Solar System Purchase for Weekend Boondocking

Looking for some advice on our upcomming purchase of a DIY 12v Solar System. We've done lot's of research and we are on a small budget. Our frequent trips are usually 2-4 days at a time. We really only NEED to run the water pump, propane detector and a few lights. This totals 6-7 Amp Hours / Day using online usage calculators = super low usage.

Here is the 100W Solar Panel we've decided on. $169 & free shipping:

http://www.amazon.com/RENOGY-Monocrystalline-Photovoltaic-Battery-Charging/dp/B009Z6CW7O/ref=sr_1_1?ie=UTF8&qid=1387034158&sr=8-1&keywords=100w+solar+panel

The Converter in our travel trailer does not work. So rather than replacing it we are going solar. We almost never hook onto Shore Power (dedicated boondockers). So, when we install our little solar system, what will we lose by not having the converter? and will there be wiring problems created by the not-working converter/charger?

Charge Controller: We'll get the best PWM w LCD that we can afford. MPPT is just too expensive:

http://www.amazon.com/Amp-PWM-Charge-Controller-Display/dp/B00FB3OPKM/ref=sr_1_2?ie=UTF8&qid=1387034226&sr=8-2&keywords=30a+charge+controller+with+lcd

We currently have a typical cheapo 35 Amp Hour battery. Could this setup handle:
1. A second battery?
2. A second panel?
3. A real battery with 70-80 Amp Hours?

When finances allow, we would like to expand our system. So overall, would this be a worthy start? How would you expand later? Maybe different start up purchases?? Maybe sell all this and start again with a real MPPT charge controller???

We are soon to take the leap into this little PV solar system setup for $270-$300 and use last years battery. Then a new battery ... then 2 batteries ... and then... and then... EEEK!

And finally, will this small system require a FUSE and/or a KILL switch? Each time you cut and connect wire, you lose some valuable power. But what level of saftey is neccessary?

THANKS !!!

Oasisbob
Explorer
Dec 14, 2013
Based on your estimated duration and power consumption I really do not see a need. We can do four days easy with out twin group 27 deep cycles and three of thise nights we watch a bideo on our 19 inch flat screen. We may charge batteries with a small Honda EU 1000 if we stay more than four days.Merry Christmas and good luck
wbwood
Explorer
Dec 14, 2013
We have two group 27's and we did a weekend trip. We have two fantastic fans that we would run at night. Watched about 1-2 hrs tv. Lights were led and we used them very little. Of course we used the water pump. I was uncomfortable with the battery levels the next morning, so I ran the generator for about an hour. I was afraid of it getting down to 50%. Never did but it was in the back of my mind.

With that said, I think it's a great idea to have the solar to help out some. Especially in Arizona.
2oldman
Explorer II
Dec 14, 2013
Oasisbob wrote:
Based on your estimated duration and power consumption I really do not see a need.
Me neither. Perhaps carry another charged battery along.
westend
Explorer
Dec 14, 2013
I guess if his converter isn't working, he needs some manner of charging the battery or did I miss something?

Here's what I'd suggest: Upgrade your batteries, I didn't know a 35 AH battery is even made. Your usage is lowballed, but I would plan ahead to installing 200AH, at a minimum. Current prices on modules for your anticipated use indicate it would be centered around 100-130w modules. Buy a name brand charge controller, the few dollars saved by buying a cheap controller is a false economy. Install everything with wire size larger than just adequate. Carry, at a minimum, a battery charger to recharge your batteries in exceptional situations and to equalize them at intervals. A good three/four stage converter is a better choice, IMO. Solar will do a great job with your batteries but you need the Plan B of a charger to be safe and secure.

One thing not mentioned is the eventual increased use of power once you have solar. I think you'll find that you will be powering other devices that were prohibitive with your old system.

Look around for deals or sales on the bits and pieces of your new solar system. I have had good luck with Solar Blvd..
2oldman
Explorer II
Dec 14, 2013
westend wrote:
I guess if his converter isn't working, he needs some manner of charging the battery or did I miss something?
You may have missed how little power he uses and how short his trips are.
gwilheln
Explorer
Dec 14, 2013
I have a 125watt sistem on are 5th wheall it dose very good keeping the batterys up in good wether. I all so have a 19ft. that has soler on it dont have all the electronic stuff. It hasnt bene on shore porer in the last 5 or 6 year up hear in idaho jest keep snow off.
2oldman
Explorer II
Dec 14, 2013
LOL^^^^
rexlion
Explorer
Dec 14, 2013
You almost could get by one one fully charged battery, with no way to recharge during the trip, for your entire 3-4 days at 7aH/day. But that would drain the battery too low, not a good thing. You can get a second battery, or get a solar setup... either one would get you though the trip.

I have a group 24 battery, and last spring I added a 75W panel and a Morningstar SG-4 pwm controller, all for about $125. I wired my controller to my panel with a chopped extension cord; that way I can plug in more extension cords as desired to extend the panel to unshaded areas. I camped without hookups for a week in Yosemite and never ran short of power.

The panel you like should work fine for you. Lights on the controller could be nice, but you can just as easily check your battery with a voltage meter. Add some alligator clips or something to connect to your battery terminals, and you're set.
AlbertaNewbie
Explorer
Dec 14, 2013
I would get a 100watt panel and a blue sky pwm controller. it will need a 15 amp fuse nearest the batt on the positive lead. should be able to do this for around $300.
pianotuna
Nomad III
Dec 15, 2013
Hi,

I think you are low balling your usage.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the high the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link: Golden rules of solar