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Thread: Diesel Generator 12volt battery cable sizing

  1. #1
    Join Date
    Aug 2015
    Albuquerque, N.M., USA

    Diesel Generator 12volt battery cable sizing

    I am getting ready to replace our battery and cables for our model DGDB, 125kVA, 480V, 3phase generator. But am having trouble determining the size of the 12V battery cables. The engine specifications says the battery capacity is 460 amps minimum at ambient temperature of 0 Celsius (32 Fahrenheit). Right now i have a 12volt, 4D-XHD, CCA 1000 interstate battery. But the marking on the wiring has worn off. Is there a table i can use or equation that can help me. The length of the cable is less than 2 feet.
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  2. #2
    Join Date
    Apr 2009
    Williamsburg, VA
    These charts may be of some help:

    With the cable length so short, you could just buy some short cut pieces from the local warehouse and compare sizes.

    To do the math you would need to know the highest current the starter can draw under the worst conditions. You can't really assume what's there (existing) is correct, tho it's obviously worked for some time.

    As batteries and their cables handle a high current for a very short time, typically 2-4 seconds with a maximum of 15, they can handle much more current w/o degradation or destruction than if they were run for hours.

    if I had to take a wag at your install, I'd probably go 1/0 or 2/0 cable.
    Electricians do it until it Hertz!

  3. #3
    Join Date
    Dec 2012
    Placerville, CA, USA
    The principal concern with starter motor cables is to minimize voltage drop rather than to have a high NEC ampacity (long term heating).

    Looking at commercial jumper cable sets, the biggest you are likely to find, for large diesel trucks, are #1 copper clad aluminum or #4 copper. And that is for a ten foot or longer cable, both positive and negative. I do not see any reason at all to use larger than that for a two foot battery to starter solenoid jumper.

    But if you have the tools to crimp them #1/0 or #2/0 will certainly do the job.

  4. #4
    Join Date
    Mar 2016
    The Motor City, Michigan USA
    Other principal concerns are cable heating and being flexible enough to isolate engine vibration from the battery terminals.
    Battery terminals are readily available in sizes up to 4/0:

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