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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: lithium explosion
Date: Sat, 13 Apr 2024 16:01:13 +1000
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On 13/04/2024 2:52 am, john larkin wrote:
> On Fri, 12 Apr 2024 12:22:00 -0400, bitrex <user@example.net> wrote:
> 
>> On 4/12/2024 10:04 AM, Bill Sloman wrote:
>>> On 12/04/2024 9:16 pm, Carlos E.R. wrote:
>>>> On 2024-04-12 07:19, Bill Sloman wrote:
>>>>> On 9/04/2024 3:03 am, Jeroen Belleman wrote:
>>>>>> On 4/8/24 18:35, John Larkin wrote:
>>>>>>> https://www.bbc.com/news/uk-england-london-68744317
>>>>>>>
>>>>>>> It doesn't look like that one was charging.
>>>>>>>
>>>>>>> Lithium battery fires are a big deal in New York too.
>>>>>>>
>>>>>>> San Fancisco is swarming with illegal, unlicensed electric scooters,
>>>>>>> surfboards, wheelie things, bikes, and motorcycles.
>>>>>>
>>>>>> As the energy density of batteries goes up, failures will
>>>>>> become more spectacular. It's not a good idea to store
>>>>>> both oxidizer and fuel in close proximity in the same
>>>>>> container. It's a recipe for an explosive.
>>>>>
>>>>> Lithium batteries don't explode spontaneously.
>>>>>
>>>>> The "explosion" is actually the last stage in a process that starts
>>>>> when the batteries start self-discharging more rapidly than they
>>>>> should, which warms them up a little.
>>>>>
>>>>> Any properly designed battery management system monitors this
>>>>> self-heating, with temperature sensors at the core of the battery,
>>>>> and on it's surface.
>>>>>
>>>>> If the battery gets hot enough, the higher temperature can lead to a
>>>>> higher discharge rate, and at a battery temperature between 130C and
>>>>> 160C which depends on the battery chemistry, the process can run away
>>>>> leading to something that looks like an explosion.
>>>>>
>>>>> Any properly designed designed battery management system would warn
>>>>> the user when this were incipient and would start discharging the
>>>>> battery if it had a safe place to dissipate the stored energy.
>>>>>
>>>>> It follows that any lithium battery pack that explodes either didn't
>>>>> have a properly designed battery management system, or was being
>>>>> looked after by somebody who ignored the early warnings.
>>>>>
>>>>> All this is too complicated for John Larkin to keep in mind - we've
>>>>> discussed it here often enough that he should know it by now.
>>>>
>>>> Or the battery wasn't attended.
>>>
>>> Warning systems can be designed to be quite attention getting.
>>>
>>>> Battery fires have happened when nobody was near the battery; maybe
>>>> charging.
>>>
>>> A proper battery management system wouldn't let you charge a battery
>>> that had got close to going into thermal runaway
>>>
>>>> Here, several cities have prohibited personal electric things with
>>>> wheels from entering the urban public transport system after a few fires.
>>>
>>> A slightly better informed city administration could adopt a more
>>> sensible rule. Personal electric things with wheels can be designed to
>>> be quite unlikely to catch on fire. One's that aren't shouldn't be on
>>> sale in the first place, and would be prohibited imports in any sensible
>>> region.
>>
>> The US is the kind of place that will instate outright bans on e bikes,
>> vape sticks, and books with gay people in them, but in most states it's
>> perfectly legal to buy crates of fireworks at at time with way more
>> explosive power than that, on the honor system. Kaboom!
>>
>> And fretting about the hazards of exploding batteries with 300 million
>> guns floating around is pretty schizophrenic. Compared to being injured
>> by an exploding bike (or shot by a stranger for that matter) your
>> chances of being shot by a police officer are at least the same, or higher.
> 
> About 1300 people were killed by police in the US last year, out of a
> population of 333 million, about 4 PPM. Cops rarely shoot polite
> law-abiding citizens; don't threaten people, especially cops, with
> guns or knives.
> 
> There were 617 homicides in Chicago last year. I suspect few were
> attacks by strangers.
> 
> NYC alone had 18 lithium battery fire deaths last year, something like
> 2 PPM, and that number seems to be trending up.

If US legislators could understand statistics they'd have introduced 
sensible gun control years ago. Finding a form of words that the US 
Supreme Court wouldn't object to might have been difficult.

-- 
Bill Sloman, Sydney