The AA type battery needs about 120 to 150 ma of current minimum to properly
charge. This would be the threshold charge current for the battery. To
maintain the charge, about 15 to 30 ma of charge current should be adequate.
This is for the average. The exact specs should be enquired about from the
manufacture of the battery you want to deal with, if you want to have peak
efficiency.

NiCads are best stored in the discharged mode at about 60 F, to 70 F deg.
When new, NiCads store best if never charged. It is the opposite for lead
acid type batteries, including lead acid gel cells when it comes to storage.
Lead acid batteries have the best shelf life if kept properly charged up.

Concerning any of these batteries, they will usually not last more than
about 3 years whether they are used or not used. The chemical makeup inside
these batteries breaks down with age. Most of these batteries are good for
about 600 to 1000 charge cycles over their lifespan. After about 350 to 400
charge cycles, they start to very slowly go down from their peak performance
after each charge, regardless of their age. This is for most chargeable
NiCad batteries.

The above in relation to NiCads, can also apply to most Lithium based
batteries as well. One exception is that Lithium based batteries charge best
if pulse charged, rather than pure DC charged. DC charging Lithium cells
lessens their average lifespan in relation to what their best lifespan would
be.

--

Jerry G.
======


"Brad" wrote in message
...
Hi,

NMH batteries have a poor shelf life after charging them. I
would like to build a "trickle" charger to keep them (1.5V AA) charged
until I need them. They will always be in the charger. I thought about an
8
cell holder. Cells will not be charged in series. Each cell will have a
resistor in series with it. What is a safe trickle current (always present)
for a AA NMH battery?

Thanks in advance, Brad

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