acoleman43 -- instead of buying all new panels, why not just buy three more of the 165W panels you already have? 165*9=1485W That's a decent system. I assume, of course, that you've done the due diligence to ensure everything is going to fit on the roof. Review my lengthy thread on how I went through the decision process if need be--hopefully it helps. https://gdrvowners.com/forum/solar/1...n-2019-315rlts
What I'm suggesting is three strings of three panels and then put the three strings in parallel. As previously documented, three of the 165W panels in series gives a VMP of 50.31V. That's enough of a spread (IMO) between the 31V minimum previously calculated. Sell the 400W panels and you won't have to spend as much time on the couch.
The reason I keep harping on this is because of the previous post's question about putting all the proposed 24V panels in parallel. The VMP of the Newpowa panel is "only" 33.54V. If all of the panels were in parallel you'd have the exact same problem with very little "head room" between where the MPPT starts charging and where the panel likes to operate.
Some readers may be very confused at this point and I understand. If we could all gather around a monitor and watch in real time the actual power going to the battery with various configurations there'd be instant clarity on why having some range between the MPPT's starting voltage and the VMP is beneficial. Especially on marginal solar days where there's considerable overcast or in the winter with no ability to tilt and aim the panels at the low-in-sky sun.
Let me beat this point to death with the example of my system. The Renogy's Vmp is 17.7V. I wired two in series so they now should operate at 35.4V -- an excellent spread from my nominal battery voltage of 13.3V and MPPT starting voltage of 18.3V.
Below is an actual graph of my system's performance. You probably know by now that I have six two-panel strings (2 100W panels in series and then six of those strings in parallel). The dips in the middle were probably due to clouds passing over the camper. The key is the MPPT tried to keep the voltage at the Vmp of the panels. Wire panels in series and the target Vmp voltage of the MPPT increases.
I hope this helps...
What I'm suggesting is three strings of three panels and then put the three strings in parallel. As previously documented, three of the 165W panels in series gives a VMP of 50.31V. That's enough of a spread (IMO) between the 31V minimum previously calculated. Sell the 400W panels and you won't have to spend as much time on the couch.
The reason I keep harping on this is because of the previous post's question about putting all the proposed 24V panels in parallel. The VMP of the Newpowa panel is "only" 33.54V. If all of the panels were in parallel you'd have the exact same problem with very little "head room" between where the MPPT starts charging and where the panel likes to operate.
Some readers may be very confused at this point and I understand. If we could all gather around a monitor and watch in real time the actual power going to the battery with various configurations there'd be instant clarity on why having some range between the MPPT's starting voltage and the VMP is beneficial. Especially on marginal solar days where there's considerable overcast or in the winter with no ability to tilt and aim the panels at the low-in-sky sun.
Let me beat this point to death with the example of my system. The Renogy's Vmp is 17.7V. I wired two in series so they now should operate at 35.4V -- an excellent spread from my nominal battery voltage of 13.3V and MPPT starting voltage of 18.3V.
Below is an actual graph of my system's performance. You probably know by now that I have six two-panel strings (2 100W panels in series and then six of those strings in parallel). The dips in the middle were probably due to clouds passing over the camper. The key is the MPPT tried to keep the voltage at the Vmp of the panels. Wire panels in series and the target Vmp voltage of the MPPT increases.
I hope this helps...
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