Ian Malcolm wrote:
....

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 couldn't find anything on the Blue Sky or Outback sites that address
the issue of raising the voltage from a partially shaded panel so the
it is at the charging point for the battery. In theory, there's
nothing to prevent this. But the situation is complicated because
many installations have several panels in parallel (I have three) the
shading would not be even.


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.

The literature specifically says "up to 30%" gain; they certainly
don't claim that will always be possible. In particular, it depends a
lot on the temperature, since panels will put out a much higher
voltage when cold. Thus, the gains would be less in the tropics, more
in temperate zones in colder seasons. Also, gains are more with a
depleted battery, less as the battery is charged. The web sites are
pretty up front about these issues, admitting that gains might be only
10% in some scenarios. As I've said, the system I checked out had a
25% gain, which the owner said was typical.