"Real" Sun Hours [RE-wrenches]

[Chris Daum]

Hi Travis and all:

An smartie engineering buddy of mine came up with this idea for an 
"insolation measuring system".  Here it is from him, verbatim:

Have your customer get a solar module (whatever
wattage he wants), TM-500 w/shunt and a battery.  Wire the solar module so
that it is short circuited through the shunt.  Mount the TM-500's circuit
board to the side of the shunt and run its fused power lead to the battery
positive.  Then connect the battery negative to one side of the shunt
(doesn't matter which side as this is only completing the power circuit for
the TM-500.  What this will do is allow the full short circuit current of
the solar module to flow through the shunt all day long and be recorded by
the TM-500 meter.  No current is flowing to the battery, it is only there 
to
provide power to the TM-500.  The TM-500 only draws 16mA (0.016A) with the
display off or 32mA (0.032A) with the display on so if your customer turns
the display off, he should only need about 140 amp-hours of battery storage
to run this test for 6 months and still only draw the batter down to 50%
DOD.  Actually one of the 98 amp-hour (@ the 100 hour rate) 12V Deka gel
cells would work great and would be cycled down to about 75% DOD over this 
6
month test.  Depending on how often your customer checks the meter reading
(I would suggest weekly since you never know what can happen) all he would
need to do is divide the cumulative amp-hour reading on the TM-500 by the
short circuit current rating of his solar module and that will tell him how
many full sun hours he received since he checked the meter last.  This
TM-500 setup is just a theory in my head so don't try this at home.

What do you folks think of this?   It seems like a dandy way of figuring 
out actual amp hours gained, and full sun hours.

I had a customer in Hawaii where the midday sun was frequently obscured by 
clouds, and he wanted to know just how much power he'd get out of a given 
solar module.  He's tried this set-up and since he's remote (with little 
access to communications), I don't know if it's worked for him--but I'm 
sure he would have dropped me a line if it DIDN'T work.

Chris Daum
Oasis Montana Inc.
406-777-4321 or 4309
406-777-2632  fax
http://www.oasismontana.com


-----Original Message-----
From:	Travis Creswell, Ozark Solar [SMTP:ozsolar at ipa.net]
Sent:	Wednesday, September 26, 2001 11:37 AM
To:	RE-wrenches at topica.com
Subject:	Re: "Real" Sun Hours [RE-wrenches]

HI Windy,

Good point. I am using Sell mode so my charge controller is not doing any
regulation. I feel that this is pretty accurate way to count sun hours for
my site.

If we want to know how many amp hours a solar panel can produce why don't 
we
use solar panels to count amp hours instead using pryronometers or whatever
else than extrapolating from there???

Travis


>
>Regarding using a C-40 AH readout for solar data, it measures charge
>current, so I presume it would be reduced by the unit's charge
>controlling function when batteries are high.
>
>Windy
>
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