A few weeks ago I set up my 3 panels outside and was getting 300~ watts as expected (on sunny days). But today I noticed I’m only getting 30~50 watts on a sunny day. I plugged each one in individually and all 3 seem to work, but only produce 21.7 V (and zero watts because of the 35V requirement). I made sure they were clean and everything. I’m just not sure what’s going wrong all of a sudden. One odd thing I noticed is I’m only getting .6 amps.
All your mc4 connections between the panels(connected in series) were nice and tight as well?? If they all worked individually/separate into the unit, they totally should be pulling more wattage then that given the sun and conditions were the same. With the amps showing up soo low, def tells me you got a weak “link in your chain”.
I’d go back, make sure your connections are nice and secure, and try using 2 panels in series 1st… and then add the 3rd panel. Those mc4 connections can be finicky so hopefully it was just a loose connection initially.
And just for safe measure, make sure your set to PV rather then car on your input options. Let us know your findings.
Sorry for the late reply, we had a series of rainy days, the rainy season just ended here in Japan haha.
So, I’m now running a solid 280ish watts, but the only thing I did is move the entire support structure for the 3 panels further out into the yard. The panel nearest to the house was half in shadow. My thinking was, well I won’t get full output out of that panel, but I should still get around 200W. Before moving the panels I was only getting about 40W, then moved the rack further out in the yard and got 280. Is there some limiting factor that the weakest panel determines the output? Or maybe the last in the chain?
Thanks!
Ben
In series, any shade on any of the panels will dramatically reduce the power of the system. That’s the drawback to solar panels in series. It is one long “single string” where the weakest panel is your limit. If you were getting 30-50 watts from the three panels in series, it means the shaded panel was only producing 10 to 17 watts which limits the other two panels to, 10 to 17 watts.
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that’s really fascinating. I admit I’m new to this stuff - so the least powerful panel in the series determines the output. wow. So, are there other ways to align your panels to avoid this? Again I apologize I’m very new to this.
In your scenario, since the AC200 requires at least 35V to charge, you’re sort of stuck using all three 120W panels in series. If minimum voltage wasn’t an issue, you could put all three panels in parallel which reduces the effect of a shaded panel.
Understood. Thanks for the information, it was very helpful :
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@Kinpatsu hey man check out this video sometime when you get a chance. He’s got a bunch on YouTube that REALLY gave me a better understanding on the importance of how solar is wired up, but this one will give you a solid overview for sure! 
Thanks, I appreciate it
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I connect my 3 x panels in Parallel to my AC200P. I get a much better return from them all day this way.