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Comment by devwastaken | Hacker News Reader

Lithiums are nothing to treat carelessly. Friend of mine had a good quality drone battery catch their room on fire. Could not put out the battery, had to scoop it and put it outside until it stopped. The only reason it didn't burn the house down was due to flame retardant materials things are made out of nowadays and they caught it fast enough.

Manufacturing by it's nature has defects, get metal containers for your lithium charging and don't cheap out on batteries. If you have old lithium batteries from laptops, drones, etc, dispose of them at a local transfer station properly. Or at a minimum locate them in something metal that has a lid in an area where open flame would not readily catch something on fire.

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I have the dubious distinction of having burned down three acres of Stanford's Lake Lagunita with a Li Po battery after crashing a drone (this was a soft pack for a DIY drone). We had been meticulous about charging and handling safety, but they still light off like fireworks if punctured. Seven years later, I'm still terrified of these batteries and treat them like explosives.

You could start a fire with an ordinary alkaline battery used in the right way, and these things pack way more energy.

based on your post, not sure if this was a consumer drone battery like a DJI or similar with its own enclosure, battery charging dock/station, or a DIY hobbyist/quadcopter battery such as you might see if you bought a 6s 4000mAH lipo for a 8" FPV quadcopter.

for the latter, the people I know who build and use such things always charge their batteries in an attended environment in some sort of mostly-fireproof setup. one has a small corner of their tech/hobby workbench that has a few 12" ceramic floor tiles stuck to a box like enclosure open on one side.

since lipos are damaged and degrade if held for long times at 4.2V full state of charge, it's recommended for the health of the battery to only charge it almost immediately before you want to use it. ideally you would do that while nearby and paying attention, not leaving it totally unattended.

example would be something like this

https://chinahobbyline.com/shop/detail/RcCar-22.2V(6S)/CNHLg...

the quality of the battery charger also matters. and be absolutely certain you're using the correct goal float voltage setting, charge rate in amps or C rating, etc.

https://www.racedayquads.com/collections/isdt-products/produ...

i have also heard of people who use a surplus steel ammo can (plentiful and cheap in many parts of the USA) for battery charging and lipo storage.

> a DIY hobbyist/quadcopter battery such as you might see if you bought a 6s 4000mAH lipo for a 8" FPV quadcopter.

6S 4000mAhr is getting seriously into "do not fuck around with this" territory. they deserve to be treated like and equivalent weight of gasoline.

My quadcopters these days are mostly small to tiny. (It's been years since I flew anything above the 250g size that changes the rules here.) In the past, I've flown medium/big hexa and octocopters with 7S 5800mAhr batteries (two of them on the big Octo) Those batteries never came in my house. They are stored and charged in a besser block and concrete tile enclosure in my garage which has a direct metal vent pipe to the outside. They get transported in the car in an ammo can half full of sand, never more than two in the one can.

I've only once ever had one of those go off on me - in an ammo can while charging it at the field. Burying it with sand didn't put it out - it just happily burned away and got hot enough to distort the ammo can. I do not ever want that to happen anywhere near anything flammable that I care about.

I still have 4 of those big packs, I use them on an electric bicycle. I kinda hope that if I ever get mown down in traffic while riding it, it'll set fire to the car that nailed me...

I'm much less safety-nazi with my smaller lips batteries though. I store and charge 3 and 4S batteries in the 500 - 2200 mAhr range in my office - in metal tins with small-sh vent holes and watchable lids. I mistreat those batteries somewhat - my fastest quad can draw ~120A at full throttle on a fresh off charge pack (note that you do that for long, it's pretty much vanished straight up in about a second and a half when you do that. It's pretty much impossible to fly that one LOS, without the goggles I'd just lose it instantly.)

> 6S 4000mAhr is getting seriously into "do not fuck around with this" territory. they deserve to be treated like and equivalent weight of gasoline.

I will note that your average laptop has a battery between half that size and matching that size.

serious professional UAS pilots who fly with large collections of batteries specifically choose battery packs that are approximately 99Wh per pack, which fits within common IATA requirements for carry on luggage. on really big UAS such as for cinematic filming purposes these will commonly be connected in series for a 12S string. An interesting loophole which is applied differently, by different airlines, is that you can have multiples of 99 watt hour battery packs individually carried into the cabin, as long as they are discrete units.

another interesting note is that a number of $2000-3000 (USD) gaming laptops are also equipped with 99Wh nominally rated battery packs so that they're still legal to take on an airplane. I was recently shopping for a new gaming laptop and ran into this while evaluating the specs of 11th/12th gen Intel series things from the usual Taiwanese vendors (asus, msi) and their ryzen 5xxx based offerings.

I trust my laptop battery far more than the LiPos I get for my R/C cars, though. Laptop batteries don't seem to go up in flames nearly as often.

Laptop batteries are also discharged at a much lower c rate, and are encapsulated much more robustly than a bunch of lipo cells welded together to make a 6s pouch

> 6S 4000mAhr is getting seriously into "do not fuck around with this" territory.

yes indeed.

I've recently been involved with the design of some fairly large 18650 and 21700 cell based battery packs for designs that closely approach the manufacturer datasheet rated maximum continuous amp draw per cell.

my main message for the people who use these is the following: "any sufficiently advanced battery in serious amount of energy storage, becomes indistinguishable from a bomb or incendiary device, if you look at it from the point of view of watt-hours stored per kilogram of mass"

My desktop machine caught fire one day while I was using it. The graphics board connector started burning. I immediately pulled the plug on it, which put the flames out, and put the machine outside.

When I got the machine repaired, I bought some sheet steel and it now sits on that instead of the wood floor. The case was metal, so I was lucky there. I'll only be buying metal cases for my desktops from now on.

I was very lucky I was in the room when it ignited.

Given the amount modern GPU's are requiring that doesn't seem such a rare occurrence. During some game sessions, my 3080 will max out the capacity of my consumer UPS and ponder if a loose pin on the power connectors could cause a spark enough to jump the connectors. I guess my only saving fate is I let my computer sleep when not in use.

It's not a spark, it's a loose connection. This causes higher resistance, which generates heat, which melts the insulation and then makes it worse. Even though it's only 12V, there's enough amps flowing to cause plenty of issues.

My drone/rc plane loving friend has built a concrete box on a garden outside the house to store all the high density batteries there for this very reason.

This was a huge turn-off for wearables like the the Oura ring. When you do metal work, you take off rings because if a bead of molten metal gets on your very conductive gold ring, you won't be able to get it off, and it's a quick way to get a second-degree burn. Also, "degloving." My fear with these rings is if the battery goes, it's burn time. I can't find enough specs to know if the battery holds enough energy to do this, but my fingers are worth too much to me to take this chance.

Edit: the battery is .0777 Wh. If that burnt up in 10 seconds, that'd be 30 W concentrated on a square cm of skin, then distributed around the ring. I think that's a burn?

It's a burn, but not a very bad one.

that's 300 Joules, a typical .22 long rifle round delivers about 180 J

Cycling on a gym bike for 1 second is also 300 Joules... It all depends how it's delivered!

So IEEE 1584 actually defines the boundary for second degree burns to unprotected skin at > 5.0 J/cm^2 [0]. Assuming the parent comment parameters of 0.0777 Wh discharging thermally over 10 seconds into ~1cm^2 of finger, that is ~27 joules per cm^2 per second for 10 seconds.

I think you would probably lose the finger.

Please correct me if I am wrong.

[0] https://en.wikipedia.org/wiki/Arc_flash#Distance

A few years back I had a Samsung smart watch, and one day I was sitting at my desk and started to feel an uncomfortable burning feeling from it. It managed to give me a little first degree burn on my wrist before I got it off. I rebooted it, and shortly afterwards it did it again, so it's been sitting in a drawer ever since. The only thing close to an explanation I found online was that if it needs to do something intensive like sync 100 SMS messages it can overheat. TBH, though, I think walking around with a cell phone in my front pocket all day is more of a risk.

Likewise we had a battery (don't know if it was a drone battery or for GPS equipment or some other device) burst into flame here at work, charging on someone's desk in their cube. Gouts of evil black smoke rising to the drop-ceiling. We chucked that sucker in a handy bucket and took it outside, now we keep a bucket of sand under the designated charging station desk, just in case.

How would you maintain say 1-3 live, powered on laptops and 6-8 in cold storage (but still used)?

Full metal cabinet preferably away from anything flammable is the simplest solution.

For real? Is there anyone who doesnt just leave their laptop on their desk when not in use?

Just thinking about a typical household these days, say a family of four. That's 4 smartphones, say 3 laptops, probably 1-2 tablets. In my house theres a lot more because every AA, AAA, etc. are lithium ion rechargeable anymore which includes video game console controllers, physical remotes for TVs and other devices, and so on. Also everyone owns a tablet of some sort and a laptop. Not saying these will create a humongous exploiting by themselves but each and everyone is a potential ignition source to start a real fire. You'd have to isolate and protect all of these things, regularly, to really add fire protection to your home.

> every AA, AAA, etc. are lithium ion rechargeable

Are you actually using Li-ion rechargeable AA and AAA cells? Those exist, but because they put out 3.7 volts, are pretty uncommon. Almost all household rechargeable AA and AAAs are nickle metal hydride, which is a much less volatile chemistry (and puts out 1.2 volts, making it mostly drop-in compatible with alkaline cells).

There are plenty of lithium-ion rechargeable AA and AAA cells which put out 1.5v; they have an internal buck regulator that converts the 3.7v to the 1.5v that your device expects.

Interesting, never heard of that. Got any brand recommendations?

Panasonic eneloops?

Those are NiMH.

I've used the Pownergy batteries; I don't know how good they are relative to other brands but they work well enough. They charge over a micro-usb cable.

We have a metal "charging station" in the living room. It's the only place our laptops, tablets, and batteries in general are charged.

Phones are charged in bedrooms overnight though. But I figure this setup is better than having random electronics charging in random places everywhere in the house.

> and 6-8 in cold storage (but still used)

There's a difference in risk between one machine and 6-10+

My devices just sit on a desk lol. I have two laptops working as servers in another room.

But if you wanted to be safer from a potential fire, a metal cabinet is the simplest way to do it.

A deflagration from a lithium battery would just heat it up a bit, maybe start burning other stuff inside, but it's highly unlikely to spread beyond that as it would fizzle out due to lack of fuel (also temperature).

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