Sizing panels to controller.

[Sereno]

I've looked around but could not find anything that helped. I'm in a 3rd world Caribbean island where the grid is really bad and very expensive. Everything has to be shipped in with high rates and customs so I'd REALLY like to get this right. Depending on local talent is NOT an option.

I've been upgrading my solar systems to get off the grid. I have a gen. if needed.

I replaced my large 10 year old 120 V inverter with an Outback GS8048A with all the extras. This is a 120/240 V unit.

My 2 Outback MaxFlex 60s are connected to this inverter along with a communications tie so the inverter can somewhat control the controllers. When the batteries are charged the energy goes directly to the loads that can be rather large during the day but very little at night.

3 banks of 245 Ah batteries. 48 V system.

So far so good and everything works.

I need a larger solar panels/system but only have room for a max. of 15 panels.

I was looking at: Suniva 335 W / 37.7 V / 8.89 A panels.

The guy that I was/am working with tried to sell me these before but when I asked about them he said that they are too big and I'll fry my controllers.

I've tried working out all the math but after setting up the new inverter my brain is fried.

I'd really like to hear from as many as possible as to what you think is the best way to go and configure.

Thank you very much. Sereno

[sensij]

The Flexmax 60 can produce 60 A at 48 V... 2880 W of power. They recommend a max of 3000 W of panels. The controller will tolerate up to 150 Voc in the coldest conditions, although in the Caribbean, that isn't much of a design constraint. It is most efficient around 68 Vdc for a 48 V battery bank.

With the Suniva panels you selected, the max you could put on each charge controller is 3 strings of three panels (9 panels total), or 4 strings of two panels (8 panels total). In either case, with more than two strings, don't forget to use fuses in the combiner.

Since you have two CC's, and room for only 15 panels, the best layout would probably be three strings of three on one CC and three strings of two on the other CC. You might consider looking at 60 cell panels to see if they fit more efficiently into your space.

5000 total watts is probably about the most you can put onto your 735 Ah battery, assuming they are flooded, not AGM. That gives a max theoretical charging rate of around C/7.

[Sereno]

Thank you sensij. Very helpful. I'd like to hear from others too. Thank you.