Date:         Wed, 27 Sep 1995 16:39:14 -0500 (CDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         dakhlia@wuecona.wustl.edu (Sami Dakhlia)
Subject:      Charge control 1 (long)

A couple of months ago, I reported having a problem with my bus-mounted
solar panels: the 15 Amp fuse between the array and the battery kept
blowing. Bob Hoover and Cetin Seren offered help and patiently explained
some rudiments of electro-physics. In the end, they diagnosed the problem:
me. 

Yes, this is embarassing to say the least, for *I* was the moron who kept
blowing the fuses with every attempt to measure the panels' output on the
closed circuit. Of course I ended up measuring the battery's cold cranking
amps. Duh. 
 
However, Bob and Cetin also recommended some additional measures. Cetin
suggested, among other things, adding a diode to the circuit to prevent
the battery from discharging through the panels overnight. Bob, in turn,
suggested that a charge controller between the panels and the battery
would prevent it from being overcharged and from boiling dry. I listened
to both gentlemen and finally found the time to implement the changes a
couple of weeks ago. Things are working fine now. 

It turned out that Bob had previously published an article on how to
manufacture such a device for a few bucks worth of electronic components
plus the price of a quality relay. The article, one in a series called
"The Portable Pakratt (tm) -- Emergency Power," appeared in the May of '87
issue of CTM Magazine, pages 25 through 30. Bob kindly sent me a copy, but
must have quickly inferred from my writing that I am not the most
competent guy with a solder iron, for he graciously sent me the finished
product just a week later. 

The circuit had been hiding in a drawer for some years and he wasn't sure
if it was still functional. All I had to do was to put it in a box, attach
an LED (so you know when it's kicking in), tweak the pots, wire it up twixt
the battery and the solar array, and then test it. 

Of course, this gizmo finds more applications than just solar charging.
Your power source could be a diesel powered generator or converted shore
power, for example. It could be useful to all you campers with dual
battery setups by replacing the primitive 120-minute timer that some of us
have. 

The next post contains a digest of questions and answers on the controller.

-- 
Sami ('75 Westf.)
dakhlia@wuecona.wustl.edu
http://wuecon.wustl.edu/~samid/