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Old 09-22-2010, 12:03 PM   #15
Join Date: Sep 2010
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Originally Posted by leadman View Post
My point on posting about the Harbor Freight system is to let others know about this complete system that is easily set-up with nothing else to buy. It also includes 2 12v flourescent lights that plug into the controller along with a plug-in wire with adapters to charge different devices. It has a USB port, 3v,6v,9, 12v sockets on the controller to run or charge devices.
This is not just the panel.
Granted to output is not large but with just 2 batteries for our coach it tripled the time we have before we have to start the generator to charge the batteries.
I think this is pretty good for $140.00.

Yeah, that's not a bad price for all that. I guess for occassional use just to extend your generator run times it works. If you could put a rotating assembly under it so you could direct it into the sun from morning to night it is SO worth it! You double your output. Dunno how easy that would be though in your set-up, or if it would even be worth it for occassional use.

I currently set up on the ground for my extended stays as I try to park in the shade in desert areas. If I spent more time in cooler climes, I'd probably take the time to set up a rotating assembly similar to yours for the roof.

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Old 09-22-2010, 02:20 PM   #16
Join Date: Sep 2010
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Sorry Bryan, I gotta disagree then with your insistence that power, or wattage, is the primary interest for the battery charging. This isn't just simple semantics, it's two entirely different ways at looking energy flow through a system.

Wattage is simply Volts X Amps.

The reason that wattage isn't as relevant as amp-hours, is that the batteries' voltage is more or less consistent within a few working volts, as long as the voltage is sufficient to push the coulomb of charge into the battery. So charging a 12 volt battery with a 28 volt, 5 amp charger will still only put 5 amp/hr charge into it. However, a 14 volt, 10 amp charger will fill that battery twice as fast, even though BOTH are nominally rated at 140 watts.

The amperage is the actual measure of the amount of electrons moving in or out of the battery, and maximizing that AMOUNT should be the primary goal.

A solar panel is just a nice flat charger. Wattage rating being equal, the one with a better amp rating just will charge faster. It has to. Now this would not be such a big deal if you are hooked up to mains power 24/7. But since the total number of hours of sunlight is fixed each day, you want maximum amps flowing into your batteries each hour. The total WATTAGE is irrelevant once the voltage surpasses the charging threshold.

Granted, the difference may only be an amp or two between two similarly rated panels, but when boondocking every amp-hour counts!

It seems you are primarily concerned with the proper measure of wattage through the system. That's fine, but obsessing over the exact amount used, and needing to be replaced is irrelevant if you don't have the solar capacity each sunny day to replace it. That's why I believe THAT should be one's primary concern.

Once you have sufficient capacity, then investing in a $400 MPPT controller starts making more sense. But if you are sucking 50 amp/hrs a day out of your pack, but only replacing 25 Amp/hrs with your 45 watt panels, an expensive wizz-bang controller will not make up for that. That's just simple Conservation of Energy Laws! Invest in more panels first.

As for "practice outside the norm", aside from following basic wiring and electrical codes, I wasn't aware that there was a government standard for solar panel installation on an RV. I will agree, I've seen some installations alot better than others. But one has to look at HOW they will use the panels to decide on the best configuration.

For example, my panels get set up on the ground so I don't have to park in 110degree desert sun to get juice. I can orient my rig however I want for comfort without sacrificing sun exposure. From there, the wires go through my Whatt's up meter so I can see my daily energy production, then an external weatherproof charge port I designed, then through a safety fuse and onto the battery.

DEFINITELY not standard, but for me, far more flexible and useful without sacrificing safety. I understand some people are far more obsessed with "practices and standards" than actual usefulness. They make terrific bureaucrats, code inspectors, and government officials, but lousy innovators, IMHO.

Speaking only for myself, I didn't strike out for the freedom of the open road full-time so I could deal with more bureaucratic control that contributes nothing to innovation, performance or safety.....

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Old 09-30-2010, 05:01 PM   #17
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In my shopping I have found a $75.00 per amp. or 12 watts is a good buy; No need to write a book about it. You are smart;;
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Old 09-30-2010, 06:06 PM   #18
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I'd like to comment you for your resourcefulness and creativity. That sure is a well thought out solar system.
2007 Newmar DSDP 4023
Discovery is seeing what everyone else has seen and thinking what no one else has thought.
If you want to see what man made go East; if you want to see what God made go West.
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Old 10-01-2010, 08:56 PM   #19
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Originally Posted by bachler View Post
In my shopping I have found a $75.00 per amp. or 12 watts is a good buy; No need to write a book about it. You are smart;;

$75 for 12 watts comes to $6.25 per watt. That's not a good deal, that's a solar rape!

Solar Panels - Sunelec : Solar Panels 78/W, PV Systems $2.40/W has complete panels for under $2/watt. Mine was on sale for $1.67. DIY panels are under $1/watt.

$6+/watt was good price in 1980, but they have come down quite a bit. You just gotta look around. But so far, I haven't found a steady source cheaper than the guys above....

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