boB,
I usually put only two in series and use MPPT to down convert to 12
volts. Some RV customers have 6~8 modules, series/parallel. I promote
the use of battery monitors in all systems so if there was a
performance issue, I would have seen or heard of it by now. RV
customers have nothing better to do than to stare at the monitors.
Really though, most RV full-timers are a dedicated group of "off-
gridders" conserving energy and water resources.
Now that you and Dan mention it, I did hear that the polarization
effect did not occur at low string voltages. I have never installed
any high voltage strings with SP.
Larry
On Jul 23, 2009, at 7:56 PM, boB Gudgel wrote:
Larry Crutcher, Starlight Solar wrote:
I meant to type ...NO noticeable loss of power.
Hi Larry.... But how do you ~really~ know you weren't losing power
because of their lower efficiency unless there was
a comparison made ? :) I'm not sure that I believe it's all
that much of a problem, either.
But seriously, I think that what Sunpower ~really~ means is that
they have a problem with their lower efficiency on high voltage
strings.
I don't imagine that an RV installation would be that high of
voltage ?
I would just like Sunpower to explain this all a bit better.
boB
On Jul 23, 2009, at 7:27 PM, Larry Crutcher, Starlight Solar wrote:
I have installed tons of SunPower 90's without any ground
connection on RV's with noticeable loss of power. I believe the
problem only occurs when you have a path to ground from the frame.
Larry
On Jul 23, 2009, at 12:58 PM, boB Gudgel wrote:
Larry Crutcher, Starlight Solar wrote:
Hi Jay,
An interesting quandary indeed.
This is another good example of an application that I was trying
to grill Sunpower about --- as far as grounding their modules
that need to be positive grounded
in order to take advantage of their higher efficiencies. They
couldn't answer this simple question. How would you use one in
an airplanefor instance ?
There are solar powered airplanes (sort of) Is a large faraday
shield enough ? Sort of like the ground radials that Larry has
mentioned. I would
imagine that if you get large enough radials that it ~might~
approach being a virtual ground. Works for antennas though.
I like questions like this one. Sure makes one think a bit.
boB
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