nuckolls.bob(at)aeroelect
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 Posted: Sat Sep 19, 2009 6:18 am Post subject: Not aviation related... Electronic though. :) |
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Jeff,
Rick makes a good suggestion. But assuming that a more robust battery
is not available, an external battery pack is an option. An array of
4 ni-cad cells comes across the starting line at about 1.25 volts per
cell so an array of 8 would get you 10 volts. Alkaline cells start out
a bit hotter at 1.5 volts per cell so you only need 7 cells to get 10.5
volts as a starting point.
What the energy rating of your existing battery pak?
The camera will be pretty tolerant of input voltage fed through it's
external power jack. Unless the 'wall wart' power supply is internally
REGULATED, then the 9.6v value is a nominal number and the camera will
probably perform over a range of 8 to 12 volts or something like that.
I used to run external 4-paks of d-alkalines on my Vivitar 283 flash guns.
This gave me enough energy to do a 4-hour shoot without concerns
for battery replacement. Further, the low impedance of the d-cells gave very
fast recycle time on the flash gun, not unlike the recycle time I got
with freshly charged ni-cads. The batty box hung off my belt and plugged
into the flash-gun's external power jack through a coil-cord.
For your application, you might consider an 8-pak of C-nicads like
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SY123T-ND
These offer 3,000 mAh of capacity. If you want more, there are some
D-cells (harder to find) that will go up to 4,000 or more.
These have solder tabs and will assemble into a pack that is MUCH
more reliably connected than the spring-loaded battery boxes for
individual cells. You could bring a lead-wire out at the center-tap.
To charge this pack, a simple 120 vac line cord that feeds a series
connection of 1N4007 diode and 7-15W light bulb will emulate a 40-100 mA
constant current charter that takes awhile to recharge the cells but
won't seriously over-charge them.
Is this a portable application or running in a vehicle? You could
craft a 9.6 v REGULATED adapter to run the camera from a vehicle's
electrical system.
Alternatively, you can go with a 7-pak of D-alkaline cells and
throw them away when used up. This will offer MORE capacity than
a rechargeable pak of the same size, somewhat less expensive to
build. But after you've gone thorough 10-15 sets of alkaline cells,
you've expended the cash for one set of ni-cads. Of course, you don't have
the hassles of waiting for a ni-cad pack to recharge either. Your
ultimate choice needs to fit design goals.
Bob . . .
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( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
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