List out what I need

[kyonu]

If it were me, I'd call Nothern Arizona Wind and Sun, tell them what your doing and buy what they tell me to buy.

http://www.solar-electric.com/

The problem is they'll ask you first how many panels and since you don't know it's very hard for anyone to advise you specifically what to buy.

If anyone can, they can.
Bob

I'm thinking about that Bob, but I'm nowhere near AZ for an install if I want to do it professionally.

Unfortunately, I looked at my new Class C yesterday, but it was the biggest rain storm San Antonio has seen all year (actually in the past 3 years) and we got totally flooded out so I couldn't measure the roof. I will have to get that information on the fly next time when I go to pick her up... Sigh.

 

[AuricTech]

Before you start designing your system, I suggest that you use a Kill-A-Watt meter to measure how much power your various loads actually use. The nameplate rating on most devices seems to be little more than a wild guess. For instance, you may find that the nominal 75W rating for a laptop computer actually averages out to 30W power use. Use it for 10 hours a day, and that's the difference between expecting to use 750 Watt-hours (and sizing the rest of your PV system to account for that load) and actually only needing to use 300 Watt-hours. You can use a DC clamp-on ammeter to measure your RV's 12VDC loads.

Next, look at conservation. The cheapest PV Watt-hour is the one you don't have to produce.

Once you have a handle on how many Watt-hours your loads will use in a day, then you can calculate battery bank capacity. Ideally, you'll cycle your battery bank down to about 25% depth of discharge (DOD) in routine use, with occasional dips to 50% DOD. It's not a good idea to oversize your battery bank, because that makes it too difficult to recharge it fully. Keep in mind that your inverter will also be a load for which you'll need to account. Taking your proposed 12V/675Ah battery bank down to 25% DOD would provide about 2000 Watt-hours of energy. That's a pretty hefty power requirement for a Class C RV; conservation could cut your requirements by half (or even more).

After sizing your battery bank, you're ready to calculate how large your PV array needs to be. Over at the NAWS forum (where I also post as AuricTech), the rule of thumb is that you want somewhere around a 10% charge rate, assuming four hours of "good sun" on average. Since your panels will generally not produce their rated power, the folks at the NAWS forum tend to use a derating factor of .77 (i.e., multiply your PV array's rated Watts by .77 to estimate how much power your array will actually produce).

Assuming that you go ahead with your 12V/675Ah battery bank, here's how I would calculate the required PV array size to keep that battery bank properly charged:

(14.5 charging Volts * 675Ah battery bank * .10 charging rate) / .77 derating factor) = 978.75W PV array

As you can see, it all starts with a good calculation of loads....

 

[kyonu]

That's some awesome info Auric! I understand it's hard for batteries in larger arrays to charge, but I'm more or less future proofing my setup as much as I can. I will definitely browse that site, I was hoping to find something like it!

My biggest concern, however, is all the add-on items required for a solar setup. Is there a list somewhere showing me all the parts so I can get them on order? You know, fuses, panels, cables, etc. All the little things you never read in solar installations reviews.

 

[TucsonAZ]

There's a lot of info to weed through, it's frustrating. Quick bullet point style:

1) If you're over 400 watts, get an MPPT.
2) If you're using an MPPT, get grid tie panels, in other words, 24v versus 12v.
3) Think about doing a 24v battery bank and inverter, the inverters are far happier and you can use smaller cables.
4) Some type of cut off between panels and CC, I used breakers.
5) No breaker needed from CC to batteries, that's to comply with home "code", not needed.
6) Panels, to breaker box/combiner/switch, from there to CC, from there to a breaker terminal sized for your inverter (the other terminal on the breaker goes to the inverter) and double up lugs on that terminal and continue to the battery bank.
7) Avoid too many parallel connection.

Thanks all I think think of for now, I just put an extensive system on my van and did a TON of research on it! The Midnite 150 was great, got it new on eBay for $450 shipped, DC QYI 125v 15a breakers in a box of 12 for $45 shipped.

 

[wagoneer]

8 batteries WOW. Makes me wonder how I get away with only 2 running a fridge and all my TV/radio/computer needs, my only advice is to keep it simple. The learning curve will get expensive.

 

[kyonu]

There's a lot of info to weed through, it's frustrating. Quick bullet point style:

1) If you're over 400 watts, get an MPPT.
2) If you're using an MPPT, get grid tie panels, in other words, 24v versus 12v.
3) Think about doing a 24v battery bank and inverter, the inverters are far happier and you can use smaller cables.
4) Some type of cut off between panels and CC, I used breakers.
5) No breaker needed from CC to batteries, that's to comply with home "code", not needed.
6) Panels, to breaker box/combiner/switch, from there to CC, from there to a breaker terminal sized for your inverter (the other terminal on the breaker goes to the inverter) and double up lugs on that terminal and continue to the battery bank.
7) Avoid too many parallel connection.

Thanks all I think think of for now, I just put an extensive system on my van and did a TON of research on it! The Midnite 150 was great, got it new on eBay for $450 shipped, DC QYI 125v 15a breakers in a box of 12 for $45 shipped.

Makes sense! I will definitely be doing 24v; I'll probably have over 700 watts of solar. I'm trying to find a good, complex diagram that shows all the pieces, and so far have found few. How do I judge what cables I'm going to need? I may end up buying them after the fact anyways, but the info would be nice.

@Wagoneer:

Well I'm going to be in a Class C with someone who will be working during the night hours at home. I need a nice charge to make her happy! 8 in a Class C shouldn't be *too* bad, but atm I'm only getting 6.

 

[kyonu]

UPDATE: Well, I have time to get all this stuff thankfully... As the dealer cannot order parts from other people than their own, and want outrageous prices from their own warehouse, I will piecing this together part by part over time, probably starting off with a single 125ah battery and 100w panel to begin small and learn my stuff.

No rush now! Thanks all for the help.

 

[highdesertranger]

nothing wrong with starting small, that's how I started. it will give you hands on experience and knowledge that will pay off in the future. highdesertranger

 

[TucsonAZ]

Small is a fine idea, the trouble is thinking you're going to start small and add because needs change with larger systems. Also, call local solar installers and as around, I got my new SolarWorld panels for $0.69 a watt with very little effort.