Sizing my system base on Panels i already have.


New Member
So bought 8 second hand panels (3 yrs) but im trying to figure out what INVERTER, BATTERY and CHARGE CONTROLLER sizes I need for my offgrid system. I live in the South Pacific islands of Vanuatu. Any help at all is much appreciated. Don't care if its not perfect. Look at the image for panel details


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Solar Enthusiast
Well, you've got 2880w of panels there and all the sun you could hope for so really the sky is the limit. Really the question comes down to how much you want to spend but that should carry a 6kw system without a problem.

I'll start with the basics though...

How much power do you expect to use? (Inverter sizing)
How long do you want to be able to use that power? (Battery bank sizing)
How much do you want to spend? (Budget sizing)
If you run a 48v battery bank (most efficient for higher output inverters) you've got to figure at LEAST a 60a charge controller (which is usually about top end) for that much array, or even better do a 4s/2p on a pair of 40a controllers and have your panels spread out to catch longer sunlight (i.e. a string facing SE for morning sun and a string facing SW for the afternoon sun).

If you had all the moneys you could easily throw a huge Lith bank on there and have a 6Kw inverter, or a couple of 3Kw inverters providing split-phase power, or you could put in a smaller inverter for the lights and a radio and have enough battery to run it all year without panels at all.

Tl;Dr - Have you done a power audit? :)


Photon Sorcerer
There is a common (good) practice to "over panel" a system. Panels that are rated at 290w will get 290w for maybe one hour per year (unless it is cold a lot). In real life those panels should get about 250w during the best 2 hours of the day. So I would say, If you never, ever plan to get more panels, build a system slightly smaller so those panels can get it charged up quicker. If you think, "Some day I can buy more panels", then build a system that is a bit larger. It will work now, with less than ideal charging but will charger quicker after you get more panels someday. To me an ideal system is one that will charge up in one day or less of good sun. But on a solid overcast day, you will get only a fraction of a good day, so a larger battery system would be nice.

Batteries and panels are normally the easiest part to add to as a system grows. Some inverters can be "stacked" (running together as one) to increase inverter power. "All in one" systems have inverter, solar battery charger, and a grid charger together in one package. All in one units can often be stacked. So with existing panels, you could get a battery that you could larger grow and with a stackable inverter/charger, you could grow that later as well.

Look for videos about "DIY LiFePo4 battery build" and see if you think you would want to assemble a battery. You can get 2 times the battery for the same price if you assemble the cells and BMS. You need a few tools and a little knowledge but it think most people can pick that up if they study, ask questions, and watch several "good" videos. Will has some good ones.


Solar Addict
trying to figure out what INVERTER, BATTERY and CHARGE CONTROLLER sizes I need for my offgrid system.​
No disrespect to other posters info meant, but to me all I need to know is your budget tolerance. Not being flip or sarcastic btw. Filling in the other blanks is easy.

Two questions really:
  1. Is money an object?
  2. What are you using now?
I suppose knowing what you desire to power is important but you don’t seem concerned so I’m guessing you don’t have fantasies of running a big air conditioner or charging a Tesla