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I am building a 12v system for an offshore sailboat. Because of complicated/limited space I would like to use two 175w mono (Vmp 17.95V/ Imp 9.75A), and a single 100w mono (Vmp 20.4v/ Imp 4.91A). All wired in parallel, I would end up with a 438w (17.95v*24.41A) system going into a 500ah 12v bank. Is this possible and which Victron MPPT controler would comfortably handle the job?
You could have the two 175W panels in parallel, but mixing different types is a bad idea. You could end up with one or the other odd one backfeeding one another. Worst case is the pair of 175W panels backfeed the 100W panel with 350W and set it on fire.
The only real choice here is to have the two 175W panels on one controller and the 100W panel on its own controller.
The 100W panel would do just fine on a MPPT 75/10 and the two 175W parallel pair can go with a MPPT 100/30.
Thank you for the very clear and concise answer. Fire bad, especially on a boat.
Now, how do two controllers get hooked together so we can see the total charge to the batteries?
Just connect them, if you dont have place take usb. When it sends data to gx you will see all. But its better to put in serial same panels, bigger voltage, less ampers, les voltage drop and better efectivity. Br
This is a very helpful article when setting up your solar panels. It explains series and parallel connections, and has pictures to help visualize how each way can effect the whole array.
https://solarpanelsvenue.com/mixing-solar-panels/
In your case you would want to wire them in parallel to minimize loses, but you will lose a little power from the 100 watt panel because of the lower voltage on the 175 watt ones. About 22 watts. The whole array is only as strong as the weakest panel in the array. Make sure the voltage or amps are not more the the charge controller can handle. You would want one to handle at least 30 amps. I would recommend SmartSolar MPPT 100/30 or better, if you want room for expansion in the future. They also have Bluetooth connectivity so you can use the Victron app and monitor your system as well.
https://www.victronenergy.com/solar-charge-controllers/smartsolar-100-30-100-50
In series:
Total Voltage: 17.95 x 2 + 20.4 = 56.3
Total Current: 4.91 (weakest panel)
Total Power: 276.4 watts
In Parallel:
Total Voltage: 17.95 (weakest panel voltage)
Total Current: 9.75 x 2 + 4.91 = 24.41
Total Power: 438 watts
