More equipment and lots more questions

DebbieK · June 2023

I asked some questions about 1 1/2 years ago and got some answers here and I hope you guys can help me again.

I started with 4 100 watt Renogy panels, a Renogy MPPT40CC controller, a Model MT-5 remote meter, a Xantrex PROwat SW 2000 Sine wave inverter (which is only compatible with a 12 volt system) and 2 VMAX SLR125 AGM batteries. The batteries were over 7 years old and could not hold a charge for very long, but the system did/does work.

I recently got 4 more 100 watt Renogy panels and 4 new VMAX SLR125 AGM batteries.

Let me again emphasize that I know next to nothing about electricity, amps, wattage and volts, but I am good at following directions and diagrams. The last year and half haven't made me any smarter (in fact, I think I've lost ground).

So, it appears to me that my Renogy MPPT40CC controller will be inadequate to handle the potential amps that 8 100 watt panels could produce, is that correct? I've been reading topics here and I've seen comments that recommend using more than one controller, one for each set of panels. Since I may want to add 4 more panels in the future, wouldn't it be better to get a bigger controller to begin with? If I did want to use multiple controllers, would I just tie them together and then into the batteries in the same place? Wouldn't a 100 amp controller be too small for a 12 panel array also? What controller would you guys recommend?

If I do get a larger controller and run all the panels into it, is it okay to have two sets of four parallel wired panels stepping down to one pair of inputs? And how does upsizing like this potentially affect my fuses? Do they need to be larger, too?

I know these seem like really dumb questions, but I'm trying to do this the smartest and safest way possible with really rudimentary knowledge and skills. Any help and advice would be welcome, and thank you guys for being so supportive!

Debbie

Dave Angelini · June 2023

Hi ! You kind of have to decide if you want the next size up charge controller or change the inverter and the system to 24vdc.

your mppt says "Max. PV Input Power: 12V/520W, 24V/1040W" if I am getting good search data.

Yes to your question on it being OK to parallel and you will need more fuses of the same value.

If it were me I would wire the battery to 24v, get a 24v inverter, and use the old mppt with the 8 panels in a 2 X 4 wiring. You will have more room to expand later and the wiring can be smaller. See what the others say here. Good Luck

DebbieK · June 2023

Dave:

Thanks for your reply. I've decided to go with the Renogy Rover 100 so I can expand to 12 panels (if I ever can afford it). Will keep the 40 and maybe set it up with some cheap panels and inverter (and the old, bad batteries) to run a small pump. Believe it or not, I started with all this insanity in an effort to keep fish alive for when I lose power. And, it would be nice to be able to intermittently run a refrigerator or AC during hurricane season.

Thank you again!

Debbie

BB. · June 2023

One big issue with solar panels is how well you bolt them down (or store in basement during storms, etc.).

Solar panels are typically rated for 50-100 pounds per square foot of wind loading... For a typical 100 Watt Renogy panel:

https://images.thdstatic.com/catalog/pdfImages/27/2772d35f-f407-489c-a603-159cfd67e7d4.pdf

Dimensions Front Glass Frame Monocrystalline 42.4 x 20.0 x 1.4in (1076 x 509 x 35mm)

42.4 inch * 20.0 inch * 1/144 sq inches per sq ft = 5.86 sq foot
5.86 sq foot * 50 lb per sq foot wind loading = 293 lbs of wind loading per panel

The above is not an "official" engineered wind loading calculation--Just an idea of the forces you are looking at (and in a hurricane, you local code may require 100 lb/sqft or more wind loading calculations).

For a better system design--A good starting point is to use a Kill-a-Watt (or similar) meter to measure the energy usage by your aquarium system over 24 hours (kWatt*Hours). Starting with this number, you can pick the right battery size and solar array to support those loads (based on your location nearest major city).

-Bill

More equipment and lots more questions

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