Battery Cable Gauge

[hellosailor]

Piper-
Let's see...The difference between a 100% battery and a 0% battery is all of one volt, from 11.7 to 12.7 more or less. You're talking about taking a 12.7 battery and dropping either 3% or 10% to your light bulbs, that would change the voltage to 12.3 or 11.43.

The bulbs will last longer, but do you really want to run bulbs at 11.43 volts, when they are designed to run at 14.4 volts (alternator voltage) not '12' in the first place?

I wouldn't bother ripping out good wiring to upgrade it, but if I was laying new wire--I'd spend for the thicker stuff. Once you buy good crimp connectors and all the other stuff, the difference in the wire isn't much of the total damage anyway.<G>

Same thoughts for the battery cables. If you are installing new, run the numbers and buy the thickest you can. Cable terminations (having the lugs properly crimped and secured tight and clean) can make as much difference as the cables, so make sure they are made up correctly not just squashed on.

If you consider that every 1/10th of a volt lost in the battery cables means your engine/alternator/charger are going to have to work harder to beat that cable loss, every time, the cables seem cheaper compared to the fuel they can save, too.

[GordMay]

Originally Posted by Wilmington Piper

...I have read that 16 gauge is usually standard for running lights, fans, etc. On even a boat as small as mine, I could improve the voltage drop from 10% to 3% by jumping to 12 AWG. Is it worth it in cost of wire over voltage drop?

Within reason, larger wire is always worth the investment (IMHO).

If you look at the charts I previously linked, you’ll see that #16AWG Copper wire is suitable (@ 3% Vd) for 75 Amp/Feet; which will be adequate to run a total load of 5 Amps 60 Watts) over a round-trip distance of 15 feet (about 7.5 ft. from panel), or a load of 2.5 A (30W) over a distance of 30 Ft (15' from panel), or the 2.5 A load 60Ft (30' from pnl).

Up-grading to #12AWG Cu. would increase your capability to running the 5A load about 30 round-trip Ft (15' from panel).

[Aqua Vitae]

Alright, thanks guys. I have decided to run varying gauges depending on the application. Probably going to go with 14 for lights, 12 for dc plug-ins. Other than that, I don't have much but a pressure water pump. Overall, probably 4 gauge for a 4 foot run of batt cables.