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  • need help

    hi i need to wire a electrical windlass on a yacht i would appreciate if anybody could give me the equations on how to work at the voltage drop for a 7meter wire and what SWG i need, the windlass is 600 watt running from a 12v battery

  • #2
    its a 50amp load and ideally you dont want much more than 2.5% - 3% of a voltage drop so your looking at about 0.3V for 14 meters or about 45feet round trip so your looking for a AWgauge 1 or if your brave 2 about 42mm2 for the thicker. Theres a few other options in wiring it but im sure you can have fun workign them out, just be careful of the battery supply if its too small everytime the windlass is used things like gps will see a voltage drop and shut down, not a huge problem but can be a tad annoying

    .3v/50a = total allowable wire resistance 0.006

    0.006/ 14 total lenght in meters = 0.0004Ohms/meter

    look up standard wire gauge tables see what units they are using some are ohms /km and choose the wire with the closest but lesser resistance. AWG2 is 0.512664ohms/km and AWG1 is 0.406392 however its worth checking the details of the wire you buy as it aint going to be cheap. if your fitting a three wire system you will still only need to count the length there and back as only 2 out of the three are powered at any one time.

    (this is a saturday night suggestion, if in doubt contact the manufacturer as incorrect wiring may casue damage)
    you can take it with a pinch of salt, but i prefer it with a nip of whisky


    • #3
      Cheers for that