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RVing message boards => Tech Talk => Solar => Topic started by: soaringchicken on May 19, 2010, 03:09:33 PM

Title: What type of solar panel should I buy?
Post by: soaringchicken on May 19, 2010, 03:09:33 PM
Hello all.  I recently purchased a 1985 20foot Toyota Dolphin at an amazing price.  I fell in love with it because of its relatively great fuel economy.  I am an artist and will probably be wanting to power computers, lights, and other electronics more than the average camper so I figured I would invest in a solar panel.

Does anyone have any suggestions?  What is a good wattage?  I understand there are panels for powering your life, and then there are panels for charging your battery.  I really have know idea what wattage is good for what, what kind of panels to buy and what they may cost.  I am a bit of a penny pincher so I'm not going to seriously look into panels costing a couple grand.

Thanks a million.
Title: Re: What type of solar panel should I buy?
Post by: DesertDew on May 20, 2010, 05:11:13 PM
A friend of mine has a '79 toyota 20' MH.  They run forever.  Until someone chimes in with helpful info, you might check out this old thread and others: http://www.rvforum.net/SMF_forum/index.php?topic=7626.0.  I've been checking into panel needs, too.  I believe I'd need quite a few for my needs. 

As for thriftyness, solar panels are easy & inexpensive to make for the DIY'er.  A relative of mine made a large bank of them to heat the pool.  Lots of instructional videos on youtube.  (I also use hoses coiled up on the rv roof for hot water, along with a $4 diy solar oven to cook many meals with.  Was gonna make roasted chicken & veggies for dinner today but ran out of oven bags, lol.)

Still trying to find a link for you with lots of good info...have it here somewhere... 

Good luck! 
Title: Re: What type of solar panel should I buy?
Post by: Pubtym on May 20, 2010, 08:23:07 PM
Hello all.  I recently purchased a 1985 20foot Toyota Dolphin at an amazing price.  I fell in love with it because of its relatively great fuel economy.  I am an artist and will probably be wanting to power computers, lights, and other electronics more than the average camper so I figured I would invest in a solar panel.

Does anyone have any suggestions?  What is a good wattage?  I understand there are panels for powering your life, and then there are panels for charging your battery.  I really have know idea what wattage is good for what, what kind of panels to buy and what they may cost.  I am a bit of a penny pincher so I'm not going to seriously look into panels costing a couple grand.

Thanks a million.

Step one is identifying the types of things you would like to power how many times a day with this supplemental energy provider..as you boon dock.

Step Two is adding up the total AC wattage required of each item for that day. That's the desired power generation needed to store in a battery...for a suitable inverter to power the items.

Step Three is to find a solar panel capable of generating that wattage during a 4-5 hour sun day..

As a penny pincher..you'll now stop dead on this idea. :o

Title: Re: What type of solar panel should I buy?
Post by: tennsmith on May 21, 2010, 10:25:45 AM
Solar panels are relatively expensive if you buy an "already built" unit.  Harbor Freight sells a set of 3 panels producing 45 watts for about 200 dollars.  45 watts won't do a lot.  They would run your laptop for a while.  You could opt for LED lighting as opposed to standard 12vdc lights and that would be a big help, but that too does not come cheaply.  LED bulbs average several dollars each.

Most folks on this forum who are solar advocates/users and claim to get benefit from them have 200-300 watts worth of arrays.  As Desert Dew says, you can build your own arrays cheaper than you can buy them, but I'm thinking that by the time you buy all the cells and the materials to build frames and the charge regulator required to manage the output, you're still gonna be out 1000+, not to mention your labor, for a decent setup and your frames are likely to be heavier and bulkier than the pre-made units.

Real estate upon which to mount them on a 20' RV is going to be at a premium.  In short, watts=square footage so the more watts you want/need, the more square feet of array you'll require.  More wattage generated by more array area means more "storage" capacity and that means batteries.  It does no good to have 300 watts worth of solar array if you have only a single battery.  300 watts of array in sunshine for 8 hr, generates 2400kwh and that means 200 amp-hr of charge capability for a 12v battery.  Most 12v units are rated at 75-80 amp-hr, so 3 would be required just to store the available charge if they were completely flat and the plot thickens if you obey the "do not discharge past 50% of capacity" rule of thumb for extended battery life.  That, then doubles your battery requirement to 6.

All of this predicated on the assumption that you wish to use your electrical goodies at night as well as in the daytime.  If you would be a daytime only user, then all you really need is enough array wattage to offset the wattage requirements of your toys.  Most folks use lights, TV, etc at night so you must "replace" that energy the next day as well as what you use during the daytime.  Perhaps a small inverter type of generator would make more sense.  They are quiet and extremely portable and can be found used, sometimes, for a significant savings over retail.
Title: Re: What type of solar panel should I buy?
Post by: Mc2guy on May 21, 2010, 10:40:12 AM
  300 watts of array in sunshine for 8 hr, generates 2400kwh and that means 200 amp-hr of charge capability for a 12v battery.

I think you meant 2400 Wh, or 2.4 kWh. :P 
Title: Re: What type of solar panel should I buy?
Post by: tennsmith on May 21, 2010, 11:35:58 AM
My bad Mc2guy, you are correct :-[
Title: Re: What type of solar panel should I buy?
Post by: RVRoadTrip on May 21, 2010, 01:07:01 PM
The Kyocera KD135GX-LPU 135-watt panels are smaller than most and may be a good fit for you.  These are the panels we bought for our 19' travel trailer.  AMsolar also sells skinny panels and they are good quality as well. If you can fit Evergreen panels, they are the best bang for the buck but they tend to be big.  Don't waste your money buying solar from Harbor Freight and expecting it to do what a well planned system will do.
Title: Re: What type of solar panel should I buy?
Post by: Pubtym on May 23, 2010, 05:58:56 PM
http://www.altestore.com/howto/Solar-Power-Residential-Mobile-PV/Mobile-Power-Systems/Renewable-Energy-System-in-Your-RV-or-Boat/a69/
Title: Re: What type of solar panel should I buy?
Post by: Pubtym on May 23, 2010, 06:10:39 PM
http://www.hurricanewindpower.com/servlet/the-168/Hurricane-wind-turbine-wind/Detail

Mount on a 20- 30 footpole fastened to your rear hitch..they make them..
Title: Re: What type of solar panel should I buy?
Post by: Pubtym on May 23, 2010, 06:29:41 PM
http://www.tangarie.com/files/specs/Master_GALE%20_1_08_24_09.pdf
Title: Re: What type of solar panel should I buy?
Post by: PJ Stough on May 23, 2010, 07:26:22 PM
Before buying anything solar, here is a good link for general information:

http://handybobsolar.wordpress.com/2009/07/22/solar-power-that-works/ (http://handybobsolar.wordpress.com/2009/07/22/solar-power-that-works/)

Here is where I have found the best prices on panels.

http://sunelec.com/ (http://sunelec.com/)

Hope this helps some.

Paul

Title: Re: What type of solar panel should I buy?
Post by: RVRoadTrip on May 27, 2010, 10:32:12 AM
HandyBob is not accurate on several issues he talks about.  His page is more of a rant than a helpful guide. For example, his stance on MPPT charge controllers is just ridiculous.  He plainly does not understand the technology and what they do (they convert excess voltage into amps, among other things).
Title: Re: What type of solar panel should I buy?
Post by: Pubtym on May 27, 2010, 09:34:28 PM
http://www.solarpanelstore.com/solar-power-packages.cse-rv-systems.rv-upgrade-series.130w-rv-kit.info.1.html
Title: Re: What type of solar panel should I buy?
Post by: soaringchicken on June 29, 2010, 09:34:45 PM
Wow I just noticed all the replies!  Thank you so much for all your help! I will look into all these options and get back you you guys.

Thanks again
Title: Re: What type of solar panel should I buy?
Post by: Sarguy on June 30, 2010, 12:27:13 PM
Any suggestions for a small panel that would keep a pair of batteries trickle charged when RV is stored?
Title: Re: What type of solar panel should I buy?
Post by: Tony_Alberta on June 30, 2010, 03:44:32 PM
Real estate upon which to mount them on a 20' RV is going to be at a premium. 
Not that it's likely to be terribly practical unless you had lots of storage room but I was thinking about the "lazy susan" concept for mounting the solar panels rather than flat on the roof.  Build some kind of easy to assemble frame with the solar panels mounted at an appropriate winter angle for your latitude.  Then put the frame on some kind of legs and a horizontal bearing so the panels can swivel.   Kinda like an office chair without the wheels and without the chair.

At night face it eastish.  A bit before noon point it south.  At 3 pm point it to the westish.

But I doubt this is very practical.