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D_E_Bishop's avatar
D_E_Bishop
Explorer
May 08, 2017

Comparing Solar Systems

I know this has been asked before! Yes I have found some great info in the archives, no I haven't found the answer I need.

My question is;

If currently we can go three days of dry camping(Hi Jolly for example) in the spring or fall, not needing to charge the batteries. Our rig is a 32 foot Adventurer with mostly LED lighting, most video stuff is 12vdc, TV is 120vac(requires using inverter), used maybe 2.5 hours if we watch a movie, normal draw for water heater and fridge and using a boombox on 12vdc maybe 2 to 3 hours a day instead of watching TV.

To extend our stay for a few more days, or indefinitely without using generator or engine to charge batteries, roughly what am I looking at adding. Of course I know there are tables to figure my average daily usage and I this is sort of cheating but would the general agreement be 2 GC2 batteries or will 4 batteries be absolutely necessary. How many panels totaling how many amps.

It is not going to be cheap to add two more batteries, the Adventurer is somewhat short on exterior storage and there is no room whatsoever in the understep battery compartment. While I have no problem installing the panels on the roof(there is a ton of info available from this site to help there) and wiring the new batteries if required or the panels and controller, I do not have the experience or equipment to weld together the steel to provide storage for the batteries.

This is my first foray into a real solar charge and maintenance system and I can do everything but the welding and it's not easy for me to sit down and fill out the estimating chart to determine what I will need. To be very clear it is a mental function I am not well equipped to do, I am severely dyslexic and get frustrated when faced with so many questions and need to remember things like how many hours a day we use appliances.

So if it is possible, how about some guesstimates to get me started on estimating costs, also what is a must read before I get too involved in this project.

TIA, d.e.bishop
  • D.E.Bishop , if I assume you have 2x6v already and you get em down to 50% in 3 days, that's about 30-40 amp hrs a day.

    daily irracianc multiplier for time of year/tilt/direction
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    I use "4" (spring/fall flat)

    40 ah/day / 4 (hrs/day!) = 10 amp panel. 10A * 18v = 180 watts of solar to extend, double or triple for full time!
  • If you then need to add batteries and welding plan it out. Cut the metal etc and screw it in place as needed for the new batteries - ie use sheet metal screws etc. Then go to a welding shop and it will be minimum cost as there is no setup. You may need to first cut out prior battery supports.

    You will need to completely disconnect ALL batteries and solar before welding.

    BTW Label and take pictures of all wiring before anything else.
  • I just put in 3x160w panels and 2 additional batteries totaling 4x12v and a 2000w inverter so I can work full time from the RV. I left my go-power 30amp power controller and now regret not switching it out for MPPT. Once I upgrade to a MPPT I'll be set.
  • 3 days is good and to extend that just add solar. I'd guess about 300W but allow for additions. Battery life and AHs can be improved with GC2s but it doesn't seem like you need them.

    If you really want to get a handle on battery usage then install a battery monitor like the Trimetric. You'll then know your usage, battery charge state etc. This is an invaluable device for dry camping.
  • 3 days is good and to extend that just add solar. I'd guess about 300W but allow for additions. Battery life and AHs can be improved with GC2s but it doesn't seem like you need them.

    If you really want to get a handle on battery usage then install a battery monitor like the Trimetric. You'll then know your usage, battery charge state etc. This is an invaluable device for dry camping.
  • Please clarify the three day limit now--is that when, even with the solar on nice days, your battery runs down as far as you want to let it get down to?

    -double the battery bank and keep the same solar, add some solar, or do both.

    Or, is that because in Spring and Fall it hardly ever goes more than three days of nice days for solar, and the battery runs down in cloudy conditions?

    -more solar won't help much if any when solar conditions are poor. Add battery and run the gen to power the battery charger until the sun comes out.
  • I started with two 6 volt batteries, two 160 watt solar panels, MPPT controller, and a 150 watt inverter for the TV. This worked great for us. After a couple years I did upgrade to four batteries, three 160 watt panels and a 2,000 watt PSW inverter.

    Build a system that you can add onto, then you can add more batteries and panels if you need to.

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