OT: Kids got an E-scooter?

I doubt that there is any serious quality control on cheap batteries.

Kids are maiming and killing themselves on cheap unlicensed battery-powered scooters and such too.

Imagine maybe a million unused battery-powered toys gathering dust in garages and closets waiting to explode.

A frightening thought! Not so much batteries; more incendiary bombs.

That's why we charged our RC lipos in a fireproof bag...

If it ignites, it would burn through a steel lunchbox.

If you can describe it as a thought. More a deluded fantasy/

Really? Do you have any evidence for that that claim?

This is just more of the usual alarmist nonsense about lithium ion batteries. This should be the kind of forum where we discuss the design of lithium ion battery chargers and lithium ion battery condition monitors - which could, in principle be designed to discharge the battery if the internal temperature of the battery rose high enough to suggest a risk of runaway self-discharge.

Cursitor Doom and John Larkin are much too devoted to their alarmist fantasies to want to think about that (always assuming that they could if they wanted to).

Perhaps you'd like to explain to the lady who's house burned to the ground and her similarly stricken neighbours that this is all just an "alarmist fantasy" Bill.

Alarmist fantasy in action...

Not to be an alarmist, just be aware that even professionally managed lithium batteries can do bad things. Don't keep them in your house...

The claim every e-scooter is going to burn your house down is the alarmist fantasy. The proposition that we should give up on all lithium ion batteries because some manufacturers don't design their products carefully enough is not appropriate to sci.electronics.design.

You don't even claim to be able to design stuff, so this may pass you by. John Larkin does like to claim that he does design stuff, but isn't all that convincing.

"Professionally managed" just means that the people who are supposed to look after the facility are getting paid for it. Getting paid doesn't mean that you are doing it right.

If your lithium batteries are equipped with properly designed temperature monitors and appropriate battery management hardware, they won't burst into flame without generating some kind of alarm well in advance.

The safest option is to put them somewhere where they could burn out, but that is rarely practical.

Tesla power walls are expensive, but a separate outhouse for them would make them even more expensive.

Yeah. A lithium BEV fire has no problem melting the girders of a big parking facility, collapsing same.

But there is also a building Code problem on exhibit. In Baltimore, where row houses are very common, it used to be that the wall between adjacent was just an ordinary wall, so if a fire started in one unit, the whole row would burn to the ground.

So, the Building Code was changed to require a double-thickness masonry (brick usually) wall between units. This almost worked, but the brick wall stopped at the top of the rooms below the attic, which was still in common. So, fires still spread to the whole row, only slightly less quickly.

The Building Code was again updated, now to require that the wall extend a foot or two above the roof (which was sloped flat). Success at last.

Units now burned independently of one another, and the Insurance Companies stopped threatening to exclude most of the housing in Baltimore from house insurance.

I wonder why the UK didn't learn this bit of history. Maybe those units were grandfathered in.

Joe Gwinn

I can walk my whole block on the flat roofs. There is zero gap between houses, and the standard lot is 24 feet wide.

The walls (of new stuff) are fire-resistant drywall, and there is a foot or so vertical extention between roofs like you describe. And we have a lot of firestations and firefighters. There are TWO San Francisco Firefighter Cookbooks.

When I go to Safeway in the morning, there are commonly one or two fire trucks parked ouside and the big macho uniformed firefighters are inside having heated debates about which kind of onions to buy.

Nasty.

there's a crapton of other stuff with possibly dodgy batteries, what makes you think e-scooters so special?

This works with brick as well.

The drywall would need to be pretty thick to be adequate.

I'd guess that the real reason is that bricks were cheap and available in Maryland, but not so much in California, where they use wood for roofs as well.

The style in Maryland is marble and red brick, not wood. In the dense cities, wood is forbidden because it keeps igniting.

Joe Gwinn

Not sure. Just seems like the very worst fires are from *large* concentrations of these cells packed closely together. Perhaps if there's even the slightest heat build-up in a faulty cell there needs to be at least *some* modicum of air-spacing to permit heat release or the whole 'pile' goes into thermal runaway with the devastating results we typically see. I only say this because I've never known individual cells or small clusters of them go *bang* big time.

The problem here is that your reading comprehension isn't great.

The cells may look perfectly normal in visible light, but what you are talking about is thermal runaway.

With lithium batteries, the cells have to get up to between 140 to 160 Celcius before the process can take off. That's hot.

With a charged battery there is always some self-discharge, and that does warm the battery some extent, and it gets worse as the cells get old. The processes that contribute to self-discharge move faster when the cells are warm, so you get more self-discharge in old batteries (but bad charging habits don't help either). They have to be very far gone before they can run away.

Any kind of properly designed battery monitoring system should give you plenty of early warning, and should be able to discharge the battery (if slowly) before they get to be dangerous. It's a design problem, and not one you seem to be able to think about.

Some are incredibly cheap, and I expect that most people park them indoors.

Seems like the problem is that the fuel and oxidizer are stored way too close together.

If only we could separate them—hey, maybe we could save weight and be safer by using air as oxidizer, and even more by not carrying the oxidized fuel around!

What an amazing advance that would be!

Cheers

Phil Hobbs

Don't be silly. That's obviously impossible.