[photo-3d] Re: Ni-MH for Viewers

[Mark Shields <beamsplitter@xxxxxxxx>]

I have not used NiMH cells in a viewer, but have used them as well
as NiCd and Ray-O-Vac Renewals in a lot of computer applications.

NiMH are 1.2 volts per cell, same as NiCd. If you don't mind slow
charging, putting them in a NiCD slow charger works fine. It does
take a long time--two days or more--but at that slow rate there
is little danger of damaging them. I leave an AA pair in my
charger for a week at a time, swapping out that set with one that
has been in a palmtop computer (HP 200LX) during the same week.
It works beautifully. NiMH used to self-discharge very rapidly,
but the newer ones are much better. Their capacity has been growing
greatly--the AA ones I use are 1600 mAH.

Memory effect with NiCd occurs when the cells are constantly
discharged only a little bit, and then recharged. If they are
cycled deeply each time, used to or near their rated capacity,
this is unlikely to occur. It is also less of a problem than it
used to be, but can still happen. Some specialized NiCd chargers
actually discharge them first, before starting the charge cycle.

I've not had good results with Renewals except for short-term
standby applications. They don't self-discharge, which is good.
But they have only about half the capacity of ordinary,
non-rechargeable alkalines. Also, while you can get 25-50 charges
if they are discharged lightly (about 10% of rated capacity),
if you discharge them deeply their capacity drops off very rapidly.
This was no good for me using a computer, where it is important
to be able to run the computer a long time, hence deeply
discharging the batteries. Renewals suffer from high internal
resistance, which is worse with the larger sizes. A set of D's
that I got for a computer became essentially useless after two
deep discharges.

So know how you are going to use them and buy accordingly. I do
keep a few sets of Renewals around for standby--great because
they don't self-discharge.

Mark Shields
  |\	   _,,,---,,_** "Whoever welcomes a child in My name ****
  /,`.-'`'    -.  ;-;;,_ welcomes Me," Jesus said, "and not Me **
 |,4-  ) )-,_..;\ (  `'-'but the One who sent Me."  -Mark 9:37 **
'---''(_/--'  `-'\_) **beamsplitter@xxxxxxxx  www.stmattpitt.org*

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