Forum Discussion

Slownsy's avatar
Slownsy
Explorer
Jan 08, 2015

Solar + batteris

We have a 30' titanium and wish to instal solar for dry camping and will likely hit a park once a week for dumping, fill up water and some laundry. It has a Inteli Power 4 operating modes 45A Pover converter . We live in Florida but intend to travel up to Canada and Alaska for summer. Fridge + HW will be on gas and we have an Atwood 15000 furnace which I believe draws 4.8-10.2A. Seiki SE20HSO4 led TV? and an Olivia 226 26" ? 2A, RCA DVD RTD3136EH ?A. and LED lights. Normally only use 2 at the time for say max 4 hours. I am considering instaling 2 140W panels, and have read that 24v cost less than 12v but then I have to buy more expensive controller ? I would prefer sealed batteries as access may not be easy but am also considering 6v golf cart batteries. Like to have display showing available amps, time, volts etc as well as what is going in from solar. ? What size controller, make of panels, batteries,controller recommended.

Thanks
Frank.
  • NinerBikes's avatar
    NinerBikes
    Explorer
    Jan 10, 2015
    Two 120 watt 12v panels wet up with PWM should get you 12-13 amps per hour at high noon for 2 to 4 hours daily, a bit less as the sun rises and sets.

    If you want to add a 3rd 120W panel at a later date, because 2 panels was not enough add another 6.5 to 7amps.... and a Solar 30 Charge controller has adjustable Vabs to 14.8V and will do the job.

    In starting the job, wire for at least 3 or 4 panels from the panels to the charge controller, gauge of wire wise.
  • BFL13's avatar
    BFL13
    Explorer II
    Jan 10, 2015
    I had a 230w and a 130w which was too much solar for our needs, so I sold the 130w. The 230w is just right. :) The 130w was not enough by itself though.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jan 10, 2015
    Hi Slownsy,

    A 400 watt inverter running flat out draws about 40 amps @ 12 volts. If it will be used several hours per day, I'd maximize the solar install if planning to not run a generator.

    Really an energy audit would be best. Even better would be actual amp-hours used. Perhaps the hardest thing about setting up a solar system is deciding on the number of watts.

    Mine was just fine when I was part time. Now that I'm full time, I wish I had 1000 watts. The only mistake I made was not allowing for expansion of the number of watts.

    I can say that nearly everyone loves what solar does for their camping experience.
  • Slownsy's avatar
    Slownsy
    Explorer
    Jan 10, 2015
    Thanks to the few who answered, we wil not be running microwave or coffe machines as the old gas kettle dos fine and already have 400w Inwerter from manufacture to entertainment area.
    Frank.
  • time2roll's avatar
    time2roll
    Nomad
    Jan 08, 2015
    Solar panels are a commodity item. If the wattage rating and physical dimensions fit your plan they are all about the same IMO. Actually if you will be going 12 volt and PWM controller it is best to compare Isc (short circuit amps) rating more than wattage. Best to have a controller rated at least 20% more than Isc. Find a local supplier to save shipping if you can.

    Sealed AGM is great but do cost more. There is no magic to have GC2 in AGM format as that is more of a wet cell advantage. If you go four batteries then 6v is much easier to assemble a balanced battery bank.

    I would go 3 to 4 panels (if they fit) if you do not have a generator. 2 panels is fine if you have a generator along.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jan 08, 2015
    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
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Jan 08, 2015
    Based on reports/recommendations here, I decided on two 140w poly's, in parallel, and a solar30 pwm controller. I should only need one panel in summer, but could easily use 3 in winter, so that could change. You'll have to consider when and where you plan to boondock.

    As for batteries, that depends on what appliances you plan to use. If no microwave, you would probably get by just fine with a pair of GC-2's, or equivalent AGM's. With microwave, I wouldn't go with anything less than 4 GC-2's, or equivalent. Furnace use will be a factor as well, as it is a relatively large draw.

    Then size your inverter accordingly.

    There is no shortage of meters available, in all price ranges. But no need to spend big on meters. Keep it simple, but get ones that display voltage to 2 decimal places for better accuracy.

    Ignore the prices from 2007, in the above link. I put my solar system together for about $500.

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