On Fri, 09 Feb 2007 20:52:23 -0500, Larry wrote:

Goofball_star_dot_etal wrote in
:

http://www.jaycar.com.au/images_uploaded/impmatch.pdf



The schematic and chart on page 1 of this pdf is also valid for any DC
circuit, like the inefficient solar panel, where source
resistance/impedance is a good part of the circuit.

It is not
a)A constant voltage source.
b)A linear circuit

"An ideal solar cell may be modelled by a current source in parallel
with a diode"

Even a lead acid
battery has some, mostly insignificant, source resistance, that rises as
it discharges quite rapidly. The point where load resistance equals
source resistance shown on the graph is what I was describing. If you
can operate the solar panel at that point with that load, you get more
power than at any other point.

As to this "measuring voltage" charge controller, I still don't see how
that's possible. ANY load, whatsoever, causes a drastic drop in solar
panel output voltage from its open circuit, natural voltage due to the
large series natural resistance that makes the cells get hot as hell.
They might be able to interrupt the load current, measure the voltage,
then reload the cell during a pulse width. That would work, I suppose.
Cell temperature varies cell resistance an awful lot.

From the linked patent for the device:

"As shown in FIG. 2, an approximation of the open circuit voltage of
array 2 is measured every eight seconds by sample and hold circuit 22
based on a 15 ms signal from oscillator 24. PWM controller 10 reduces
the duty cycle on Q1 transistor to zero for the 15 ms sample period to
obtain the open circuit voltage approximation. During this 15 ms
period the charge on C1 increases to approximately open circuit
voltage and the voltage reading is stored by sample and hold circuit
22. After the 15 ms period, PWM controller 10 returns to normal
operation"



http://www.mrs.org/s_mrs/bin.asp?CID...1&DOC=FILE.PDF
http://www.emcore.com/assets/photovo...SC%20Aiken.pdf

http://quantum.soe.ucsc.edu/research...r%20Thesis.pdf
Look at the graphs and information on pp 23-28 of this thesis paper.

Of course, you will need the powerpoint slides in pdf format:
http://www.ipcrystalclear.info/Share...0workshop%204%
20Nov%202005-%20IMEC/Presentations%20SiNx%20workshop/Carnel.pdf
and
http://www.smn.uio.no/pdf/Wadahl-Seminar/Ulyashin.pdf

Obviously, any discussion on a boat newsgroup is an oversimplification of
a very complex subject...solar cells. We'll need a few million dollars
of government grant funding from NIST to further our education and
experimentation at sea. (www.nist.gov)

See your tax dollars at work. Sign up to get NIST grant and symposium
announcements sent to your post office address. I still get them all 10
years after I signed up. They BEG you to take the money...try it.

Larry