Solar power for travel trailer...low bucks

[krieger]

Does anyone out there have any ideas/sources for adding solar to a travel trailer? It seems to me ya gotta give an arm and a leg to do this. I have a decent understanding of the workings of solar and currently would like to keep a set of 6 volt golfcart batteries, in series, at full charge. We "dry camp" and often must bring a generator to charge up the batteries. I run very little on an inverter, nearly nothing, but running the heat, 12 v, discharges the batteries in a night or two.

Any ideas would be greatly appreciated!

TIA
Michael

[admin]

This might get you started:

Add solar power to your truck camper By Jeff Yago http://www.backwoodshome.com/articles2/yago93.html

You'll find lots of other solar-related articles online. Near the top of the navigation column to the left, click on Article Index, then Energy.

Good luck with the project. Please keep folks here apprised of your progress with it.


Oliver

[SolarGary]

Hi,
Some of the articles here:
http://www.builditsolar.com/Projects/PV/pv.htm#Small%20Systems

on small systems deal with trailer and cabin systems, and may be of help. The last one is a pretty good treatment of RV 12 volt systems with solar.

Some places sell RV size systems are fairly reasonalble prices -- we got one from Costco that might work for a trailer -- if you search www.costco.com for "solar" a couple come up.

Gary

[JAK]

A system for a small RV is an interesting problem, depending on how often you use the RV, and how long you camp in one place when you do. If you use solar power at home, then you can better justify having solar panels on the RV and use them for the home when you are home. If your RV is you home, same difference.

If you are on grid and don't use solar power at home, then the backup generator for your home might be the answer. In addition to this, you might rig up an efficient system for recharging while going down the highway, either off the alternator, or perhaps a small DC generator running off the trailer axle.

The other part of the equation is how many batteries to haul around, and what type. Again, if you are off grid at home then they can be tied into the home when you are there. If you are on the grid and the batteries are only for travel and blackouts, then you don't want to spend too much on them. But you do want to have enough so that they charge and discharge more efficiently. You also want to minimize the charging rate and the discharge rate and the total energy used.

To reduce the charging rate, one of those 1000w honda generator might be the answer, or a small solar panel for trickle charging. To reduce discharge rates run your main loads while you are charging, and spread out the loads over time. I wouldn't use the electricity for any heaters. For the fridge I would get a good sized one and fill it half full of ice and have it well insulated. Then you could leave it turned off except when charging while traveling down the road, or off the solar panels, or off the generator. The ice would act as your energy storage for the fridge, so you would never have to run the fridge off the batteries. Just some thoughts.

I don't know if there is a practical way to run hot water back to a small trailer from a radiator when on the road. You probably don't want to mess with the exhaust. Also some sort of batch solar water heater might make sense for showers. A Kelly Kettle is an excellent water heater for making coffee and hot meals and washing dishes. The large one might be big enough for topping up your shower water. Anyhow, these sorts of primitive systems would greatly reduce your DC power requirements, and batteries and generators and all the rest.

http://www.kellykettle.com/products.html

[torenghout]

unisolar panels are light weight and bullet proof.

[Phssthpok]

unisolar panels are light weight and bullet proof.


Werd.

I accidentally ran over one of my US64's (don't ask) and it still puts out full power.

As for sourcing PV on the cheap, I check Craigslist every day. Maybe once every two months I'll see an ad for used panels. It's taken about a year and a half but I've built up over 1Kw of panels SOLELY off of Craigslist.

[ryanmercer]

unisolar panels are light weight and bullet proof.

Wish I had 8k$, I'd buy a pallet of 25 of the 64W's

8,070.00 for two us 64's, google "unisoler panels" and it's on the froogle links that pop up. :)

[12vman]

http://store.altenergystore.com/Solar-Electric-Panels/51-to-99-Watt-Solar-Panels/UniSolar-64W-Solar-Panels-PALLET-25-panels/p4408/?source=froogle

$5.00/watt.. That's about the going price. You would save on the shipping though.. ;)

I would agree with using Unisolar panels. Lightweight, No glass to worry about, Flexible.. (Even the solid framed units to a small degree)

The only disadvantage is that they are a little larger in size per watt compared to other types..

The thing to remember.. By adding a P.V. system to your travel trailer would be an investment that will last for years if installed properly. Most panels have a 20+ year warranty. You could wear out a few generators in that time period and you don't need to change oil or feed them fuel to make them work. (Not to mention the noise issues)
For the price of fuel by operating a generator for a couple of seasons, You could replace the batteries.. (Which can last 4-5 years if maintained properly)

The initial investment is somewhat high but it will pay off in the long term..

Low Bucks.. Forget it! Buy quality equipment! You won't be sorry in 5 years.. Believe me..

Food for thought..
You only have so much room to mount panels on your roof. This will limit your amount of wattage. Carefully measure the amount of possible mounting area compared to the sizes of the type of panels you choose to purchase. After you have an idea of the maximum amount that you can mount, Purchase a charge controller that will handle that amount. This will avoid you from making a major wiring change later down the road if you decide to expand..

Charge controllers are much cheaper than panels and having to deal with rewiring headaches. Select the right one from the start. Install a central wiring "Buss" on the roof or near the panels outside to connect the panels to the controller that will be inside. Once this is done, Now you can add panels over time without doing any major changes or change out the controller for that matter. It's already in there! Adding batteries is fairly easy..
~Don

[Backwoods_Bob]

krieger,
I'd try one of these 200 dollar kits form Harbor Freight -
http://www.harborfreight.com/cpi/photos/90500-90599/90599.gif
45 watts of panels, charge controller, two lights and some wiring - You already have the batteries and inverter. You'd be all set!

[jen_in_southtexas]

what can 45watts power?

[12vman]

During prime conditions, (full sunlight) 45 watts of panel will give you around 3.75 amps of charge @12v.d.c. Not alot straight from the panel but if saved in a battery and used at a low rate, it could last all night.. (depending on the loads)

I use a simple formula that works for me.. ;)

During the day there's a "prime time" charge period "window" between the hours of 10 a.m. and 2 p.m. with the panels pointed solar south and at the correct angle towards the sun. (per area) check the winter angle (http://www.macslab.com/optsolar.html)

I figure the amount of amp hours that can be collected is within this "window" of time. Of course you will collect a little before and after these times but this will usually cover the normal losses within the battery while charging. (around 20%)

In your situation, with 45 watts of panel as an example, multiply the charge amount possible with good, sunny conditions (3.75 amps) by the "window" charge time which is 4 hours. This will give you around 15 amp hours that can be saved into a battery. *Less during cloudy conditions*. Never forget that!..

Your goal is to stay within or under this 15 amp hour level as for loads in a 24 hour period. This will depend on the items that you operate and the amount of current that they draw. As an example, my laptop computer draws around 5 amps. I would only be able to use it on this 45 watt system for around 3 hours and that would be pushing things to the limit. *You never want to use (in a 24 hr. period) more than what can be replaced in a days worth of charge*. Now you can see why it's important to keep an eye on the amount of stuff you use and the amount of power that they consume..

Don't forget the battery.. How big..?

With the above amount of panel, I would figure around a 60 amp hour battery. You should only draw a battery down to around 20-25% maximum. Being that you can replace around 15 amp hours on a good day, multiply that by 4 to get an estimate on battery sizing. Now if you stay within the 15 amp hour limit of usage per day, you will only draw the battery down to the 20-25% level which is safe.. Make sense? ;D
~Don