# HELP, new to solar.

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Ok, bear with me, I'm pretty dumb here so speak to me in plain english that a child can understand. Not a lot of formulas and scientific lingo. A drawn out schematic in crayon will work wonders. I have a small cabin (bout 275 square ft) that I have been powering by generator for years. I was planning on getting 3 120watt 12v panels to help power it. I just recently came across 2 175watt 24v panels. With these I could get around the same amount of watts I am looking for, but with only 2 panels instead of 3. Less panels would be good due to my limited amount of roof space. I have a pretty good idea as to how a 12v system works and wires up. But, I don't fully understand about the 24v.
I know (or think I know, I may be wrong.) most controllers work with either 12v or 24v. And that the batteries can be wired for 12v or 24v. And, that I'll have to have a 24v inverter instead of 12v. Am I right??
If I am right, despite the fact that I'll have one less panel to worry about, would a 24v system be better than a 12v? What are the advantages/disadvantages of 12v vs 24v.

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Re: HELP, new to solar.

My favourite is "Practical Application of Euclidean Algorithms in Structural Steel Members". Lot's of fun formulas!

But completely useless to the question.

Yes, 2 x 175W = 350W which is pretty close to 3 x 120W = 360W. Not much difference there.

But when you go from 12V to 24V strange and wondrous things happen.
For instance, those charge controllers that work with either 12V or 24V: most don't work with both. If you're looking at the less expensive PWM type (please look up the terms; we have a glossary around here somewhere and we'd like someone to use it! ) the nominal system Voltage and the nominal panel Voltage have to match. This means if you have a 24V panel you can use a PWM controller with a 24V system. Otherwise you're basically wasting half your panel, so to speak.

The other option is to use the MPPT type charge controller, which is much more expensive and usually only found on larger systems. It can 'down convert' the higher panel Voltage to the lower system Voltage and 'turn the surplus into Amps' so to speak.

As for which is better, a 12V or 24V system, it all depends. Depends on what? Well here comes the oft repeated phrase: your loads.

You absolutely must determine what the purpose of this system is and get some real-world figures on how many Watt hours you need to supply. If you do it the other way you're in a state of "I've got this much power, now what can I run with it?" This usually isn't a good way to start.

Save yourself a lot of headache and wasted \$ and figure out what you want the system for first.
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Re: HELP, new to solar.

Thanks Cariboocoot. Maybe I'll just stick with a 12v system, since I half way understand it.
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Re: HELP, new to solar.
kf4yre wrote: »
Thanks Cariboocoot. Maybe I'll just stick with a 12v system, since I half way understand it.

For small system 12V has certain advantages. Like the large amount of 12VDC stuff available at RV supply stores which makes it easier to set up, use, and repair.
• Solar Expert Posts: 272 ✭✭
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Re: HELP, new to solar.

I'm a fan of high voltage panels & strings with a MPPT controllers and, high voltage battery banks. Nothing exotic about a 24 or 48 volt system. The more your loads the more a higher voltage makes sense.
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Re: HELP, new to solar.
audredger wrote: »

I'm a fan of high voltage panels & strings with a MPPT controllers and, high voltage battery banks. Nothing exotic about a 24 or 48 volt system. The more your loads the more a higher voltage makes sense.

Except for that one little threshold at 15VDC.
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Re: HELP, new to solar.
Except for that one little threshold at 15VDC

OK,? What threshold? I thought the threshold was between a 6 volt and a 12 volt Volkswagon... LOL
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Re: HELP, new to solar.
audredger wrote: »
OK,? What threshold? I thought the threshold was between a 6 volt and a 12 volt Volkswagon... LOL

Nope; not gonna 'splain it!

There are a lot of electrical experts on this forum: let's see which one of them comes up with the answer first!