: Can anyone enlighten the 'Mr. Joe Soap' PDA users about the battery
: options generally available?
: I, personally, would like to hear from the HP/USR/Casio/Apple
: technical people, whom should know about such things.
I can speak about battery technologies in general for flight
conditions, that may answer many of your questions.
: So, what is the best option...
: NiCads - Low Voltage and dodgey performance but cheap,
These tend to be 1.2V/cell, but they stay within a tenth of a volt
of that until they are discharged. When they drop though, it's damn fast.
In fact their discharge curve looks like the frequency response of a really
good low pass filter. One must charge and discharge them along the flat
portion of this curve to maximize charging cycles.
One more thing about NiCads, they can dump current in a way no other
small battery can. I've seen a pack of 4 AAs pump 40 AMPs continuous for almost
an entire minute ( the leads off of the pack did catch fire). There are some
with a larger maH rating that can not pump current as well.
: Lithium - Over priced and poor price/performance.
: Lithium Manganese ?
: Lithium Iron Disulphide ?
: Lithium Thionyl Cloride ?
: Lithium Copper Oxide ?
Long shelf life primary cells. Having seen these little suckers
blow up, I would not use them in a device that was not rated for them. Sure
the chances are slim to none, but I don't like the idea of them sitting on
: Lithium rechargables = High street avilability in AA size?
Lithium Ion technology. Very expensive last I checked, but they
provide a high energy density. This may be the next battery technology I
check out for my ham rigs and palmtops.
: Alkaline, - relativley cheap and good price/performance
Primary cells, with one of the higher energy densities of none
* batteries (On this list only the Lithiums are better). They have
a horrible discharge curve though. It's constantly decreasing in voltage,
with the slope being determined by the current. A variable switcher is
required to get a constant voltage out of them.
One advantage of newer alkalines is that they actually regain
small proportions of their lives back if left to sit in a partially
discharged state. The amount is small, but an occasional user will notice
a longer period of use as compared to the secondary cells that tend to
discharge themselves(NiCads can mostly discharge over a two week period
for certain designs, and battery age).
: NiMH - the rechargable 'great unknowns'.
Not really. I've been using NiMH for a few years now. These things
are great replacements for low to medium current applications of NiCads. They
tend to offer 25-30% more energy then a similar NiCad, and have similar
discharge curves. The one thing to watch out for is that NiCad quick chargers
may have problems telling when to shut off for NiMH due to a different delta
V at the end of the cycle.