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Old 02-10-2010, 11:58 PM   #1
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How much solar do I need?

I'm interested in setting up a free-standing solar panel for the purpose of charging my batteries and keeping them topped off. My usage is basically the lights inside the Bambi, the built-in stereo, and a laptop computer. Not really interested in watching TV, but wouldn't mind knowing what that would add to the demand/usage mix. Not being a math wiz, I know there are calculations to be made in answering this question, but I don't mind confessing my ignorance on the subject. Any advice, estimates, etc.?
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Old 02-11-2010, 12:20 AM   #2
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You might try buying a "Kill-a-watt" which measure the AC power consumption and calculating the difference between the total watt hours you use when you're using the trailer for a weekend and how much the converter uses some weekend when it's plugged in and no one is using anything.

You can estimate a lot of things but actual measurements trump guess work every time.

You'll also need to figure out whether this is summer time usage or winter (less sun power available), etc.
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Old 02-11-2010, 12:21 AM   #3
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Quote:
Originally Posted by ESCAPE POD View Post
I'm interested in setting up a free-standing solar panel for the purpose of charging my batteries and keeping them topped off. My usage is basically the lights inside the Bambi, the built-in stereo, and a laptop computer. Not really interested in watching TV, but wouldn't mind knowing what that would add to the demand/usage mix. Not being a math wiz, I know there are calculations to be made in answering this question, but I don't mind confessing my ignorance on the subject. Any advice, estimates, etc.?
Jerry and Susan

The answer to your question, is somewhat easy.

Add up all the current requirements that the various electrical systems will use, in amperes.

When you have that total, multiply it by 12 which is the DC voltage. That will give you the total watts you will be demanding.

Then divide that total by the number of hours that the bright sunlight will be available.

That basically tells you the total wattage that the solar cells should provide.

You must also consider that if the sun is not available for a couple of days, or so, then the battery or batteries remaining power, could become very small, if any.

Certainly adding an additional battery or two, allows you to take more advantage of the suns energy that will stored.

Actually, there really is no positive "this is it" answer.

Your useage dictates how many panels you should normally have installed.

Then of course, the smaller the trailer, the less panels you can install.

I hope this answers your question, and is not a case of "clear as mud".

Andy
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Old 02-11-2010, 10:39 AM   #4
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I'm interested in setting up a free-standing solar panel for the purpose of charging my batteries and keeping them topped off...
the details for this need have been dissected and posted many times,

so read a few of the solar threads with similar titles.
___________

now, ignoring ALL of that and all of the exceptions, issues, parts limitations and so on...

75-150 watts of collecting pv panels,

combined with a solar charger/controller and proper wiring will serve your purposes...


"topped off" is a confusing term and commonly misunderstood.

with the proper parts one can get the batteries up to 85-90% charge (given adequate sunlight)

but as the batteries approach this level...

the amount of time to get to 100% lengthens

and especially IF the batteries are in USE during the charging process.

IF the unit is NOT in use (stored for example) solar will eventually reach the 100% level for the batteries...

and then start to boil OFF water/over charge UNLESS designed to STOP charging at a given battery voltage.

the flooded lead-acid batteries on your unit will work fine with solar,

but will need maintenance and regular attention.

the gear needed to put this plan in play will run 1200-2000$

using reliable components and perhaps more installed.

otoh a 1000 or 2000 watt, quiet, small genset

can provide exactly the same function in LESS time and without regard for sunshine,

and ALSO provide 120v ac power when needed...

at a purchase price of 400-800$.
__________

again this entire issue (including solar vs genset) is EXTREMELY well covered in many archived threads....

cheers
2air'
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Old 02-12-2010, 12:00 PM   #5
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....
the gear needed to put this plan in play will run 1200-2000$ using reliable components and perhaps more installed. otoh a 1000 or 2000 watt, quiet, small genset can provide exactly the same function in LESS time and without regard for sunshine, and ALSO provide 120v ac power when needed... at a purchase price of 400-800$.
Honda gensets are $800 to $1000; they provide much more power, of course, but they do require gasoline and attention, and produce noise and smell. I'd definitely convert them to propane to avoid having to deal
with gas cans.

Solar power definitely requires moderation in power usage but the quiet is very nice.

- Bart
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Old 02-12-2010, 01:06 PM   #6
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Honda gensets are $800 to $1000...
not exactly.

i have 2x2000 hondas.

and stand by the 400-800$ price reference.

USED 1000s or 2000s are available for much less than the new BEST prices...

often the used ones are essentially UNused or with minimal hours.

even buying a 2000 NEW at 900-1000$ may ultimately only 'cost' 400-600$...

should one decide to SELL it after awhile.
___________

several members here have purchased slightly used 1000s or 2000s in exactly this way, from the common auction/sale sites.

no doubt one can also do a SOLAR set up for LESS than i've suggested above,

but portability and REsale may not be as good as a well cared for yam' or 'da...
________

the point being that it's less expensive to 'try' the generator approach when deciding which is the BEST match for needs...

running 1 'da for 2-3 hours every 3rd day is hardly much noise, smell or 'attention'...

and as suggested earlier ALL of these pros/cons/yesbutts/ohwait/minesbetter! issues are WELL COVERED in other threads...

so wind up a few electrons and read'em folks...
___________

btw my unit has both solar and genset power supplies.

cheers
2air'
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Old 02-12-2010, 02:11 PM   #7
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btw my unit has both solar and genset power supplies.

cheers
2air'

I expect to do the same eventually, but will be starting with a Honda 2k genset and an additional battery. Solar will come later as money allows.
Learning to reduce usage seems to be the first thing to do if you want to get the most for your dollars in a solar system.

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Old 02-12-2010, 03:13 PM   #8
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I read a report once by University of CA Berkley that stated Solar panels were at best 60% of the stated rating. Atmospheric conditions, wiring connections, wire size, battery condition, simple dirt on the panels, angle of panel to the sun. Doesn't make you think twice if you're wanting a solr array, just that you'll need twice as much.
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Old 02-12-2010, 03:39 PM   #9
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I read a report once by University of CA Berkley that stated Solar panels were at best 60% of the stated rating. Atmospheric conditions, wiring connections, wire size, battery condition, simple dirt on the panels, angle of panel to the sun. Doesn't make you think twice if you're wanting a solr array, just that you'll need twice as much.
Greg
The other thing they don't always tell you is that solar panels can put out MORE than the rated capacity depending on conditions. I think the 60% is probably based on how people have actually been using their panels, some of which were probably never cleaned or installed correctly, or adjusted to the sun angle correctly.
There is also a difference in the effectiveness of panels of different types. Thin film solar panels are better at producing power at low-light levels than rigid panels, but they lose effectiveness at high heat levels. Rigid panels are very effective in full sun, but cover 1/10th of that panel and you will produce almost nothing at all.

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Old 02-12-2010, 04:30 PM   #10
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That 60% is not far off with battery chemistry losses (~8 to 12%) tacked on - peak sunshine hours usually are defined as five hours straddling solar noon so anything weather-wise other than blue sky is where extra panels pay off. Sure Florida is the 'sunshine state' but that same peak solar makes those Caribbean rains that come every forty-five or ninety minutes just when you're counting on battery charging.

Too much solar is a good thing but then it needs to have a throttle. Having a charge controller that disconnects the solar from battery(s) when they've stopped accepting charge is a good thing for batteries but if you don't want to waste that power you have to use your batteries (go figure that one) OR have a controller that lifts the solar completely to switch it to another set of batteries or some other use.. .

Solar is a fickle thing - you need to find uses for it when the system is telling you excess is available, pump water, run fans, crank the stereo up, all the inverter things you'd never do in a three-day rain... (That's when generators rock!)

Pictured is a 285 watt panel weighing 105 pounds (tempered glass front and back) that was another deal too good to pass up just like the Parts'tream (another variety of Aluminitus, just one with deep blue high lights).
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Old 02-12-2010, 04:59 PM   #11
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Since I have the same size bambi as yours and our power usage sounds similar I thought I would share my practical experiences with solar. I purchased a single panel and controller from Costco (it's a Coleman and I think it puts out about 15 watts) a couple of years ago. We typically don't get out for more than 3 days at a time a couple of times a month, but I've been hauling the Honda with me every trip and never had to fire it up. I put the panel out first thing in the morning and by the end of the day the batteries are good to go. I did change out all the bulbs to led's and we are pretty conservative with our furnace usage during the winter, but the single panel has worked out well for us. It's funny how many folks walk by the campsite and comment-it boggles me how "novel" the concept still is to people.
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Old 02-12-2010, 11:44 PM   #12
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Pictured is a 285 watt panel weighing 105 pounds (tempered glass front and back) that was another deal too good to pass up just like the Parts'tream (another variety of Aluminitus, just one with deep blue high lights).
A group of twenty or so camped together at Burning Man one year using two 125 watt solar panels... we only ran short of power once, when some of the camp decided they were going to use the 1000W microwave to defrost all their food from rock solid frozen; we didn't have enough batteries to last. Otherwise, that was a smashing success as the two panels were much lighter than the generator and gas, and provided plenty of power for our LED lights, minor microwave use, black lights at night, etc.

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Old 02-13-2010, 01:27 PM   #13
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LED's

Quote:
Originally Posted by Johnco View Post
Since I have the same size bambi as yours and our power usage sounds similar I thought I would share my practical experiences with solar. I purchased a single panel and controller from Costco (it's a Coleman and I think it puts out about 15 watts) a couple of years ago...I did change out all the bulbs to led's and we are pretty conservative with our furnace usage during the winter, but the single panel has worked out well for us. It's funny how many folks walk by the campsite and comment-it boggles me how "novel" the concept still is to people.
Hmm. I like the idea of switching to LED's on the interior (and exterior, if possible). They are supposed to run at roughly 10% of the incandescent equivalent. In our case, that could offset $$ spent on a smaller solar setup. What LED source did you use?

-Jerry
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Old 02-13-2010, 02:45 PM   #14
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eleedz....

http://www.airforums.com/forums/f447...hts-17392.html

http://www.airforums.com/forums/f311...ons-27274.html
___________

and IF bambi only has 1 battery...

adding a 2nd 12v black box is the LEAST expensive way to gain juice...

1 deep cycle battery=<$ than 3-4 bulbs =<$ than genset <=$ than solar...

for boondocker lighting try candles !!!

no foolin thayz good!

cheers
2air'
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