Stuart Allen <allen@SONY.DE> asked,


>2) As this is a low discharges application, is NiCad or NiMH the most suitable,
 or something else?

NiCad batteries self-discharge fairly quickly.  They lose a significant
portion of their power in just a month or two, even without any load.
NiMH batteries are even worse than NiCads when it comes to
self-discharge.

Alkalines might be a better choice here, as they self-discharge very
slowly and have at least twice the total power of a similar sized NiCad.
You might want to look into the "Renewal" rechargeable alkaline
batteries.  These also have very low self discharge rates and should
last a long time between charges.  However, they will have to be removed
from the device and charged externally in one of the special Ray-O-Vac
Renewal chargers.

Lithium Ion batteries are probably way too complex.  I opened up a dead
Lithium-Ion pack that came with a Sony camcorder and it has a PC board
inside of it!

If you can accept non-rechargeable batteries, straight lithium is
probably the way to go.  A lithium D-cell typically has 6 or 7 AMP hours
of capacity at 3 volts!  Their shelf life is very good too.  But be
prepared to pay a high price for them.

Dave Mullenix