On Fri, 09 Feb 2007 23:09:58 +0000, Ian Malcolm
wrote:

Goofball_star_dot_etal wrote:

I do see where you are coming from, as both myself and Larry made the
obvious but incorrect assumption that a PV panel could be modelled
adequately as a controlled voltage source. It was labelled as an
assumption and an approximation, i.e. a simplification, NOT A FACT.


Yes but it is not an approximation, it was totally wrong and useless
not "useful" at all.


As

it happens, the only effect that correcting that has is to move the
modelled MPP for the better panels above the charging voltage of a Lead
acid battery. This means a small simplification in the topology of the
switching converter. A closed loop converter based on the simplistic
analysis would soon settle within a few percent of the MPP anyway so the
results would be almost identical.


The MPP is light and temperature sensitive. The quoted patent states
that they sample the open circuit volage and apply an offset to arrive
at the (instantaneous MPP)

Leaving out any personal attacks *this* time, Mr Ball,
Their approach is actually questionable *FOR A MARINE APPLICATION* as
they make no provision for extracting power if the panel voltage is
below that of the battery. This frequently happens if the panel is
partially shaded and some cells bypass diodes are conducting. This
wouuld be a not uncommon situation aboard an yacht at anchor, on a
swinging mooring or underway. The panel has to deliver over 140ma at
over 14V before *any* power is transferred. Elsewhere they say it is
stable down to 0.8A and as it seems to be designed for 10A nominal
output, what proportion of the time will it not operate? They seem to be
excessively concerned about keeping the converter in continuous
operation mode, *Probably* to avoid violating a competitor's patent.
It looks like it would be advisable to disable their regulator and run a
float regulator if layed up for the winter as the trickle charging
capabilities are suspect to say the least.


I suspect that the manufacturer the OP was considering were rather
optimistic in their test conditions for a 30% efficiency boost, they
probably tested it normal to the sun, totally clear sky and at 10
degrees C ambient temperatue into a very flat battery. At more normal
insolation levels and temperatures, averaged over a normal battery
charging cycle, the 10% to 15% improvement that most other sources claim
is more plausible. After all, you CANNOT get more out than you can get
at the MPP.

Yes.
http://www.blueskyenergyinc.com/pdf/...PSB2KErevE.pdf page 8
table 2