Phew, my feet ache after trapesing up and down the eastern half of the Slough Arm today looking for woody growth (see my previous post) in the edges. We didn’t find a lot but sent in about a dozen or fifteen reports, mostly of saplings. The most surprising thing we saw was a boat actually moving down the arm, so rare that we almost sent in a report of that!
Now then, solar. Well I ordered a shiny new 120w monocrystalline panel from Midsummer Energy. I chose that one because it is narrow and ought not to interfere with centre ropes on the roof of the boat. I had adapted my new stands (more of which another time) to the specific width of the new panel and was just about to drill the fixing holes in the panel frame when I thought I should just check the specification label on the back of the panel. My heart sank. What was this? The open circuit and max power voltages were at least two volts higher than the spec on Midsummer’s web site. Was all my research and thinking in vain? Would this mean if I connected up in parallel to my old 95w panel that the new one would be dragged down below its proper performance? “Woe is me” I might have said, except I said something rather less printable.
To cut a long story short, after a dialogue with the tecchies at Midsummer it’s OK. As I had explained in previous posts, they confirmed that series connection was a No No in my case but when in parallel, the MPPT controller will hold the voltages from the two panels at an appropriate level and they’ll perform as well as expected 99% of the time. That other percent is that rare occasion when the sun is out in the perfect position and everything is at max power, then my 120w won’t quite make all it could, but still comfortably over 90% of what it could. The rest of the time on normal or dull days the panels will perform just as they should, which in this case is better than most panels because this particular new panel which uses American Sunpower cells is better than others in lower light levels. That suits me fine, I’ll get better than I might expect 99% of the time and a tiny bit less 1% of the time. Midsummer explained that mine is the first of a new batch they have just received and they hadn’t noticed the voltage increase. Their website has now been amended accordingly and they’re sending me some much needed free cable and plugs as a recompense for my distress.
I think what I had overlooked is that the MPPT controller would manage the slightly mismatched voltages and make the best of it.
PS My blockbuster novel Jobs for the Boys is free again this week (Tue-_Sat) on Kindle Cheap at half the price. After that I’m hoping to reset it at 99p since a neighbour tells me that she always looks for the 99p books on Kindle. Maybe that’s where I’ve been going wrong, £1.15 was too up market. My cut will go down to 28p, but a million times 28p is OK by me. I can’t wait to get rich.