[APML]: Re: external battery pack

["Stephen F. Gagnon" <gagnon@cebaf.gov>]

>
>Paul Wrote
>>
>>I just purchased a (used) Pentax 6x7 "lockup" body, waist level finder
>>and 105/2.4 lens, all in excellent condition.  I fitted the body with a
>>new battery, but after only about 1 hour in exposure times (about 5
>>10-minute exposures and several shorter ones), the battery condition LED
>>is already dimming.
>>
>>
>>Can someone help explain how to connect an external battery?  I read
>>that there is a way to connect a "cold weather battery pack" but I don't
>>see an electrical connector, and attaching alligator clips to the
>>battery compartment will prevent the body from sitting squarely on a
>>tripod head.
>>
>>Can the external battery be any 6-volt DC supply, or are there specs
>>that I must conform to?
>
>Paul
>
>Pentax makes a remote Battery adapter for a cost of $30. I use this and
>plug it into my Reticle eyepiece output on my mount. I than have my 12volt
>marine battery powering the Shutter works great.
>
>Initially I was worried about the 12 volts but after talking with Tony
>Hallas and Roland Christen they convinced me it was amps that counted not
>volts.
>
>I have some info posted on my Web page under Articles / Format Cameras plus
>a link to Pentax 67 site.
>
>
>
>
>Ian Turner
>email: skyshooter@mindspring.com
>Browse My Web site at: http://www.mindspring.com/~skyshooter/
>

Yikes!

Now, I'm not familiar with the camera in question and I don't know if the
battery is only powering the shutter or if there is some other electronics
it is running, but be *very* careful when dinking around with the input
supply voltage.

Treat the camera as a black box with some internal, fixed resistance. You
can calculate how much current will flow with Ohms law (V = I * R). If you
double the voltage, you double the current which could be very bad for the
camera's inner guts. The amps are what count, but the input voltage will
define the amount of current will flow. Now, there might be a voltage
regulator in the camera that keeps the voltage at some nice level but,
unless you know for certain, I wouldn't try to power a 6V camera from a 12V
supply.

Good luck!


 - Stephen F. Gagnon
   Thomas Jefferson National Accelerator Facility
   gagnon@jlab.org