Energy/volume must be good for lithium-ion, as all the more expensive (and
compact) cell phones use lithiom-ion; nickel-metal-hydride is now used in the
cheaper phones, and Ni-Cads have disappeared (maybe due to environmental
problems with disposal).
My experience with Li-Ion in laptops is related to several recent IBM models;
the batteries have always been very unreliable, and need replacing every 12
months or so (or shorter). They do not seem to hold a charge after a relatively
short period. And they are fantastically expensive to replace...
I first met Lithium cells in the backpacking world (sold by MSR years ago). MSR
supplied dummy cells so that one lithim plus a dummy gave about three volts.
Their great benefit was in cold weather; where other batteries died, lithium
seemed unaffected.
I have used a lot of NiCads; most of them end up dying and refusing to take a
charge. In a couple of cases I have destroyed a charger by trying to charge them
(probably due to an internal short in the battery causing a thermal fuse to blow
in the transformer). I still have quite a lot, so obviously some of them work
OK.
Now I use Ni-Mh where possible. They normally have greater capacity than
equivalent Ni-Cads, but for me the greatest benefit is their reliability; I have
never had one fail (despite som overcharging). Note that a charger for Ni-Mh
cells has higher current capacity than an equivalent charger for Ni-Cad, and
should not be used for Ni-Cads. If you use a Ni-Cad charger for Ni-Mh, it may
not get fully charged, even after 24 hours...
mvh / regards
Roger Key
>No, I think the energy/volume density is higher also. The pack I got to
>power my DAT player is of about the same volume as 3 of the 4 AA cells it
>normally takes combined. The three AA NiCad cells would provide only 3.6v
>at 1100 mAh. The Li Ion pack provides 7.2v at 1350 mAh.
>As I said, i think the reason there are no AA rechargeable Li Ion
>batteries is that the cell voltage is 3.6 volts and is dictated by the
>chemistry. Since an AA is nominally supposed to be 1.5v this would be too
>high.
>Giles
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