Charging a dead battery

Archived from groups: comp.sys.laptops (More info?)

In article <40BD14F5.E933D562@nospa.com>, ms <msa@nospa.com> wrote:
>I just got a used TI/Acer 900T laptop loaded with W95. Windows runs, but
>I noticed after shudown that the lithium battery needed charging. It is
>still charging in the computer 5 days later.
>
>There is a spare battery that is probably totally discharged. My plan is
>after the installed battery is recharged, to replace it with the dead
>spare battery and charge that battery in the computer.

The chemicals used to manufacture lithium ion batteries have a shelf
life of about 3 years, whether actually used or not. Storing them fully
discharged will reduce the capacity further. It is unlikely that the dead
spare will give you any useful service.

Archived from groups: comp.sys.laptops (More info?)

ms wrote:
> I just got a used TI/Acer 900T laptop loaded with W95. Windows runs, but
> I noticed after shudown that the lithium battery needed charging. It is
> still charging in the computer 5 days later.
>
> There is a spare battery that is probably totally discharged. My plan is
> after the installed battery is recharged, to replace it with the dead
> spare battery and charge that battery in the computer.
>
> If I never boot up during the charge cycle, what will happen to W95,
> when the CPU sees the dead battery as it gradually charges?
>
> Advice?
>
> Mike

A properly designed lithium battery charger will refuse to initiate
charging on a battery that's below some threshold...maybe 2V/cell.
It _may_ trickle charge for an extended period until the battery reaches
the threshold (at that low current the cells may NEVER reach the
threshold)...or it may not...or the computer in the battery may
permanently disconnect the battery if it goes below the threshold.
Depends on the design. in all liklihood, the battery is toast.

You may be able, but probably not, to perform the DANGEROUS operation of
charging the battery externally. You may be able to perform the even
more dangerous operation of opening the pack and charging each cell
independently. If you're very lucky, the battery computer will reset
itself. I've got several brands here that I've not been able to figure
out how to reset even with good cells properly charged have been
installed. It's probably trivial, but it seems to be a closely guarded
secret. If you find any technical details, please publish 'em.

Safest thing is to borrow a good battery to insure that the charging
circuit is working then buy yourself a new battery.
mike

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