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    kimo10's Avatar
    kimo10 Posts: 1, Reputation: 1
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    #1

    Jun 2, 2010, 11:10 AM
    How to calculate the dc short circuit current for a dc system
    I have a battery string of 60 single cell batteries making up our 125VDC main station service for our power plant. Each battery is rated as follows:
    Lead-calcium type storage batteries, Exide F, FTC-15 , Cat. no. 73336, Nominal capacity 1180AmpHr, 1.205-1.220 specific gravity at 25 degrees Celsius (77 degrees Farenheit). They were manufactured on 1/12/1988.
    How do I calculate the DC short circuit current from this source ?
    InfoJunkie4Life's Avatar
    InfoJunkie4Life Posts: 1,409, Reputation: 81
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    #2

    Jun 3, 2010, 05:51 PM

    In what configuration are they connected. All series, some series some parallel?

    I'm not sure what you mean by short circuit current, someone else here may. I know you calculate dc loads and such by using the following equations.

    P=EI

    and

    E=IR

    E = Voltage (In Volts)
    P = Power (In Watts)
    R = Resistance (In Ohms)
    I = Amperage (In Amps)

    Good Luck...
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
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    #3

    Jun 3, 2010, 06:45 PM

    You need to find the ESR of a battery and add them up. ESR is a good way to determine the health of a battery. ESR is the Effective Series Resistance.

    The manufacture would know this and if you had the spec of Cold Cranking Amps, you can generally back out ESR.

    Your sort of looking for the slope when the battery is heavily loaded.

    Battery testers can run an I-V on the battery or they can just do it with a load.
    Zog's Avatar
    Zog Posts: 7, Reputation: 1
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    #4

    Jun 8, 2010, 10:02 AM

    Best way is to use the DC module in SKM.

    Or measure the battery bank Impedance (Meggers EBITE tester will do this), Isc will be Vt/Z

    Or for a good guestimate, the Isc will be 20x the 3hr discharge rate, if you do not need an exact number this works fine.

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