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  • Amp hour conversion

    Hey guys, I am currently replacing the battery pack as the old setup of 16 8l16 batteries was getting tired at 8 years old now. I found a battery pack that has been refurbished and is rated at 600amps at 8hrs, 570amps at 5hrs and 490amps at 3hrs. I would like to know around what this battery pack would be rated at 20hrs so i can tell my xw6048 charger/inverter what it is.
    Thanks!

  • #2
    Draw yourself a nomograph

    https://en.wikipedia.org/wiki/Nomogram.
    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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    • #3
      Not sure it matters because it is a used battery, and no used battery will have rated capacity. Depends a bit on the manufacture, but what you are looking for is the Peukert Factor Constant Factor. In this application from 5 to 20 hours discharge rate is going to be on the order of 1.2 to 1.25 so 600 AH's @ 5 Hour Rate x 1.2 = 720ish AH @ 20 Hour Rate. Just call it 700 AH is close enough.

      FWIW it is not 600 amps @ 8 hours. That would be 4800 Amp Hours. It is 600 AH @ the 8-hour discharge rate as you would be extemely luck if they even have 500 AH @ 20-hour discharge rate left in them.

      Amp Hours = Amps x Hours
      Hours = Amp Hours / Amps
      Amps = Amp Hours / Hours

      600 amps @ 8 Hours = 4800 Amp Hours.
      4800 AH / 8 Hours = 600 Amps

      600 AH / 8 Hours = 75 Amps.
      490 AH / 3 Hours = 130 Amps

      Huge difference.
      Last edited by Sunking; 08-14-2018, 08:13 PM.
      MSEE, PE

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      • #4
        My mistake on writing amps instead of amp hours. I did pretty much the same conversion as you but wanted to make sure i was correct. Its replacing 740ah when new 8 years ago, so i am sure i will be more then happy with it.
        The battery pack is 100% remanufactured with a 2 year full replacement warranty.

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