I am in the process of adding a second battery and isolator switch. We have a Honda 9.9 with a 6 amp alternator. I am curious as to the proper gauge cable needed for this sort of hook-up. I've seen what appears to be 4 or 6 gauge on other boats but the gauge wire coming from the Honda (factory installed) seems a lot lighter. What is the consensus?
Note: The guy messing with kites, keys and lightning before Ben Franklin was electrocuted. With my understanding of electricity, he was probably an ancestor of mine. Any feedback is appreciated. Tom K.
Gauge wire for a two-battery system in a CD-26
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Tom Kennedy
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Paul McCary
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Wire gauge table
If I'm reading the Don Casey wire gauge table correctly, at a 6 amp max load, you could have a round trip run of 30 feet and still get away with 10 gauge (AWG) wire. But considering 1) the relatively small difference in price, 2) the likelihood that you may someday wire something else on your boat with perhaps a longer run or heavier max load and 3) the bad outcomes possible with too small wires, I'd buy a roll of 8 or even 6. Four seems like overkill no matter how you look at it.
Paul McCary
Impromptu
Pine Island Marina
Impromptu
Pine Island Marina
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Oswego John
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Alternator Wire
Tom,
I'm not sure of the size of what wire you are interested in, the output of the alternator to the isolator or the size of the battery cables. #6 and #4 AWG are some common sizes that are used in starting jumper cables for your car, so I imagine they might be the size of battery cables as well.
The size of the cable from the battery area to the panel would be determined by the total demand of the panel and its distance from the battery. I will include an amp/distance chart toward the end of the post.
The output from the alternator will be about six amps DC max. The output from an alternator will be hardly anything while idling and at low speeds. The amps increase as the engine RPMs increase. The efficiency of the output is greatest at half speed and greater.
Because of a max output of 6 amps which will be much less at most of the operation hours of the engine, you could maybe get by with #12 AWG wire. When in doubt it is always better to go up in wire size than squeak by with a smaller size. Base on a distance of up to 12 feet, 6 amps, 12 volt DC, a safe wire size would be #12 AWG. (see chart). Up to 17.5 feet, #10 AWG. Up to 30 feet, #8 AWG
It is good practice to use tinned, stranded marine grade wire such as produced by Ancor Wire Mfg Co. and others.
Ancor Wire vendor:
http://www.boatelectric.com/ancor.htm
Wire size chart:
http://www.aaasolar.com/ProdLit/Helpful ... RESIZE.PDF
Scroll down to DC Wiring Size
BTW, when calculating wire size for DC Voltage, you should figure on round trip footage. i.e. From the alternator to the isolation switch PLUS the distance from the switch back to the alternator.
Good luck,
O J
I'm not sure of the size of what wire you are interested in, the output of the alternator to the isolator or the size of the battery cables. #6 and #4 AWG are some common sizes that are used in starting jumper cables for your car, so I imagine they might be the size of battery cables as well.
The size of the cable from the battery area to the panel would be determined by the total demand of the panel and its distance from the battery. I will include an amp/distance chart toward the end of the post.
The output from the alternator will be about six amps DC max. The output from an alternator will be hardly anything while idling and at low speeds. The amps increase as the engine RPMs increase. The efficiency of the output is greatest at half speed and greater.
Because of a max output of 6 amps which will be much less at most of the operation hours of the engine, you could maybe get by with #12 AWG wire. When in doubt it is always better to go up in wire size than squeak by with a smaller size. Base on a distance of up to 12 feet, 6 amps, 12 volt DC, a safe wire size would be #12 AWG. (see chart). Up to 17.5 feet, #10 AWG. Up to 30 feet, #8 AWG
It is good practice to use tinned, stranded marine grade wire such as produced by Ancor Wire Mfg Co. and others.
Ancor Wire vendor:
http://www.boatelectric.com/ancor.htm
Wire size chart:
http://www.aaasolar.com/ProdLit/Helpful ... RESIZE.PDF
Scroll down to DC Wiring Size
BTW, when calculating wire size for DC Voltage, you should figure on round trip footage. i.e. From the alternator to the isolation switch PLUS the distance from the switch back to the alternator.
Good luck,
O J