 1y ago
      Everyone has neighbors. Just depends how close they are.
• oulipo2 1y ago
  Shameless plug: we're building a repairable e-bike battery where you can use your own cells at https://infinite-battery.com https://infinite-battery.com We worked on a very sturdy casing, with some specific features to release pressure and limit the fire event propagating cell to cell, you can check it here https://www.youtube.com/watch?v=v0NXXfCA2CY https://www.youtube.com/watch?v=v0NXXfCA2CY
  • JKCalhoun 1y ago
    Nice.
    • oulipo2 1y ago
      Thanks! Appreciated
  • pcdoodle 1y ago
    That’s pretty cool, but it took me quite a while on my phone to figure out what I need. Been doing e-bikes since 2007. Also, the little plus next to the shop was confusing to somebody that had a beer. I think your product is hot, thanks for making something that the world needs.
    • oulipo2 1y ago
      Thanks for your feedback! Would appreciate any tip you have in making the website more clear, please send us any feedback at contact@gouach.com !
  • typpilol 1y ago
    Are these rated? My local bike shop won't sell anything without that specific safety rating. I forgot the exact number. I've seen that more and more common lately
    • oulipo2 1y ago
      Yes! We have the EU certification and are undergoing the UL certification, it should be complete at the end of the year!
• jeffalyanak 1y ago
  Ideally build it in away from your house, as others have said, but in terms of actual safety systems: -get a high quality BMS from a reputable source, it should supports current limits and thermal probes - configure current limits with as much overhead as possible, the less you drive them, the cooler they'll stay - make sure you have sufficient thermal probes inside key points in the pack(s) and that they're configured in the BMS to cut draw - add thermal fuses as well, knowing where to put these is important, too - house the packs so to minimize fire risk and cascading issues, especially if space is not a concern
• jacquesm 1y ago
  Distance, so a separate building far enough away from anything you want to keep that it won't carry over. Cabling underground but not in a duct. Space the cells a bit and ensure good airflow between them. A single runaway cell is how it usually starts and that in turn usually first shows up as increased internal resistance. Avoid mixing capacities, brands, different internal resistance values, cells that self-discharge, cells that have any sign of physical abuse or damage. (The guy in the video totally misses the internal resistance angle, as well as the self discharge which takes a long time to test and he already spent two months or more on his power bank.) Weld, do not solder your connections. Assemble cell groups first and then do QA on the cell groups as if they are larger capacity cells, and monitor them with a FLIR for any sign of cells misbehaving, especially under larger cell group charge/discharge currents. If a cell in the center is more than a few degrees warmer than those on the outside that's a serious concern. Other prevention measures: strict inbound QA on the cells. That's a lot of work, to the point that if you value your time you are better off buying a factory made pack of a reputable because they will almost certainly do a better job than you will on the safety aspect. Getting Lithium-Ion packs right (especially larger ones) requires more up-front funds in terms of gear (especially testing gear for large volumes of cells is quite pricey) as well. The only reason I would do another (big) pack is if the form factor or capacity I want is not available at all. The brief flash of that 'rechargeable powerbank' in the video has so much wrong with it that it isn't even funny and that's before looking inside the pack. All of those crossing wires, brrr. And those modules in the linked video don't look much better. Oh, and he's got one cell group in there with fewer cells (13:26) so that pack will unbalance immediately during charge or discharge. Effectively the whole pack has as much capacity as that one smaller cell group times the number of cell groups. The lack of integrated balancing wires is another puzzle for me, crossing balancing wires is a major headache when building larger packs, you want the very best grade of wiring for that with vibration resistant insulation and some kind of wire guide to ensure the wires can't move or cross. The whole BMS setup looks like an afterthought, rather than that it was designed in. Oh, no interlock on the two separate breakers for the inverter (configured to work in island mode) and the house power. Wait until someone engages both. You need a transfer switch there, not two separate breakers. His remark that it all looks 'super dodgy' and that 'I do not recommend anybody ever builds a pack like this' is an interesting one: if you are aware of all that, why do such a crap job in the first place? If you are going to go through that much work you might as well do a proper job. Meanwhile, this is really just an ad for JLPCB. Running around the house and the workshop at everything working is a bit cringe, it is as if that's just padding to extend the video runtime.
• superxpro12 1y ago
  If it reaches thermal runaway... there's not much you can do. There's simply too much potential energy in the pack. https://www.reddit.com/r/SweatyPalms/comments/1gbryd1/factory_workers_try_to_extinguish_lithiumion/ https://www.reddit.com/r/SweatyPalms/comments/1gbryd1/factor... Throw it in a massive body of water is about as good as you can do until the energy is depleted. (Also, making a human perform the puncture to initiate a violent chemical reaction is WILD. Do better) https://www.reddit.com/r/interestingasfuck/comments/1nuo0fj/the_safety_measure_used_after_a_large_lithium/ https://www.reddit.com/r/interestingasfuck/comments/1nuo0fj/... For real dev work... essentially special sheds with massive ventilation to handle thermal runaways, rated by amount of kwh.