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Old 27-02-2012, 16:19   #31

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Re: Solar Experiences

I think one of the ghosts that will haunt MPPT for a while is the measurement of input and output. If it was pure DC, or regular sine wave AC, the measurement would be fairly straightforward and reliable. But the output is pulsed DC, with apparently pulse height, width, and frequency all being variable. So a "simple" DC power reading won't be accurate. And even an RMS-reading meter won't be accurate because it isn't a simple AC or simple pulsed DC waveform either.

Then to add icing to the cake...apparently the output from the solar panels, which normally would be simple DC, is NOT simple DC any longer because the MPPT panel is varying the load on the panels, which is moving the powerpoint and changing the output voltage from the panels on a frequent basis. How frequent and how much in what ways...that's another "Sorry, confidential" proprietary bit.

So we can measure what's happening, but simple meters, and I suspect the "simple" power management systems and the "simple" displays on the MPPT controllers themselves, are all telling something close to the truth--but we can't be sure of how close, either.

There's no question they WORK, and little question of about how much they may be doing, but until the chipsets of secrets become more standardized...Ah, who really wants to see the sausage being made anyhow? <G>

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Old 27-02-2012, 19:19   #32
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Re: Solar Experiences

Simple enough, put an ammeter in series with an MPPT output lead.
Heck, even an analog if it's halfway accurate, and you could move it to the input side to compare.
I suspect the digital meters will average a pulsed reading.

My golf cart batteries were a lot happier after I installed the BlueSky.
I now have LiFePo4's but that's another story.
See the thread on Lifepo4's for a house bank.

Memento,homo, quia pulvis es, et in pulverem reverteris.
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