On Tue, 27 Jan 2009 22:11:33 +0000, Larry wrote in
:

If you look at the cells on a heavily loaded panel, notice how brown they
get overheating in the noonday sun so quickly? That should answer your
above question. ANYTHING you can do, like DISCONNECT (read that series
open circuit regulators) an unneeded solar panel in the hot hot sun to GET
THE CELL TEMPERATURE DOWN is always a GOOD thing. The way to get the heat
down is to LOWER, not raise, the cell current. That part of the cells that
don't have any current going through them never seems to change from that
blue silicon color to that brown, scorched-earth look. It's the CURRENT
that fries them. Shunt regulators simply drive up the cell current, which
drives up the cell HEATING until the cell fails....making the cell salesmen
simply smile. Shunt regulators are for suckers.....
...
All solar chargers on boats seem to suck....about like those boat fans
buzzing away over your bunk....cheap crap. But, I'd never use a shunt
controller as it fries the cells in a hot sun at low latitudes. They all
turn BROWN where the current flows!

I've never seen a solar cell fried in the sun unloaded......even in the
Iranian desert mountains.

Turning brown is caused by UV, weathering and environmental heat, not
heating from load, and has a relatively small effect on power output (on
the order of 5-10%). See:
* http://www.freepatentsonline.com/6114046.html
* http://www.faqs.org/patents/app/20080276983
* http://www.wipo.int/pctdb/en/wo.jsp?...A=WO2005006451
* http://www.patentstorm.us/patents/54...scription.html
More modern cells are more resistant to this kind of discoloration.
Keeping the cell under load isn't an issue.

--
Best regards,
John Navas, publisher of Navas' Sailing & Racing in
the San Francisco Bay Area http://sail.navas.us/