Setting up Off Grid Solar System with 3.3kwatts of solar panels

[sailor4life7777]

Hi guys I am setting up my offgrid solar system with 6x550 watt solar panels, 2 60amp MPPT solar charge controllers and 2x 24v x200AH lithium batteries.

I plan to take 3 solar panels and wire them in parallel and connect the 3 parallel panels to one of the 60amp MPPT solar charge controller. I will do the same with the other 3 solar panels and wire them in parallel and connect them to the other 60 amp MPPT solar charge controller.

Both 60amp MPPT solar charge controller will be connect to the 2 x 24V200AH lithium batteries (wired in parallel).

The batteries will be connected to a 3000watt inverter.

Does this sound like a good plan guys? What do you all think? Would you do anything differently?

Also how do I calculate what size cables do I need to connect the 60amp solar charge controller to the batteries, and do I need fuses and combiner boxes?

Thanks in advance guys I really appreciate it!!!

[donradcliffe]

You need twice as much battery capacity or you will waste a lot of solar energy.

Do all your calculations in watts, and things will be clearer. For example you have 3300 watts of solar, which can generate about 5 hours worth of power during a summer day, or 16 kwhr. Your batteries are about 1o kwhr.

Your controllers are rated at 2800 watts, which is a bit too small for your bank. I would go 25-30% oversize.

You haven't mentioned panel voltage. If you put 3 panels in series, you can use smaller wires to hook the panels to the controller, at the cost of a bit more power loss due to shading. You need to compare the controller maximum voltage to the series panel voltage.

If you put more than 2 panels in parallel to each controller, you should fuse against a shorted panel. It might make more sense to use 3 60 amp controllers and 2 panels per controller.

A wire sizing table will show you the gauge wire you need for hooking up the controllers to the batteries. I would use 4 awg unless you combine the controllers into one cable run.

[smac999]

What is the voltage of the panels? I would probably put them in series not Parellel.

[sailor4life7777]

Originally Posted by smac999

What is the voltage of the panels? I would probably put them in series not Parellel.

Yes I agree I think I will put in series they are Voc=49.9

[noelex 77]

What model controller are you planning to use?

[smac999]

Originally Posted by sailor4life7777

Yes I agree I think I will put in series they are Voc=49.9

If they are 50v then I would Parellel them. 150 v dc is dangerous. And is Likly too high for most controllers. . Most panels are only 20v. Which would not be high enough for the 24v bank.

[David B]

Originally Posted by sailor4life7777

Yes I agree I think I will put in series they are Voc=49.9

Gee, that's 150VDC running around in a saltwater environment (assuming your controller is up for it), plus you will have issues with shading of one panel, affecting the other two.

I would always run panels in parallel if I could not manage a controller for each.
Heavier cable for parallel is a small price to pay.

[CaptainRivet]

Originally Posted by sailor4life7777

Yes I agree I think I will put in series they are Voc=49.9

Definitely not in series, your voltage at 49.9V is high enough to keep in low amp range. Your 550W will deliver around 450W, so means 9A per panel or 27-30A if parallel. That’s fine.
You don‘t want 150V on your solar panels wiring on a boat in saltwater, NoGo. And shading is significant loss if you run 2 or 3 panel per MPPT in series. I would highly recommend to use 3x Victron 30/100 smart MPPTs and put 2 panels per controller
Yes you have too less battery capacity. If you run a 3000W inverter on 400AH that’s 0.7C rate, most cells (if not Winston) do 1C max but shouldn’t run frequently over 0.5C otherwise the lifespan shortens significantly and they get out of balance soon. Would definitely add a 3rd 200Ah, a 4th depends on your overall consumption.
And having some watts too much in solar is not too bad too, especially if it’s low light environment they will produce more or battery bank is faster full giving you the opportunity to run the watermaker, washing machine or hot water heater to use the energy available from solar.