Running a 12 Volt Frige on Solar Electricity

Discussion in 'Alternative Energy' started by Rick, Sep 8, 2006.

  1. Rick

    Rick Well-Known Member Supporter

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    Hi All

    Let me state from the beginning, that we will be buying new panels, and many deep cycle batteries in the near future.

    In the meantime, I have set our 4, 35 watt, 1970 vintage, Arco Solar Panels on the winshield and hood of our 1991 Honda Station Wagon. I ran the panels (wired paralel) into a Trace (Xantrex) Charge Controler, wth the voltage going into a CHEAP, 115 AH, 12 volt battery.

    The system works fine in full sun, and still left the battery at 12.37 when the sun was blocked by the clouds.

    The fridge does not list any thing re: 12 volt power use. I can give the following facts, however. The fridge took the battery from 12.25 volts (50 per-cent) to 11.87 volts on initilal connection. I expected that, and let the battery build for 5 hours in full sun yesterday.

    At that point, the battery held 13.6 volts. When I turned on the fridge, it took the battery down to 12.7 volts, and held this consistantly as the fridge continued to cool down.

    My questions are: if I buy 2 more of these 50 dollar batteries, and let them charge up, is there likely to be enough juice to make it through the 15 hour night? Are the 140 watts from the panels (total of 65 volts in full sun) going to be enough to keep the 3 batteries charged like they do the single battery?

    Thanks as always for any input!

    Rick
     
  2. wy_white_wolf

    wy_white_wolf Just howling at the moon

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    without knowing the wattage or amperage draw we really can't give an accurate answer. Can you get a watt meter and run it for a full day to get an idea how much it draws?
     

  3. patarini

    patarini Well-Known Member

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    If they are using one like we use in semis, about a 3 watt draw if i remember right!
     
  4. Fire-Man

    Fire-Man Well-Known Member Supporter

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    Hello Rick
    How are you getting 65 volts with the panels wired in parallel? Sounds like they are in series. Is your Charge Controller 12volts or 48, being you are getting 65 volts? Randy
     
  5. Rick

    Rick Well-Known Member Supporter

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    Mea culpa!


    The array is wired parallel - all positives joined and all negatives joined- I added their individual outputs (measured before joining them), which obviously confused things.

    I have a kil-a-watt ( 400 miles away), but I can't get my hands on it for 4 weeks. I didn't bring it because I did not think I could use it to measure appliances in a 12 volt system. Is there a way to adapt kil-a-watt's 110 input with 12 volt?

    It is a "Truckers" type fridge.

    It was partly cloudy today, and the battery voltage was dipping to 12.17 volts at times, so I set the charge controller to equalize my battery today, while I try to figure this out.

    Maybe someone can answer this- how far below 50 per-cent (12.25 volts) would you let the battery dip- would 12.0 volt lows with 12.6 or so volt peaks be safe for the battery?

    Thanks,

    Rick
     
  6. Jim-mi

    Jim-mi Well-Known Member

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    What type\kind of battery is it
    a 'car' bat ... ?

    At those low voltages your bat isn't gonna last long
     
  7. Fire-Man

    Fire-Man Well-Known Member Supporter

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    Rick, if you had a amp meter which is built into some of the multi meters, you can hook it in line with your fridge to see how many watts it is drawing(volts X amps= Watts) but to tell your system will keep a fridge running for 15 hours at night------can't answer that-------question-----Whats going to run the fridge in the day time? Another thing--don't spend your money on "Car Batteries"--------at least buy a deep cycle marine battery or two 6 volt golf cart batteries. You will not be able to convert a Kil-a-Watt to 12 volt. Make sure your panels are set "Right" with the Sun---Having the angle off will affect the output of your panels. Also if you were around alot--you could mount your panels to a piece of plywood--then set them on something like a small trailer and you can go to them several times a day and re-aline them with the sun(Manual Tracker--LOL)---it will help a fair amount with there output. Good Luck!! Randy
     
  8. Rick

    Rick Well-Known Member Supporter

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    The Battery is a low end, deep cycle battery with 115 AH capacity.



     
  9. Fire-Man

    Fire-Man Well-Known Member Supporter

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    Rick that should not hurt the battery!!

    To check amps with a Multi Meter that has a Amp (A) on it---First check the battery voltage while the fridge is running-(Example 12.6 volts)--write it down-------then turn the meter to A or Amps and make sure the wire leads are in the Right hole on your meter for checking amps---unhook the positive wire going to the fridge from the battery--hook the red lead from the multi meter to the battery---hook the black lead to the positive wire going to the fridge---making sure the fridge is running-----read the meter-----Example---if it was to read 2.65 amps---take the 2.65 amps X 12.6 volts==33.39 watts. I am not sure about a Gas fridge(12 volt) if the heating element stays on 24/7 or not--never checked into it------I run my Fridge on Gas

    Rick no one can answer that question because you don't know how many watts the fridge pulls.---Example---If your panels could give you 800 to 1000 "Usable" watts per day---and your fridge drawed 10 watts per hour(240 per day)---you will come out OK, but if the fridge draws 100 watts per hour(2400 per day) your systen will not handle it--------so if your fridge drawed no more than say 35 watts per hr-(840 per day) Your system would be maxed out, but if you had a cloudy day---your fridge is OFF. Hope this helps some!!! Good Luck. Randy
     
  10. Fire-Man

    Fire-Man Well-Known Member Supporter

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    Rick I don't know your set-up but if you have a vehicle that you drive a few miles a day-----you can always put a deep cycle battery on it-----without buying a isolator-you can fix it to where you can plug/unplug from your vehicle charging system and add a plug to the battery to plug in the 12 volt fridge----U could use this at night or when ever needed as a back-up. Good Luck!! Randy
     
  11. 12vman

    12vman Offgridkindaguy

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    I used a small fridge that was designed to be used in a semi that had a compressor for the freon. It drew about 4 amps while it was running. With 140 watts of panel, (knowing the fact that the "working" voltage is lower in older panels than the panels of today) on a good day, maybe you could collect 40/45 aHr. a day.. (at 12 V.D.C.)

    2 golf cart batteries would give you around 200 aHr. reserve. I wouldn't go much bigger on the battery than this. Just this amount would take 3-4 days to recharge them if you were to use them up..

    At this charge rate, I'd figure almost a 50% duty cycle. If you have a sunny location and the panels are installed properly, It would cover the fridge but not much more..
     
  12. Rick

    Rick Well-Known Member Supporter

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    Hey Gang

    I really appreciate the thoughts. I talked to a neighbor today who knows our actual solar panels, and that they ran a wringer washer, lights and a 12volt water pump. He thinks they could handle the fridge with 2 more batteries.

    I will use Fireman's instructions to measure the amps, determine the watts with the formula. My multimeter has "A" (over a line over 3 dashes) settings, and the instructions describe this as "current". The labels there are 200 with a funny symbol, 2m 20m and 200m.

    In case you need a laugh, I drove the solar Honda up our double switchback, to our homesite , to catch a few extra hours of sun.

    Stay well...

    Rick
     
  13. Jim-mi

    Jim-mi Well-Known Member

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    Adding 2 more batterys won't help if you can't even keep the one bat charged.
    Your "load" appears to be more than those pannels will produce.
    Time for more PV......