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Connect BOTH 12v appliance and 110v inverter to battery?

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  • Connect BOTH 12v appliance and 110v inverter to battery?

    Can I connect a 12v portable fridge AND an inverter to my battery bank? I would like to lower energy required to run a 12v fridge (versus 110v minifridges) and have an inverter to power everything else (all 110v)? Both the inverter and fridge would need to be connected full-time.

  • #2
    Originally posted by amybluekat View Post
    Can I connect a 12v portable fridge AND an inverter to my battery bank? I would like to lower energy required to run a 12v fridge (versus 110v minifridges) and have an inverter to power everything else (all 110v)? Both the inverter and fridge would need to be connected full-time.
    The AC/DC fridges have the capability of running directly off of DC (Engel, ARB, Whytner, Dometic, etc) and some of them have built in Low Voltage cutoff. However you will pay a premium for these appliances. There are energy efficient (Energy Star) AC refrigerators for much less, and so if you want to do this to save money you will need to factor in the premium cost of the fridge.

    I don't know of any reason not to hook up the fridge and inverter at the same time, however in reading the user manual for one of the portable fridges it warned against charging the battery with a higher voltage while the fridge was connected.

    I don't understand this, so I would like to know if anyone else has heard of this, because it seemed to me that the DC input range was wider than what a battery charger would put out voltage wise.

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    • #3
      You can connect both - no problem.

      Inverters are covered more in depth elsewhere, so be sure to see if a Pure-Sine-Wave model is better for your needs than the cheaper, and less flexible modified-square-wave types.

      Comment


      • #4
        Connecting both is fine, as long as you don't overly deplete your battery.

        The other question is , will your 12V fridge like the 15V charging voltage the battery should charge at ?
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          Mike is quite right - full time might be an issue if the inverters can't handle what is typically the absorb voltage. I've seen some rated at 16v max, but best to check.

          The other issue is just that - with active loads on the battery, the controller may stay in an endless absorb - forcing you to lower the charge voltage on your bank to say only 13.8 float with no absorb at all to protect the battery..

          Comment


          • #6
            Originally posted by Mike90250 View Post
            Connecting both is fine, as long as you don't overly deplete your battery.

            The other question is , will your 12V fridge like the 15V charging voltage the battery should charge at ?
            I found what I had remembered in the Engel and ARB manuals. Would you consider a three-stage charger to be a high speed charger? What about equalization? The other thing I was wondering is that when a battery is being charged, does the voltage from a charger get passed directly through to the fridge since they are basically both directly connected to the same place?

            ###
            Engel User Manual
            http://www.google.com/url?sa=t&rct=j...LGHIj9BQyxp-1A

            Engel
            QUICK CHARGING THE BATTERY.
            Never hook the freezer up to a battery charger directly. It must only be attached to a
            battery.

            Note: Also says to only use inverter generators or generators with over voltage protection.


            ARB
            Disconnect the fridge freezer from the battery before using a high-speed battery charger.

            ARB User Manual
            http://www.google.com/url?sa=t&rct=j...F3g86TFFN7K77Q

            Comment


            • #7
              High speed chargers are the ones mounted on a wheeled cart, that car dealers use to start cars on the lot. They pump 20 or 30 volts at couple hundred amps into a battery for a minute or two, to get the car to start

              3 stage chargers are not high speed chargers, they have a very controlled voltage output. Speed depends on how many PV panels you have, a 2Kw array will charge faster then a 1Kw array. But with solar, we are talking bulk and absorb times of 3 to 6 hours. Not fast at all.

              What is your array size and model of charge controller ?
              Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
              || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
              || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

              solar: http://tinyurl.com/LMR-Solar
              gen: http://tinyurl.com/LMR-Lister

              Comment


              • #8
                Originally posted by Mike90250 View Post
                High speed chargers are the ones mounted on a wheeled cart, that car dealers use to start cars on the lot. They pump 20 or 30 volts at couple hundred amps into a battery for a minute or two, to get the car to start

                3 stage chargers are not high speed chargers, they have a very controlled voltage output. Speed depends on how many PV panels you have, a 2Kw array will charge faster then a 1Kw array. But with solar, we are talking bulk and absorb times of 3 to 6 hours. Not fast at all.

                What is your array size and model of charge controller ?
                I don't have any solar yet and if I do it will be emergency backup only. I was thinking of a dc portable fridge with low power consumption but am now rethinking it due to the high price and no immediate need. My primary backup will be with an inverter generator through a manual transfer switch.

                Comment


                • #9
                  Originally posted by lkruper View Post
                  I don't have any solar yet and if I do it will be emergency backup only. I was thinking of a dc portable fridge with low power consumption but am now rethinking it due to the high price and no immediate need. My primary backup will be with an inverter generator through a manual transfer switch.
                  +1.

                  IMO solar generated power has it's place and importance. But for some there are other more financially justified options to consider for an emergency power spurce.

                  Comment

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