If you overcharge the cells and do not have proper pack protection they can
fail rather spectacularly. At the Microchip Masters conference one of the
engineers mentioned they had a pack explode rather violently when they
intentionally defeated the protection circuits and overcharged a pack in a
test.
I have designed a charger for a client of mine and the tolerances are tight
to get the maximum energy out while not reducing the cycle life. All the
cells are in packs with protection circuits built in.


At 12:17 AM 2/2/99 PST, you wrote:
>    You know the charge voltage has to be set to 1% tolerance, right?
>
>I have heard that (actually, I think I heard 0.5%)  At the moment I'm
>mostly looking at chip sets.
>
>I fully believe that for maximum charge in minimum time, and for maximum
>cell lifetime, you have to follow some very stringent charging regimes.  I'm
>not sure what you can get away with if you're willing to settle for a
>partial charge overnight (already, someone here has claimed that you can
>charge them at C/10 indefinately) or reduced cell lifetime.  In any case,
>I'm being quite careful.  It seems quite unlikely that a 10-50mA charge
>current would cause a 4/3A cell to explode or even burst into flames - you'd
>have to have some an internal catastrophy to get "access" to the cell
>charge, since 200 mW or so won't even heat that size of a package
>appreciably...
>
>BillW
>
>
Larry G. Nelson Sr.
mailto:L.Nelson@ieee.org
http://www.ultranet.com/~nr