Just when I think I got it...

[jflorey2]

And then get a step down converter that will go from 48v to 12v?

Yes. 48V to 12V won't cost any more than 24V to 12V.

So with 48 volts, then would this charge controller be the size I'm looking for?

That would work but it's overkill. Since you are at twice the voltage you will only need half the current. So (1000 watts / 50 volts) = 20 amps. You can get the Midnite Kid controller (an excellent MPPT controller, 30 amps) for $280.

[monicaj]

Mike, thanks! I hadn't even thought of using generator run the washer and well pump. That opens up some paths.

[monicaj]

Yes. 48V to 12V won't cost any more than 24V to 12V.

That would work but it's overkill. Since you are at twice the voltage you will only need half the current. So (1000 watts / 50 volts) = 20 amps. You can get the Midnite Kid controller (an excellent MPPT controller, 30 amps) for $280.

You just made me feel good (sane). I was actually thinking the 60 amps would be too high but didn't want to risk looking stupid by asking about in case I was off base. The reason I wasn't sure was because I got confused as to why you'd still use the total amount of watts of the panels in the calculation for CC size if the panels were going to be hooked in series (making the array 280 watt 140v).

So that means the wire going between the charge controller and battery can be smaller, 30amp or larger...

I want to thank you guys so much for helping me learn. Going to take the next couple days and review all the information you've given... and also try to study watts, amps, and volts to know what they really are.

[jflorey2]

You just made me feel good (sane). I was actually thinking the 60 amps would be too high but didn't want to risk looking stupid by asking about in case I was off base. The reason I wasn't sure was because I got confused as to why you'd still use the total amount of watts of the panels in the calculation for CC size if the panels were going to be hooked in series (making the array 280 watt 140v).

So that means the wire going between the charge controller and battery can be smaller, 30amp or larger...

Exactly. There are several benefits to going to higher battery voltages.

[monicaj]

And then get a step down converter that will go from 48v to 12v?

So with 48 volts, then would this charge controller be the size I'm looking for? MPPT 12v/24/v/48v, 60Amp, 150V pv input...
https://www.amazon.com/Hxengy-Solar-...rge+controller

I don't know why I thought I needed the CC to handle only 150V pv input... It has to handle at least 179.2v...

This stuff makes my head spin demon style.

[jflorey2]

I don't know why I thought I needed the CC to handle only 150V pv input... It has to handle at least 179.2v...

Two panels in series will give you 70V. Your 48 volt battery will not need more than ~60 volts for equalize charging (2.5VPC.) Then add overhead for losses and panel temp derating and you should be OK with two in series. Max voltage will be around 90 volts, plus some margin for cold morning startup. Since your charge controller is good for 150 volts it won't be an issue. (Even if you are seeing -25C temps in the morning, that will only add around 10-15 volts to your open circuit voltage.)

However you can also do four in series; the MPPT controller will then drop the voltage for you. As you correctly realized above, in that case you will need a significantly higher voltage rating for the MPPT controller. This probably isn't worth doing unless your panels are very far from your charge controller and the wire is getting too expensive.

In general, one 36 cell panel will give you about 18 volts, and that's enough for one 12V battery. The Suntech panel is a 72 cell panel so it will handle two 12V batteries in series (or 4 6V batteries.) Two in series then will handle 4 12V batteries in series.

[Mike90250]

Wow 180V Check the specs of the magnum-energy-pt-100-charge-controller and see if it can handle that, or if you need to use a Midnight Classic 200.

[monicaj]

Thank you both very much!