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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: lithium explosion
Date: Fri, 12 Apr 2024 15:19:34 +1000
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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.

John Larkin doesn't seem to read data-sheets all that carefully, and he 
doesn't expect the manufacturers of "electric scooters,surfboards, 
wheelie things, bikes, and motorcycles" to be any more careful.

Jeroen Belleman is effectively saying that they should be, but hasn't 
spelled out the advantage of using more careful design to cope with the 
known dangers of using lithium batteries.

-- 
Bill Sloman, Sydney