Basic Questions on Solar Install

BFL13 wrote:

freetheheal wrote:
I'm finally getting rid of the generator and looking to install solar. Right now I have a 2000W inverter and 450AH of lead acid batteries. I'm looking at installing (3) 175W panels and an MPPT charge controller. I'd like to run my idea by the forum and make sure I'm not missing something.

My run from the panels to the charge controller is about 25'. From what I've found I should wire the panels in series and run a 10 gauge wire. I'm looking at the Renogy Rover 60 mppt controller and that can handle up to 140V which is well within the parameter of the open circuit voltage of the 175W panels which is 24.3V per panel and allows room for additional panels down the road if the need arises. Does anyone see an issue with this or something that I'm missing?

From the charge controller to the batteries I am going to run 8 guage wire (5') with a 60amp fuse.

And between the solar panels and charge controller I was going to mount a 10amp fuse (the solar panels optimum operating current is 8.62amps).

Does this seem like a good plan so far? Am I missing anything? Thank you for your input and help.

Three 175w with "optimum current" (Imp I guess) 8.62 means Vmp is 20.3v. Isc will be higher than Imp 9a? and Voc 24.3

So expected max amps to battery to decide wire gauge controller to battery: (panels aimed at high sun--flat on roof you get less but do worst (best?) case here)

3 x 175 = 525w with 10% heat loss = 472.5w lose 3% line loss (WAG on 25 ft #10 copper one way at 8.62a) = 458w input to controller. Say controller is 4% inefficient, so output is 440w

amps to battery no line loss:
440/12v = 36.7a
440/14.5= 30.3a

So yes, #8 is a good wire gauge for that run from controller to battery.

On a perfect clear day in May at 49N Lat, you could expect an AH haul of about 190AH with that set-up. So you should be good with the 450AH bank not to need the generator much in the sunny half of the year in the Lower 48 states.

A few cloudy days in a row though, and out comes the generator! In the darker and cloudier half of the year, you will need the generator more often.

You will do well with that set-up, but you can't change the weather, so hang on to the gen.

Do you mind explaining some of your numbers further? What are the numbers 12V and 14.5 represent from your equation 440/12V=36.7a and 440/14.5=30.3a? And what is the amperage telling me from those equations. Sorry if it seems like a dumb question I'm just not following all of it.

Currently if we're conserving battery power we can stay 3 days without using the generator and bringing the batteries down to 70% (so using about 45amps per day). But more then likely once we have solar we'll be using around 70amps a day running things we would wait to run until we were on generator power.