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12 Volt inverter question

Discussion in 'Survival (Preps & Homestead)' started by southfork, Sep 7, 2017.



  1. southfork

    southfork Mother Lode Found Mother Lode

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    I have a 12volt inverter, want to hook up 2 batteries in parallel one will be the car battery and im running wire from car battery to another batttery and that will be hooked up to the inverter, its a 2000 watt 4k peak unit, will #3 wire be sufficient or do i need larger? Im only going to be running a refrigerator on it and a led light
     
  2. bb28

    bb28 Silver Member Silver Miner

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    Alton and mayhem like this.
  3. southfork

    southfork Mother Lode Found Mother Lode

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    Drop not the issue, only going to be 8 foot of wire between batteries and inverter.


     
  4. southfork

    southfork Mother Lode Found Mother Lode

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  5. Someone_else

    Someone_else Gold Member Gold Chaser

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    Your wire should be fine. Some years ago, I measured my kitchen fridge, used all the time, and a medium sized fridge. The main fridge averaged 100 watts and the smaller one 33 watts. They will draw more, of course, when the motor starts, but that's not a problem. If I were doing this, I would consider #6 wire, put on a 50 amp fuse and call it good. Or use your #3 in case you want more current later.
     
  6. Howdy

    Howdy Silver Member Silver Miner

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    When you run batteries in parallel, they should be as close to identical as possible. You can run mismatched batteries for a while, but one will overcharge. Two batteries may not be enough to run a fridge.
     
  7. bb28

    bb28 Silver Member Silver Miner

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    It depends on the type of fridge. Is it a dorm type fridge? Massive fridge? Energy efficient?

    I can't see needing a 3 gauge just to connect batteries to the inverter. That seems rather extreme.

    bb
     
  8. ttazzman

    ttazzman Midas Member Midas Member Site Supporter

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    Based on Inverter full capacity
    Input --2000w / 12v =167amps.......4000w = 334amps
    wire size
    1/0 = 170amps copper
    350=350amps copper

    this is why you dont sit and keep cranking a starter motor on a car....for bigger continuous loads its better to move up to a higher input voltage inverter a unknown here is the efficiency rating of the inverter also

    of course those are max continuous loads...makes it obvious real quick how important it is to know the actual wattage of the appliance your wanting to run

    also understand most 120v household outlets are 15amp x 120v =1800watts

    Based on a guessed load only capacity
    generator sizing charts show a energy star unit to require on average 1200 starting watts and 200 continuous running watts....1200watts/12v =100 amps starting load...based on that you could standard battery cable use 6ga up to 5'...4ga up to 9'...2ga up to 14ft (you can google "Battery Cable Amperage Capacity Chart" ) to get battery cable ratings......this would allow you to run your unit but not run full inverter capacity all the time

    a person needs to get a understanding of the battery amp hour capacity also in sizing battery's not all 12v battery's are created equal (another discussion)(i estimate for 200w continueous running for 24hrs you will require appox a battery rated for 90ah (amp hrs))

    THE ABOVE IS ESTIMATES MADE ON SPECIFIC ASSUMPTIONS


    wire-size-chart.jpg
     
    Last edited: Sep 8, 2017
  9. Buck

    Buck Gold Member Gold Chaser

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    Use a good set of jumper cables
    When you discover you either don't want to continue with your project or it doesn't work and needs more something, let's say batteries, and you don't want to drop any more money, you'll have a great set of usable jumper cables or, cut the ends off and stuff the copper into terminals and go that method, either way, you'll have a good set of 4 gauge cables doing the job, just fine but when the motor on the fridge fails to fully start and starts rattling like it's going to rip the rubber mounts apart, turn the fridge off until the batteries are fully charged.
    You don't want to break the motor or the mounts
     
  10. Howdy

    Howdy Silver Member Silver Miner

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    Very good point! Manufacturers have been known to exaggerate the numbers to edge the competition.
     

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