Hi. I have a SmartSolar mppt 100/15 powering a 12v house bank at my garden shed. I also monitor the system with a bmv712.
I currently have 4x 100w panels that on the ABSOLUTE BEST DAYS will output 20.5v each and usually about 5a up to 6.7 but average 4.5a. I once saw 8 amps for just a bit with 3x of the 100w in series but that was a a one time event. They regularly just put out about 4.5~5.6a total. I NEVER run them parallel (don't even have any splitter/joiners)!
We get a LOT of rain and when it's cold in the winter almost no sunlight at all (the panels won't even tirn on the MPPT).
I keep two of the 100w in series plugged in all the time and they put out 39~40v and about 5a give or take on sunny days for a few hours but when needed I add a 3rd into the series to bring the voltage up to 60v.
I would like to add the 4th 100w panel IN SERIES to bring the voltage up to 80v at 4.5~5.6a to run a much longer feed wire from the panels to the MPPT and house bank closer to my house which would be far more convenient than the garden shed where everything currently is at and requires frequent interaction and walking to charge thing daily.
It seems to do fine with the 3x 100w putting out the 60v/ 6a up to 8amp (but super rarely that high, again 99% of the time it is 5.6a or less).
I've used the solar calculator and I always get quoted that I need the FAR more expensive 100/30 at LEAST or even the 150/30 to safely have a 80v/5 to 8 amp setup! But I thought it was 100v and 15a?????
What I want to know is why is my MPPT 100/15 is called a 100v 15a controller if it can suposedly only handle 40v and 8 amps going into my 12 bank? The moment I increase those figures or enter in a series of 4x 100w panels I get quoted the bigger MPPT controllers as necessary despite that at MAX the real world figures are 80v and at MOST ever 8amps and 99% of the time they are actually 90w panels. I could understand running two parallel strings could be iffy but in series, really, that 80v/8a is too much for a 100v/15a controller?
The current house bank is 12v and the max output my system ever does with 3x 100w panels is 240w so far (In 3 years). I don't see how the calculator can be correct in that I need a double-15amps charge controller.
I also considered that it might be 100v max INPUT and 15a MAX conversion OUT which would make more sense in that turning that 80v into my 14.6+v charge in ideal conditions would be maybe a 5.4 multiplier on the amps so my 4.5~5.6a would easily overload a 15a charge controller at x5.4 in an ideal no-conversion losses situation. I have adjusted the figires in the calculator but it still tells me to series 4x 90w panels @ my amps I need at least a 100/30!
So the amps-out on victron charge controllers is all the MPPT's can handle converting amps into then, not the max input? Is that really the case?
