How safe is this disconnect/discharge/recharge/reconnect operation? I'd
rather spend the money than risk well...me. Also, I haven't opened this
packs up, but what if there is only one cell? Is it possible for the
cell to simply die?

Thanks,

Josh
joshy@mb.sympatico.ca

Alan Beeber wrote:
>
> Lithium Ion battery packs are not for the faint of heart. Sony and Apple lost
> facilities to fires caused by Li-ion failures, and the company I used to work
> for had several small fires, contained by elaborate engineering controls.
>
> The protection circuit usually consists of a voltage comparator chip and one
> or two FETs used to interrupt the battery current during overcharge and
> underdischarge conditions. The voltage comparator senses each cell in the
> battery stack separately. You have to disconnect the cells and
> charge/discharge the cell that is out of balance before you can reconnect the
> circuit. Permanently disconnecting the circuit is asking for trouble.
>
> Barry Gershenfeld wrote:
>
> > Li-ion has this really neat runaway failure mode which can make
> > them catch fire or explode.  Thus they are very careful about
> > their treatment and no one will sell packs without that circuit.
> >
> > The circuit will disconnect from the battery if it is overcharged. It
> > will also disconnect if overly discharged; this also protects
> > the battery.  Despite all this if you charge a discharged pack or
> > put a load on the overcharged pack the battery should reconnect.
> > I played with one of these myself on a lab power supply.
> >
> > Of course yours might really be broken in which case I don't
> > know.  But check the circuitry for a fuse.
> >
> > Barry
> >
> > >Does anyone know why lithium ion battery packs fail so easily? I've had
> > >two die on me in under a month, two separate types of devices too. I've
> > >been told that it's not the cells, but the little circuit in the pack
> > >that dies, which renders the pack useless. Anyone have any idea why this
> > >happens, what causes it, and why they aren't a bit more robust? Also a
> > >general question, should I be keeping the battery packs charged when not
> > >in use (i.e. does allowing them to self discharge over a period of
> > >months adversely effect their life)?
> > >
> > >Thanks for any help,
> > >
> > >Josh
> > >joshy@mb.sympatico.ca
> >
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