Is it worth it to add one more panel?

[SoFar]

I have 8 panels and have an extra one in the garage. the panels are 280W. Is it worth it to add one more panel?

It's about an 11% increase in power. (2240w vs 2520w)

my current system has a AIO 3000w inverter and 10kw in lifo battery 48v. My inverter uses about 60w of power and my loads are about 250w. Everything runs fine, except if we have a few cloudy days in a row. When that happens, my batteries don't charge back to 100% and I they will eventually drop at 20% and shut down.

Would that extra panel make that much difference?

 

[rodrick]

Over paneling is a common practice helps make up for low pv days just stay under max voltage for your scc adjusted for temps

 

[MichaelK]

Before that question can be properly answered, we need to know what the voltage of your panels is, and what the volt limit of your inverter is. Without those numbers, people are just guessing.

Are your eight panels 60-cell or 72-cell? A 60-cell is likely to be running at ~30.0Vmp, and a 72-cell at ~37.5Vmp. So, that works out to be 240V to 300V respectively. So, adding one more panel will bump those numbers up to ~270V and 338V respectively. If you assume your Voc is ~1.25X the running voltage (Vmp), that means a string of nine might max out around 423V or so?

What are your winter lows like? At freezing, that 423Voc number is likely to exceed 473Voc, which is higher then the limit of many AiO inverters. So, with the right panel, and the wrong weather, there's a chance you could short out your inverter, and start a fire. The colder it gets, the higher the voltage gets. Here's a string calculator to determine that. https://www.midnitesolar.com/sizingTool/index.php Get the real specifications for your panels and equipment, and we can make a better estimation.

For cloudy weather, adding an additional 12.5% of capacity is not going to account for much. You really need to look at 100-200% increases in panel size to make enough in the rain.