Windlass Wire Size

Kevin,

I trying to size the wire for my Maxwell 800RC windlass. Every were I look it gives you a different conductor size. The motor is rated at 1000w. I need to run the wiring approx. 25′. What size of wire should I be using?

Thanks,

Mike

Hi Mike,

You can use my marine wiring size calculator or the following equation to calculate your wire size.

  • CM (wire size)= (K*I*L)/E

Where:

  • CM = Circular mil area of conductor.
  • K = 10.75 (constant representing the resistivity of copper)
  • I = Load current in amperes
  • L = Length of conductor from the positive power source connection to the electrical device and back to the negative power source connection, measured in feet.
  • E = Maximum allowable voltage drop at load in volts (e.g., for a three percent voltage drop at nominal 12V, E= 0.03 x 12 = 0.36; for a 10 percent voltage drop at nominal 12V, E = 1.2)

The current draw of a maxwell 800 RC at 12 volts is 83.3 Amps
The conductor length is 25*2=50 feet

  • At 3%, the CM is 124,371 or 2/0 AWG battery cable
  • At 10%, the CM is 37,311 or 4 AWG cable.

It is very common to see 4 AWG cable used on 1000 watt windlasses. A larger wire will reduce the voltage drop at load and the windlass will perform better.

Please let me know if you have any questions,

Kevin

Kevin,
One more quick question. So the windlass will opeate ok on #4 AWG. The on;y time this will make a big difference is when it is under hi load? And as to my calculation the battery output from my batteries is  13.8 V. So this would also help if I choose to run the #4.
Also thank you so much for your help.
Mike

Kevin,

One more quick question.

So the windlass will operate ok on #4 AWG. The only time this will make a big difference is when it is under high load? And as to my calculation the battery output from my batteries is 13.8 V. So this would also help if I choose to run the #4.

Also thank you so much for your help.

Mike

Hi Mike,

Yes. The windlass will operate ok on 4 AWG. The only time you may notice it struggle is under very high load.

In reality, your highest load will be when you are trying to retrieve your windlass. Start your engine before reeling in the windlass (probably a good idea anyway). This will increase the battery voltage which will decrease the current draw, decrease the voltage drop in the windlass wire, and increase the windlass retrieval speed.

Happy boating,

Kevin

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