Re: NiCds in viewer

[P3D Dr. George A. Themelis <fj834@xxxxxxxxxxxxxxxxxxxxx>]

>>Steve mentions he uses NiCds in his viewer. This is perhaps folly if 
>>one  does not find a suitable bulb to match as the two D cells 
>>give only 2.4  volts instead of 3 volts as would normal batteries. 

>Dr. T sells 2.5V bulbs. They work beautifully with the 2.4V coming out of
>two nicads.

BobH, FYI, most two-cell blubs are rated for 2.5 V... "Normal" batteries
give less than 3V under load and the voltage drops with time. NiCds show
less volage drop under load and stay within tighter limits between charge
cycles.  The "best" choice depends on how the viewer is being used.

I use NiCds and I like them... For a "heavy user" they have many advantages...

In my first edition Realist red-button viewer book (now out of print) I
have a graph that compares the NiCds and alkalines used in a red button
viewer with the halogen 2.5V/0.8A bulb.  The intial voltage (under load) of
the Alaklines is 2.8V vs. 2.5V for the NiCds.  The NiCds oscillate between
2.5 and 2.2 V needing recharging every 2 hours (under constant use).  The
voltage of the alaklines drops slowly... In only two hours it is down to
2.2 V (same as the lowest the NiCds will ever get.  In 4 hours it is 2.1 V
and it ten hours it is a misearable 1.8V.

For a bulb that draws a lot of current and for heavy use, the NiCds offer
better performance.  But, if the viewer is used infrequently, the low-
maintenance alkalines are preferred.

George Themelis


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