I have 2 pairs of 120W Evergreen brand panels. Each pair has individual 50' round trip #10 wire. I have Blue Sky 50A (output rating) MPPT controller. The controller accepts 12V or 24V (nominal, actual voltave is ~ 17/34V) and can be either 12V or 24Voutput. Change is done with dip switches. Originally I had the panels in series which gives 32A in good sun with high battery voltages and up to 38A with lower battery voltages, like when I run the microwave. I noticed that at low light levels, (current below ~2A @ 24V input) the unit goes to bypass, effectively losing half the power. I think below this current level, the controller operations are not efficient, so they are shut down. Seeing this, I rewired for 12V input by placing the panels in parallel and changing the dip switch. This helped with the low end current, but the max output dropped to 24A. I decided I get more overall power from the series config and assume the cause is less wire loss. Any shading in series config effectively removes the 2 panels in that circuit. I am planning a long passage, Grenada to Ithaca, NY and sails shading the panels is a big issue. I will probably wire for 12V input for the trip. Shading is a big problem, set a baseball cap on a big solar panel and it mostly stops. Keep in mind: Maximum current is roughly 4 hours a day, possibly half current for 4 more hours. 480 Watts of panels supplies my ~150A/H per day needs and in the spring I have excess that I use to heat hot water using the 120V inverter. I can get behind if there is a long overcast period, but catch up while using the engines for moving. Lee Haefele Leopard 38 Cat, Alesto 2
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