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Author Topic: What's Best Solar Panel for Coach?  (Read 1157 times)
NJT5047
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« on: June 03, 2007, 07:43:32 PM »

Just spent a pleasant 5 days dry camping at a music festival. 
The only nuisance of the week (of a mechanical nature) was seeing the house batteries slowly go down.  They never dropped below 12V, but this is still a "issue" in my retentive mind.  We were parked in a  non-genset area so using the generator was not cool (not that the genset "rules" were of any concern to one of my neighbors).
Seems as though the thoughtful application of solar panels would be a resolution to my battery discharge issue.   Such that it is.  Actually, the "issue" is related to Terri's resistance to my power management suggestions.   Wink
Solar panels appear to be expensive items.  Looks like a lot of variation in quality.  Also have a space problem on the roof...ACs, sat, vents...etc.   Maybe use multiple smaller panels?
Is it feasable to apply isolated 12V panel (s) to each 12V battery  in order to keep the the 24V bank charged?  I run a good bit of stuff (not constant load) that runs off of a 24V inverter, but haven't seen any 24V panels...??  Is there any such thing?
What is the most bang for the bucks in RV solar panels?
I'm interested in the negative and positive aspects of solar power.
Any info would be most appreciated!  JR



 
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JR Lynch , Charlotte, NC
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Jerry32
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« Reply #1 on: June 03, 2007, 08:26:34 PM »

You can use solar panels just like batteries in series for 24 volt operation. they also need to be matched for output. Jerry
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« Reply #2 on: June 03, 2007, 09:45:26 PM »

Solar is expensive @ 3 buck a watt ... you may find it cheaper but it's still not cheap. If your bus is set up like mine, house fridge, plasma TV, computers, microwave, etc. you will need around 650 watts to 800 watts of power, for the solar cells to keep up with your power requirements.

I have the same problem with my wife  Huh .. she just doen't quite get it   Shocked... but she is getting better  Grin
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pvcces
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« Reply #3 on: June 03, 2007, 10:48:29 PM »

We went with the narrower panels, about 16" wide and 51" long. One reason was that it made it possible to put a panel on each side of the roof and leave a good sized walkway between them.

We are using four panels of 55 watts, each, but we could use two more.

If you use an MPPT controller, the panels will only need to be high enough voltage, not matched to the batteries. A common setup uses 24 volt panels charging into 12 volt systems. That's what we have and it works good.

Unless you do much better that I have recently, you're going to find most panels up around $5 per watt. The controllers aren't cheap, either. However, our coach sets between trips, but the batteries are always up and raring to go when we need them, even in winter.

You can figure with current technology that panels are rated to produce about 100 watts per square meter. You can tell the voltage by counting the cells and looking at their sizes. 4" square cells are about one watt each and around 1/2 volt for about 2 amps.

They usually have something like 33 or 36 cells set up in three or four rows. 33 cell panels can be a little marginal at high temperatures, so a lot of them are 36. A lot of the wider panels have twice the number of cells.

The reason that the voltage on an MPPT type controller is that it matches the voltage of the panels to the system and should get you the best charge rate.

For what it's worth.

Tom Caffrey
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Tom Caffrey PD4106-2576
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« Reply #4 on: June 04, 2007, 07:08:27 AM »

Tom

Are these any good from Harbor Freight - thinking about 2 sets in series for my 24 volt needs  (90 watts)

about $4.42 per watt

Pete RTS/Daytona
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Dale MC8
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« Reply #5 on: June 04, 2007, 09:39:46 AM »

JR; there is a lot of good information out there on the Alternate Energy websites.

Many of them are almost textbook like in their directions and make the assumption that some of their customers are totally ignorant about solar power and electricity, then try to correct that. Of course you will also get a lot of "Hippy" information but that has nothing to do with how their systems work.

When you are talking costs, you have to think in the long run. Right off the bat there will be a large cash outlay but after that, only battery replacement costs [hopefully.]

HTH, Dale
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« Reply #6 on: June 04, 2007, 02:04:45 PM »

 I have 880 watts on my roof(8 -110 watt Panels) two 400 watt wind turbines and I could use more but, I am all electric so need to run the gen set about 1 hr a day also, unless it is windy     Merlin
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NJT5047
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« Reply #7 on: June 04, 2007, 05:38:57 PM »

Wind turbines....believe it or not, I looked at those too.  Had some experience with a wind generator on a sailboat.  Not an especially good experience.  Always too much wind or too little.  Sucker was noisy. 
Must admit that considerable improvements have been made to the blade design.  Newest designs are much quieter so I'm told. 
Don't believe I'd have enough wind to be useful here in central North Carolina. 
All I'm wanting to operate is the TV and sat receiver, and the LED palm tree.  LP operates fridge, stove, and hot water. 
The only constant loads are LP monitor, radio, and fridge 12V control power.
If my calculations are correct, the TV, sat receiver, and palm tree would be a 6 amp load @ 24V (inverter)? The LCD TV and sat receiver only draw .5 amp @ 110VAC according to my load center....not much.  But, after two or three days without charging, my two 8Ds start to get down to 12V...and I get antsy.
Looks like it may be cheaper to install 200 or so watts of solar to sorta slow the discharge....or watch less TV?  Obviously, the LED palm must be lit for a proper party atmosphere.   My needs are not great.
Looks like if good quality panels are used, once they're installed, it's free electricity after that.  Batteries are not at all free.   My house batteries are going on 4 years old.   Probably have to replace them next year.  Seem to be OK now.
Pete asked a good question...are the Harbor Freight panels a good buy?   There are some Kyocera panels on Ebay, but they ain't cheap.  Looks like quality items.     
Thanks for all the info,  JR

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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”

Ayn Rand
pvcces
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« Reply #8 on: June 05, 2007, 09:31:51 PM »

About the Harbor Freight panels: a good panel like a Kyocera will have something like a 100 watts a square meter and carry a 20 year warrantee. They should be able to stand 1" hail strikes at 52 MPH. Lower efficiency panels will take up too much room for an RV.

I really don't know what source Harbor Feight has, but I doubt that they make them. Perhaps you can get the specs from them.

The major manufacturers are right up front with the specs, because that's what they're selling. The panels should have a label with the information that you need.

That's about all I can offer on Harbor Freight; I've never looked at their panels.

For what it's worth.

Tom Caffrey
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Tom Caffrey PD4106-2576
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Ketchikan, Alaska
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