Solar panels

Slownsy wrote:
I was hoping to use existing cables and go to 24V with MPPT charger and ad a couple of new panels to existing.
Frank.

4 x 22.5 = 90 volts in series. Many MPPTs are good to about 100 Voc. some will do 150 Voc (at 25C/77F--and Voc goes up when it is colder, so pushing your luck at that if you camp in the cold.

Add another couple of new panels of what size? Two more 12v of any watts will be 2 x 23(say) = 46 more Voc, so total 90 + 46 = 136 so you could do it with an MPPT that has 150 Voc limit. 46Voc in a "24v" panel will be a single big one high 3xx watts. Not sure how you "match" for voltages doing it that way.

Getting up there in amps size of controller needed for that many array watts.

IMO since you get the same amps to the battery by leaving your existing set as is, and adding a second set as mentioned before, why do all that work? YMMV of course.

I was hoping to use existing cables and go to 24V with MPPT charger and ad a couple of new panels to existing.
Frank.

You can add a second set of panels with its own controller that goes with that set of panel specs.

Then set the (adjustable on each controller with many of them) charging voltages close to the same for the two controllers and wire them both to the battery bank.

They will add their amps so it is just as good for amps to the battery as having one bigger array and one controller.

Eg, in the Class C, I have a 275w panel with an MPPT and another set of three 100w in parallel with a PWM controller. The two controllers are each set to 14.6 Vbs, and add their amps as though it was one big 575w array. I can tell they are adding their amps by seeing the amps output showing on each controller's display and then look at my battery monitor and see the total amps showing there. Kind of neat.

I had three solar sets on the C for a while, but moved one set over to the TC we got.

Ok thanks all that helps, I was unsure if I could ad more panels and a larger charger, what is most important if adding other panels without the exact same specs, and how much difference is acceptable , as my panels no longer available.
Thanks Frank.

BFL13,

Nice find on the link. Ty.

naturist wrote:
Um, Given that the open circuit voltage listed is 22.5 volts, you reach the limit at 26 panels in series. The 27th puts you over 600 volts.

The "real" limit is the total Voc limit rating of your solar controller, which can be say 100 volts at 77F/25C. So you can string maybe four at 22.5 each in series. But then remember that Voc goes up with colder temps (and down with higher temps) so in the cold you could fry your controller if you are near the limit for 25C.

Um, Given that the open circuit voltage listed is 22.5 volts, you reach the limit at 26 panels in series. The 27th puts you over 600 volts.

While the Eaton manual has a lot of good information for large grid applications it may not be the best guide for smaller RV installations. Fusing both the + and - wires is one example. But it can trigger thoughts, questions and understanding.

This might be what you are looking for--it is not all about fuses. Scroll down to the diagrams of various ways they hook up the panels and how that affects things.

https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/fuses/bussmann-series-photovoltaic-fuses/bus-ele-an-10191-pv-app-guide.pdf

Voc is the open circuit voltage and adds for series connected panels. Isc is the maximum amps from a panel when using a PWM controller. Vmp (which is 17.9V, you have a typo) is the voltage at maximum power - ie 17.9V*8.38A = 150W.