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cable current capacity

Discussion in 'Electrical Engineering' started by Brian Su, Dec 6, 2003.

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  1. Brian Su

    Brian Su Guest

    Hello,

    I would like to build a pair of car (12v) jumper cables on my own. I
    am thinking of using 4 gauge copper cables, how many amps can these
    carry? Can they withstand 400amps? Or should I go for 2 gauge welding
    coppre cables instead? or would 8 gauge be enough already?

    Thanks.
    Brian.
     
  2. Z

    Z Guest

    I believe most car jumper cables are 25mm sq. Commercial vehicle jump
    leaads are 50mm sq. As American cars are generally bigger engines 35mm
    sq would probably cover it.
     
  3. Don

    Don Guest

    AWG gauge max safe amps
    OO 283
    0 245
    1 211
    2 181
    3 158
    4 135



    http://www.powerstream.com/Wire_Size.htm


    many of these tables available on the web, all wil vary. Most are
    continuous usage, you will probably only need to draw your max current
    during the actual starting of the other car.

    But, at the cost per foot of 4 and 2 awg wire (not including your
    clamps), you can't beat buying these already made.
     
  4. You anticipate jump starting a Yugo or a Cat D10 (it makes a difference)?
     
  5. Walter Loos

    Walter Loos Guest

    The main issue is not, if they can withstand thr amperage, but the
    voltagedrop if you use thinn cables.
     
  6. John Gilmer

    John Gilmer Guest

    4 GAUGE is about as heavy as is used in "normal" circumstances. As
    indicated, even this size is hard pressed to carry the necessary starting
    current.

    But the "fact of life" for car to car jumping is that, usually, what the
    really need to do is put enough charge into the "dead" battery so permit it
    to barely turn the engin over. The fatter the charging cable the more you
    can charge the "dead" battery and the more current will be available to
    "help" when the dead car's starter is engaged.

    When I had cheap cables I would connect the two systems and keep the good
    car running for as long as I had patience (2 or 3 minutes) and THEN tried to
    start. I have used this technique to jump start a Buick Roadmaster from a
    4 cylinder TOY.


    I now have a near "top of the line" set (#4 from Wal Mart) but haven't used
    them yet. They are quite heavy.
     
  7. SQLit

    SQLit Guest

    Welding cable is the best bet for high amps. Then MTW ( machine tool wire,
    whole lot a little tiny wires, Humor). If you have to carry them far I would
    stick to 4, clamps are important also. Check the connections to the clamps
    and let that be your guide. I made a set a long time ago and had to use
    terminal lugs on the ends so I could make the connection to the clamps. They
    always got warm around that bolted connection.
     
  8. Brian Su

    Brian Su Guest

    Yes this would work but it can take a very long time to charge up the
    dead battery b4 it has enough CCA to start the engine. I've tried this
    before, using a low quality jump start cable, 12gauge to jump a 1.5L
    petrol engine car from a 1.8L car. It took about 5 mins and lots of
    revving on the 1.8L car and the cable heated up ALOT, it nearly melted
    because I engaged the 1.5L car's started several times while the
    battery was being charged.

    If I had a good pair of cables back then, I'm sure it would have
    started up almost instantly w/o even having to run the other car's
    engine.
     
  9. Z

    Z Guest

    My jump leads are 50mm sq and rated to start an engine up to 9 litre
    (9000cc)
     
  10. According to Greek Internal Installation Code, the wire gauge that can
    handle safely that ampacity is 150 mm2.
     
  11. Neil Swanson

    Neil Swanson Guest

    Constant or Cyclic? Remember jump leads are short duration items, it is
    acceprable for them to heat (Up to a point). Not withstanding anyone elses
    point, I have the largest set I can keep in the car along with all my test
    instruments. 50mm sq. I have used 150mm in an emergency, but that is
    Portable Primary Earth gear for the 33kV Distribution Network. Large
    unweildy and you would have no space in the car. (Rated for a fault
    capacity of up to 1000MVA. You hopefully don't get that from a combustion
    engine alternator!)

    Neil
     
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