[Noisebridge-discuss] lithium-ion battery questions

Joel Jaeggli joelja at bogus.com
Sun Dec 20 17:30:14 UTC 2009


As you've seen with manufacturers recalls there is a risk associated
with basically any lithium ion battery the fact of the matter is there
are supposed to be safety features associated with any lion battery
stack (notably a thermal cutout) that are there to protect the user.

The common discharge explosion scenario goes something like this. user
suspends laptop in airport but because of some hanging driver the laptop
fails to suspend... It's inserted into a laptop bag with the cpu locked
in a tight loop. 20 minutes latter in a overhead bin it's now 70c on the
outside, having exhausted the battery to the point where the voltage
begins to drop, and having ignored the acpi signal to hault due low
battery becuse it's crashed, the current draw increases as the voltage
drops and the battey goes into thermal runaway... about 10 minutes later
the battery explodes because it's in a confined space and the gas needs
to escape.

John Magolske wrote:
> Thank you everyone for the helpful advice!
> 
> * <michaelshiloh1010 at gmail.com> wrote:
>>>> If no one on this list is an expert, I can forward your question
>>>> to a friend who is quite an expert.
> 
> I believe David's post pretty much pointed me towards why the full
> charge-discharge cycling was recommended, but I would like to get a
> better sense (if that's possible) of the risk involved in using a
> "no-name" replacement battery rather than the official Lenova brand.
> The official battery costs about $70 more, but stories of Li batteries
> emitting flaming gases are somewhat disconcerting.
> 
> * David Yao <kudegra+nb at gmail.com> [091219 21:19]:
>>> A possible reason for his recommendation to cycle the battery like
>>> this is that the OS/BIOS could need to re-calibrate with the new
>>> battery. [...] Doing a full charge-discharge cycle a few times
>>> ought to re-calibrate it.
> 
> I think that's it. Here's a post on the linux-thinkpad list refering
> to recalibration via full charge-discharge cycling:
> http://mailman.linux-thinkpad.org/pipermail/linux-thinkpad/2006-March/032836.html
> 
> From all I've heard, deep draining an Li battery is pretty hard on it,
> so I think I'll just live with an inaccurate "% left" indication for
> now till I can implement a less harsh re-calibration, possibly using
> the Lenovo battery management utilities Gian suggested:
> 
> * Gian Pablo Villamil <gian.pablo at gmail.com> [091219 22:06]:
>> If you are using Windows, the Lenovo battery management utilities
>> are pretty decent, and will prompt you through the calibration
>> process.
> 
> I'm running Debian Linux. But if the calibration is something that
> happens to the battery itself, I'm wondering if I could just get
> out my old hard-drive with Windows on it, boot into that, do the
> calibration, then switch back to the Linux hard drive. Would that
> work? Or am I overlooking something?
> 
> John
> 
> 



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