BZZT. OK, that's it. You've already received enough Brownie points for
volunteering information about competitive products, so you can just
cut it out now. ;-)
OK... I was told (by one of my betters) that for every couple bad
things to say, I had to say something nice too... It's hard
sometimes.
Bob (Reimiller) is correct about their algorithm not being optimum.
The constant voltage offset from Voc doesn't take into account partial
shading of panels and aging etc....
In one of my MX60 test installs here at the factory, I have 2 strings
of 3 Sharp 185 panels in parallel. Every morning there is partial
shading (it's a great example of this very common real-life problem.)
When nothing is shaded, the MPP is about 75% of Voc (about 90 volts),
(not constant offset, but constant percentage of Voc which is about
the same thing), but when partial shading occurs, that MPP voltage
drops to about 68 volts. It works its way back to about 75% Voc
during the course of the morning.
Last summer, when I got about 10 Amps out, (24 Volt battery), at 90V
MPP, the MX60 would find the MPP at 68 Volts and I was getting about
13 Amps out. Significant increase in my book. This is one area where
that other method, patented or not, just doesn't cut it.
BTW, the constant ~percentage~ of Voc method was documented in a paper
in 1982 and has been used by AERL (and other MPPTs) since. It's
essentially the same thing as constant offset from Voc but still
doesn't take into account the partial shading (etc...) issues.
Also, the MX60 has a mode (U-Pick) where you can run the MPP at a
percentage of Voc and samples it at a user picked interval, if you
want to.
And midi ?? It's all so much fun don't you think ? I spend quite a
bit of time (not nearly enough) in my little basement studio..
OK, Now, back to our regularly scheduled Christmas !
boB (Yes, that's "Bob" spelled backwards to avoid confusion)
Interesting that you actually considered the MIDI interface
specifically.
And all de best in '04. Thanks sincerely for your time and interest.
-=s
That aside, I wonder if Mr. Reimiller can point out another controller
with inputs for an external shunt. My C-40 certainly has nothing of
the kind.
I lookd at the Solar Boost 3048 (I need a charge controller to handle
25 amps at 24V) and it has an input for external shunt. It can use
that input to switch between absorption and float based on battery
current. I don't know if this feature is unique to this model or not.
I've rejected the 3048 because of it's questionable (from an
engineering philosophy standpoint) way it determines
the power point. It is a fairly brain dead method of open circuiting
the solar array every 10 seconds to measure the voltage, and then
setting the desired array voltage when loaded at a fixed voltage
less than open circuit. That's too bad, because one of the things
I liked about it was that the remote panel output was simple analog
that I could feed into my house/barn internal network without having
to reverse engineer someone's protocols.
As much as I like my Trimetric meter, for example, it doesn't talk to
my C-40.
That's been one of my pet peeves about this type of equipment as well,
poor integration.
I'm tempted to quote earlier posts musing about the potential benefit
of an open standard for control and data interchange between power
devices, using MIDI as an example of an interface that permitted an
explosion of new applications in electronic music. But I won't.
It's sort of the same situation as you have with communication between
home entertainment equipment, each manufacturer has it's own
protocols.
I remember building a circuit using one of those 8 pin PIC processors
that would receive the remote control signals from my JVC receiver and
translate them into the codes required by my Pioneer CD changer.
Bob
