ivorandrews avatar image
ivorandrews asked

Solar panel configuration with bluesolar mppt 150/ 85

Hi everybody

I'm in the process of putting together my first solar system. I have a victron quattro 48 10000 along with bluesolar mppt 150/85. I also have the bmv-700 and the colour control.

I have a bank of 8 12 volt 180ah AGM batteries wired as two parallel banks of 4 in series, giving a resultant 48 volt 360ah. I also have a generator set on board which currently provides mains power when the batteries become discharged.

I have purchased 9x panasonic hit 245w solar panels. These operate at a maximum of 44.3 volts. I can either use eight panels wired as series pairs. Or I can run the full 9 panels with 3 paralleled banks of 3 series wired panels.

My resultant voltages would be 132.9v with the 9 panels or 88.6v with 8. I have read in the manual for the blue solar mppt that the PV voltage must not exceed 150 volts under any circumstances and that is in the coldest of conditions. Further to this in the cable selection chart it is said that maximum efficiency is it twice the battery bank voltage.

I am therefore trying to weigh up the advantages and disadvantages of running a 9 panel system or an 8 panel system as with 9 panels I'm approaching the maximum voltage but gain an extra 245w of power.

I would really appreciate the opinion of somebody more experienced than myself in setting up such a system.

Kind regards, Ivor

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klim8skeptic avatar image klim8skeptic ♦ commented ·

The 72 cell hit's seem to have a voc of 53v. String's of 3 panels not recommend.

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JohnC answered ·

Hi Ivor. I've a similar system, but older 9x 195W panels wired 3S3P. A little lower V (can't find them right now), maybe 2-3Voc lower than yours. And I'd like to show you this - not specially selected, just today's:

Very poor solar day, with a lot of cloud & intermittent sun. Unpleasantly cool, but not freezing. Note the low panel V at the start and end of the day, and if I were to have only 2x panels in a string I'd be possibly working below what my 48V bank can accept. There's a little more to it of course with mpp tracking influencing V's (note early V before production starts), but this is what you're likely to see.

Your CCGX can be setup to provide the same info, and in your situation, I'd go 3x strings and see what happens. Even if you try it out first with a single string on the back lawn.. :)

The upside of the longer strings is that you'll see more energy to your batts over the day.

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