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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: OT: Kids got an E-scooter?
Date: Tue, 25 Jun 2024 21:11:24 +1000
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On 25/06/2024 12:48 am, john larkin wrote:
> On Sun, 23 Jun 2024 12:51:30 -0700, wmartin <wwm@wwmartin.net> wrote:
> 
>> On 6/23/24 09:56, Cursitor Doom wrote:
>>> On Sun, 23 Jun 2024 11:25:21 +1000, Bill Sloman wrote:
>>>
>>>> On 23/06/2024 9:58 am, john larkin wrote:
>>>>> On Sat, 22 Jun 2024 22:39:48 +0100, TTman <kraken.sankey@gmail.com>
>>>>> wrote
>>>>>> On 22/06/2024 18:22, Cursitor Doom wrote:
>>>>>>> On Sat, 22 Jun 2024 09:12:04 -0700, john larkin wrote:
>>>>>>>> On Sat, 22 Jun 2024 13:22:25 +0100, Cursitor Doom
>>>>>>>> <cd@notformail.com>
>>>>>>>> wrote:

<snip>

>  From what I've read, most lithium battery explosions happen when the
> batteries are idle, neither charging nor discharging, basically
> connected to nothing.

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

> The times from normal to smoking to exploded is
> seconds.

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.

-- 
Bill Sloman, Sydney


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