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Cheap watt meters & high constant loads?

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  • Cheap watt meters & high constant loads?

    I have two of these watt meters attached to my portable battery for input (solar & charger) & output to just know how many AH I use & put back in. At the time they were cheap & easy to use & I was only running a few fridges & LEDS.
    Now I have beefed up the solar to 500watts which is around 40amps, plus I now have an inverter using up to 30+amps.

    There does not seem to be any clear answer on how much these things can handle in the instructions, mine seems to say it can handle 75A continuous. The small cables are 12Ga wire.

    So can anyone say what the safe continuous amp rating on these things would be? Would they drop the voltage too much?

  • #2
    To handle 75amps continuously you really need wires & insulation sized to handle more than that. If the wires that are connected to that meter are really #12 AWG I seriously doubt they will handle 75amps running through them. More than likely they will get very hot and you will see the insulation deform, melt or worse burn.

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    • #3
      Originally posted by SunEagle View Post
      To handle 75amps continuously you really need wires & insulation sized to handle more than that. If the wires that are connected to that meter are really #12 AWG I seriously doubt they will handle 75amps running through them. More than likely they will get very hot and you will see the insulation deform, melt or worse burn.
      As long as they can handle 40amps. But i think no way of knowing in my situation. Yep they are all 12ga about 5cm long.
      Looking for heavy duty rated watt meters.

      edit: found a 200amp unit that reads 50amp continuous using 8ga wire. Perhaps being so short the wire cam handle it.
      Last edited by Jman; 06-15-2018, 09:21 AM.

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      • #4
        Originally posted by Jman View Post

        As long as they can handle 40amps. But i think no way of knowing in my situation. Yep they are all 12ga about 5cm long.
        Looking for heavy duty rated watt meters.

        edit: found a 200amp unit that reads 50amp continuous using 8ga wire. Perhaps being so short the wire cam handle it.
        Something funny about wires. If they are exposed to high currents over a period of time the insulation tends to get brittle and at some point the metal of the wire becomes what we call a "fuse" because it melts.

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        • #5
          Originally posted by Jman View Post
          edit: found a 200amp unit that reads 50amp continuous using 8ga wire. Perhaps being so short the wire cam handle it.
          Length makes no difference. FUSING CURRENT on 8 AWG is 472 amps. Maximum load current in free air is 55 amps on 90 degree insulation. .
          Last edited by Sunking; 06-15-2018, 07:34 PM.
          MSEE, PE

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          • #6
            Originally posted by Jman View Post

            ....Perhaps being so short the wire cam handle it.
            Length of the wire has no effect on the current carrying capacity, it's still n Ohms per inch. Enough amps and the ohms causes heat, 1" or 6 feet

            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

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            • #7
              Originally posted by Mike90250 View Post

              Length of the wire has no effect on the current carrying capacity, it's still n Ohms per inch. Enough amps and the ohms causes heat, 1" or 6 feet
              Thanks. Well that says to me these watt meters are not safe at their fony advertised rate. I guess if the wire stays cool all is fine. Can the wires get luke warm? No way for me to know if these meters drop voltage.

              if someone could direct me to proper high
              cutrent compact watt meters. Please.

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