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wademartin's avatar
wademartin
Explorer
Jan 23, 2015

Solar system advise needed

I want to install a solar system in my 28 foot Gulfstream Innsbruck 5th wheel camper. I will be operating the furnace, hot water heater, stove and refrigerator on LP gas. I need to install an inverter to keep batteries charged and to operate a TV, satellite receiver, radio, and computer. Suggestions on what size solar panels , roof mounted or portable, what size inverter, and battery bank will be appreciated.
Thanks
  • You could get by on two batteries if the sun is good every day or you have a small generator to use if needed. Otherwise with a few cloudy days and no generator I recommend 4x GC2 (golf car batteries).

    Again 200 watts solar will work great when conditions are good. 300 to 400 watts would serve better when the sun breaks out after a few bad solar days.

    Solar controller keeps the battery charged. Inverter will supply 120vac from the battery. I have and recommend the Go Power 300 watt sine wave inverter for the usage posted. Very low idle current and has a provision for a remote power switch.

    Price and compare 12v panels at the Isc rating (short circuit amps) not wattage. High voltage (24+v) panels are lower cost, physically larger, and require a higher cost MPPT controller. Make sure the panels will fit properly with 12 to 18" spacing away from shade items like air conditioner, open vents and antenna. Even small partial shading can cut power significantly.

    > Forum Members Solar Installations With Pics
  • Depending on outside temps, the furnace can pull 40-60 amp hours a day (with snow everywhere). Where you are going to winter is an important variable in this equation. Will you ever have hookups, how often. Batteries can be short cycled (not charged to 100%) a few times, but it doesn't take long to damage them (10-15 cycles).
    The TV and computer are going to be expensive loads (power demand wise).
  • You could probably run the 120 volt items listed on a 300 watt pure sine wave inverter.

    The battery bank size would be determined by the total run time of the items using 100 watt = ten amps per hour of use.

    For example, if the computer draws 80 watts and is used for 8 hours, it would use 640 watts and require 64 amp-hours. Since even deep cycle batteries need to be kept above 50% the battery requirement for that one item is 128 amp-hours.

    Here is a simple flow chart.

    Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

    One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher 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