Building an RV Electrical System? Read These!

[Xterabl]

Great! More info piling in. Thank you everyone for taking the time to post their info and analysis and engaging in good discussion.
My conclusion is that there are pros and cons to wiring series and parallel, and apparently there is not a clear "must do" approach.
Rather, decide based on your overall plan (e.g. if you're not interested in spending extra $$$ for MPPT controller (which allows one to maximize power for a restricted area), then don't wire in series).

For my full disclosure, I DO in fact have 2X 40W panels wired in series with a MPPT controller (Sunsaver 15A). Mostly, I wired in series based on simple assumption that power is generally better transmitted via high voltage/low current rather than vice-versa (smaller wire gauge required, etc.).
However, after installation, I did find that shading DID create more loss than I expected...but my "expectation" wasn't based on any kind of data or theory or comprehensive knowledge about the cell/diode configuration of my particular panels.

I was considering rewiring in parallel based on earlier posts; however, such rewiring is not quite "plug and play" with my current setup, and would require cutting wires, (re)soldering connections, etc.
While it would be interesting to compare the two configurations in terms of power loss as a function of cell shading, I think i will have to wait for a more compelling reason to rewire everything (But yes, I truly do wish I had that much free time!!!).
Again, thanks for the great discussions!

 

[Joe917]

Going back to the original post:
http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/ I would agree this is a must read mine of solar info.
I have no experience with smart gauge so will not comment.
I would add as must read:
http://www.pbase.com/mainecruising/boat_projects especially the battery cable section and wire termination
http://www.sterling-power.com/ A ton of reference material . If you order anything ,order through Defender.com, there is a significant saving.
http://www.bogartengineering.com/ You need a battery monitor that tracks amp/hrs this is what I use and recommend it. There are others.

I agree parallel wiring of panels is the best set up.
I disagree with the notion that many small panels are better than a few large panels. Small panels are far more expensive than large panels on a cost per watt basis.

 

[ScottReb]

Handy Bob is a great resource and a great guy. You can contact him and he will help you with whatever he can. He asks for nothing in return. He was a great help with setting up my last rig.

I agree with Joe, bigger panels equals better cost per watt. If you have the room...

 

[DiploStrat]

Some Comments

My recommendation to go with relatively more smaller as opposed to fewer larger is based ONLY on mitigating the impact of panel shading. More smaller panels is less cost effective than fewer larger panels.

The Bogart TriMetric is the gold standard. I actually have one in parallel with my Blue Sky controller and the results track very closely. In my case, the Blue Sky gives slightly better results as it is temperature compensated.

The wild card in this equation is the Smart Gauge. See the write up linked above: http://www.pbase.com/mainecruising/smart_gauge This beast is highly controversial, but does claim some clear advantages over time. Scholars REALLY differ on this.

Charles Sterling Sr. and Chris Gibson have strong opinions on battery charging in narrow boats, and thence, conventional boats, and thence RV's. They both agree, strongly, on the benefits of higher charge voltages and multi stage charging. (Sterling offers various charts and videos to make the case. This is a classic exposition on the value of high voltage charging: http://www.sterling-power.com/images/downloads/advancedcharging.pdf)

They differ on how to wire your boat or RV. I started out in the Sterling camp, with a Sterling Alternator to Battery charger and ended up in the Gibson camp with a smart relay. The big difference is that Sterling assumes that your alternator runs at too low a voltage and Gibson assumes the opposite.

If you are dealing with a classic, small system, say a 100Ah battery that you can mount under your hood, then a key controlled relay is probably all you need. You can learn how to do it here: http://www.expeditionportal.com/forum/threads/77503-How-to-make-a-cheap-isolated-dual-battery-setup-for-50

Move up to a larger battery bank, say 200+Ah, located at some distance from the alternator, say 20 feet, and things get more interesting. The key point for an RV (as opposed to boat owner) is that you are unlikely to ever run your truck engine long enough (say over six hours), often enough, to assure that your batteries get a full charge. This led me to install a combination alternator/solar charging system. In simplest terms, the alternator provides the bulk charge and the the solar provides the acceptance charge. To date this has worked very well with a 600Ah battery bank consuming about 125Ah per day.

As always YMMV, scholars differ, and a lot depends on pixie dust.

 

[dwh]

and a lot depends on pixie dust.

And magic smoke.

 

[DiploStrat]

Pixie Dust - Explained

Charles Sterling (Sterling Products) and Chris Gibson (SmartGauge) differ, strongly, on the best ways to wire up a charging system in a narrow boat and thus, by extension, a camper.

They do agree, strongly, on the merits of charging at as high a voltage as the battery will safely accept. In grossest terms, Sterling assumes that your alternator will only charge at about 13v and makes products which will increase this to over 14v. Gibson notes that most modern vehicles already charge at over 14v, and limits himself to simpler, relay based systems. He suggests that if your vehicle does not charge at 14v, you should address the issue for both the starter and camper batteries, rather than adding a system that boosts the voltage for the camper battery only.

Whichever way you go, Sterling has produced a very nice chart which demonstrates the merits of higher voltage charging and discusses the issue of surface charge. You can read it hereL http://www.sterling-power.com/images/downloads/advancedcharging.pdf