Quote:
Originally Posted by Bill
Bob is right. The numbers associated with solar panels are a bit tricky to work with. If a panel is putting out 4.65 amps, then 4.65 amps is what will come out of the controller and into the battery. The purpose of the controller is simply to reduce the voltage to whatever the battery can accept. Sadly, the extra voltage is simply wasted.
However, there is way to beat this. The behavior Bob and I described applies to a simple PWM controller (which is what you and I both have). There is a magic controller called MPPT that will convert the excess voltage to more current. It is considerably more expensive, and at the power levels being discussed, probably isn't worth the added cost. But we have had discsussions of MPPT controllers on this board - you can look them up with the Search tool.
Your post describes consuming almost all of the 160 watts of solar power as soon as it is generated - laptop, etc. Realistically, the small amount of power that is left over - and then, only under optimum sun - won't do anything to recharge your battery from any discharge that it undergoes. You are right, the solar power will substitute for power that would otherwise come from the battery, and so the battery will last longer. But you are right again in saying that the furnace blower, as well as lights and other loads, will still come out of the battery. So don't expect magic results here.
Way back in the very early days of the Solar Power forum, Rocky Mountain Ray did a real nice installation. He dry-camped high in the Rockies (perfect sun every day!) on a regular basis, and he was an electronic gadget guy as you are. He installed, as I recall, about 300 watts of power, which allowed him to do what he wanted. You might consider digging up his story.
The owners of Northern Arizona Wind and Sun are technical guys, and their web site has a real nice technical section that is devoid of advertising hype or product-pushing. It is also technically accurate and honest, without the "wisdom" that comes from somebody's brother-in-law's cousin. It is located at www.windsun.com. Their goal is to make a smarter customer. I have learned more from this site than from anything else on the web.
They also have a store, separate from the tech site. It is located at store.solar-electric.com. (They also have a walk0in retail store.) I recommend them, having owned a bit of stuff from them. Their prices are quite a bit lower than other sources. Not to be a wet blanket, but you could have built the same system for about $350 less.
Meantime, welcome to the solar family. Since there aren't many of us, we will all be watching for your experiences and reports.
Bill |
Hi Bill, thanks for some great insight and the howdy, there are tons of great people on this site, it's a joy to plop down at my PC and spend quality time enjoying all things RVing and TM.
On expense, yes I realized upfront the option I chose was NOT the cheapest, not even close. I have read through the solar threads, saw the excellent job Wayne did with his two panels that have the same power mine do for about 1/3 the cost of what I am doing.
I really like the portable aspect of the panels I ordered and the ability to simply add more kits to get from 80w to 320w setup. I realize this isn't rocket science to do that with any solar setup, but it's just a bit easier with these turnkey kits.
The CEA Solar rep has been extremely helpful and I found he's well known in RV solar solutions. He even answered his phone at 7:30 PM on Saturday and was courteous and kind in taking whatever time it took to answer my questions. I was pleasantly surprised.
On the actual electron dynamics that occur once the solar panels are connected and supplying power is a bit of a mystery to me and I haven't asked about this yet, so I will now. Obviously I have lots to learn.
I wondered with these PWM type controllers, how is power allocated when the panels are active. Initially the main question that I have relates to what I believe you touched on in your previous post.
Assuming the panels are in full sun and connected, with a load being applied inside the RV that is LESS than the output capacity of the panels:
1 - Can the system both charge the batteries AND provide power as pass-through energy to devices/appliances?
2 - Does the power that's output out of the controller ONLY come from the batteries? (IE - It never can be directly output from the solar panels to any device OTHER than the batteries.)
Ok then if question 1 = NO and 2 = YES then it seems a simple analogy could be that my batteries are a water tank. The solar panels are like a hose flowing IN to the tank. My appliances are like a drain flowing OUT of the tank. IF I have more water coming IN throughout the daytime (active power state for panels) will my batteries remain and be fully charged at the end of that daytime period? Is it that simple?
I imagine it's much more complicated than this but this might get me on the right track for now.
Thanks!
Bob.