0.6F AC Ripple Current Soaker-Upper

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  • BackwoodsEE
    Solar Fanatic
    • Jun 2017
    • 217

    0.6F AC Ripple Current Soaker-Upper

    This is what 0.6 Farads of 80V capacitor with a total of less than 1 mOhm ESR looks like. It will be going in parallel with my 48V battery bank to soak up the severe ripple current from an 8 kW inverter (Outback Radian).

    240D88D2-62FB-4739-963B-6CCBEDF3851E.jpeg0278635E-F428-4433-A5B2-D27697768E28.jpeg The bus bars were cleaned with Scotch-Brite, per advice from Sunking, wiped clean, and coated with a conductive anti-oxidant compound, and then the bolts torqued tight. Spec for the electrolytic capacitor terminals was 25 in/lb. I cranked the 1/4
  • BackwoodsEE
    Solar Fanatic
    • Jun 2017
    • 217

    #2
    I did a test of the ESR using my oscilloscope, a 12V deep-cycle battery, and a low-inductance power resistor mounted to one of the busbars. The scope captured the bus bar voltage at the very beginning of current inrush while I tapped a wire to the battery.

    E4918913-2366-4EB5-8E6D-C6ED5E77334E.jpeg

    A quick calculation of the voltage at the base of the ramp confirmed that the ESR of three of the paralleled capacitors is equal to a third of their 5.5 mOhm rating. There was no measurable resistance from the terminal connections.
    Last edited by BackwoodsEE; 01-22-2018, 01:35 AM.

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    • Mike90250
      Moderator
      • May 2009
      • 16020

      #3
      What's the freq spec of the caps - will they go down to 60hz ?
      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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      • bcroe
        Solar Fanatic
        • Jan 2012
        • 5198

        #4
        Thats pretty, guess the next test is ripple reduction with your source feed. At that point I would check
        ripple at the favored load, and also at the far end of the cap busbars. If the latter is less, you could gain
        that advantage by feeding the source into one end and connecting the load to the other end of the busbar.
        My expectation is any cap works down to DC, the high frequency end is limited. Bruce Roe

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        • PNPmacnab
          Solar Fanatic
          • Nov 2016
          • 425

          #5
          I've been playing with some grid tie inverters and the input ripple surprised me, a large percentage of the DC voltage. They use just enough capacitance to keep it stable with nothing to to store PV energy between current peaks.. I just bought 500 electrolytics and it dawned on me that these would make a pretty cheap and robust .6F capacitor. I keep about 40K on my raw pv bank now.

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          • bcroe
            Solar Fanatic
            • Jan 2012
            • 5198

            #6
            Originally posted by PNPmacnab
            I've been playing with some grid tie inverters and the input ripple surprised me, a large percentage of the DC voltage. They use just enough capacitance to keep it stable with nothing to to store PV energy between current peaks.. I just bought 500 electrolytics and it dawned on me that these would make a pretty cheap and robust .6F capacitor. I keep about 40K on my raw pv bank now.
            Maybe they are trying to avoid input electrolytics. What percentage ripple did you see, MPPT is
            pretty broad and may not care? Now I suppose I will have to take a storage scope out there and
            measure my DC ripple. Bruce Roe

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            • Sunking
              Solar Fanatic
              • Feb 2010
              • 23301

              #7
              Backwoods do your knuckels drag the ground? Are you are a gorilla?

              Now that I have your attention what is wrong with your picture?

              On the 16 or 14 AWG you way over compressed the terminals crushing them. To the point you split the insulation which is the least of your worries. The real issue is it severely weakened the wires at the ends of the terminal barrel. Kind of asking for a wire to break loose.
              Last edited by Sunking; 01-22-2018, 11:07 PM.
              MSEE, PE

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