Battery cable sizing.

c_witch

c_witch

.
Dec 20, 2010
294
Yankee Condore 21 Halifax
Hiee,

I'm just wondering what size cables to run from our house bank to the battery switch. We'll be using 2 150 amp-hour deep cycle batteries and the longest run from the terminal to the switch would be 4 feet or so. All lighting on board is LED with the most power hungry beast being the mercerator pump followed by a laptop computer. Electronics is pretty minimal with VHF and a fish finder/depth sounder. I doubt we'd ever see more then a 30 amp draw thru the cables to feed everything. Also is it advisable to add fuses at the battery terminals and if so what size.

Happy Sailing,
Brina
 
Bill Roosa

Bill Roosa

.
Jun 6, 2006
6,990
currently boatless wishing Harrington Harbor North, MD
Does the bank ever get used to start the engine? What is the max rating of your alternator?
Those are, typically, the items that determine cable size.
 
c_witch

c_witch

.
Dec 20, 2010
294
Yankee Condore 21 Halifax
Bill Roosa said:
Does the bank ever get used to start the engine? What is the max rating of your alternator?
Those are, typically, the items that determine cable size.
Click to expand

No we use an outboard manual start. The only power being used by the house bank is for lighting and electronics etc. As mentioned all lighting is now LED and the mercerator pump takes the most juice at 16 amps, but only takes 3 or 4 minutes to empty our msd and then the laptop when running acitively with the screen on takes about 5 amps. So I'm not really sure what size to run from the banks to the 1 2 switch.

Brina
 
Y

yobarnacle@yahoo.com

.
Jun 17, 2011
2
ODay 19 ft Mariner Trailer
c_witch said:
Hiee,

I'm just wondering what size cables to run from our house bank to the battery switch. We'll be using 2 150 amp-hour deep cycle batteries and the longest run from the terminal to the switch would be 4 feet or so. All lighting on board is LED with the most power hungry beast being the mercerator pump followed by a laptop computer. Electronics is pretty minimal with VHF and a fish finder/depth sounder. I doubt we'd ever see more then a 30 amp draw thru the cables to feed everything. Also is it advisable to add fuses at the battery terminals and if so what size.

Happy Sailing,
Brina
Click to expand
Biggest copper cable you can find and afford. I know it seems contrary, but it's true! Thicker the wire, lower the resistance. Resistance is converted into heat. Go Big!

[/quote] Of all the things I've lost during my lifetime, I miss most my mind.
 
M

mitiempo

.
Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
I disagree with yobarnacle. ABYC calls for batteries to be fused within 7", the exception being start batteries. This is best done with an ANL fusehttp://bluesea.com/category/5/21/productline/129 or a MRBF fuse http://bluesea.com/category/5/21/productline/overview/378 as they have the required AIC rating for this application.

The wire should be sized for the maximum load the panel will ever see. If you have a Blue Seas panel rated at 100 amps I would use wire that can handle that load over the distance - both there and back with a 3% voltage drop or less. That works out to 6 awg, but I would use 4 awg. Panels have a habit of gaining loads over the years.
 
Last edited:
c_witch

c_witch

.
Dec 20, 2010
294
Yankee Condore 21 Halifax
Thanx everyone I think that 4 AWG should be quite sufficient to handle our needs now and into the future. I also think that battery fusing is a good idea.

Happy sailing,
Brina
 
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