View Full Version : What gauge battery wire?

02-15-2010, 05:49 PM
I purchased the BlueSea add a battery system and I'm going to install it next weekend. The boat is 2007 Moomba LSV with 325 stock engine. I'm trying to figure out how many charging amps I get from the Alternator so I know whether to purchase #2 wire or #4 AWG wire and corresponding fuse. This wire will be used between switch and the auto charging relay to the batteries.

Charging Amps / Minimum wire size* / Fuse rating
60 / #6 / 80 Amps
80 / #4 / 110 Amps
100 / #2 / 150 Amps
120 / #1 / 175 Amp

thank you

02-15-2010, 06:04 PM
What is the wire gage being used currently? If I understand the question correctly, and your Add-A-Battery install is close to your current battery, go with at least the same size as currently being used. 4-gage seems real common, and is readily available.

If you are splitting things out with some distance between the batteries, you might consider going a size larger, but know that done correctly, the Add-A-Battery should never see more than charging current. When in doubt, bigger is better than smaller for battery wiring.

STUDY AND FOLLOW THE OVERCURRENT PROTECTION RECOMMENDATIONS CLOSELY. They are there to prevent fire and/or explosion in the event of a short-circuit.


02-15-2010, 06:12 PM
Okay thank you. I do plan on having one battery further than the other so I'll go with the #2 size. I like your idea that over is better than under. I was going to try and squeeze one battery under neath each side of the bow cushions but not sure if I can find a battery with such a low profile. I'm thinking extra ballast here...lol.

thank you

02-15-2010, 08:48 PM
Ausbill, If you have the stock Alternator than your system will never see more than 75 amps. Which means 4ga will be plenty for what your doing. In most cases bigger is better but your not going to see any added benefit over 4ga unless you increase your charging capabilities.

02-15-2010, 10:13 PM
My BEP VSR came stock wired with 2/0.