Battery Switch and Battery Cable Size

Electrical and electronic topics for small boats
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Battery Switch and Battery Cable Size

Postby WhaleeMike » Fri Mar 02, 2018 10:23 am

[Separated from another thread whose topic was battery cable size selection.--jimh]

How would [battery cable size, battery location, engine location, and switch location] work if I put a Perko battery selector into the mix?

Would I put [the Perko battery switch] in the console and run back a single pair [of battery cables] to the motor, or would I run back two pairs [of battery cables] and have the switch near the motor?

Advantages or disadvantages for each option?

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Phil T
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Location: Was Maine, now Kentucky

Re: Recommended Battery Cable Size

Postby Phil T » Fri Mar 02, 2018 1:29 pm

I ran a 1986 Montauk and now have a 1992 Outrage 17.

In both boats, I moved the battery to the console for weight redistribution and protection. I ran a single set of battery cables from the engine to a main battery switch mounted inside the console.

From the switch I ran a set of wires to the battery. A second smaller set of wires ran to a bus bar to run all the accessories.

For a 17' boat, I recall using 20' of 2 awg duplex marine tinned battery cable to the switch.
Member since 2003
1992 Outrage 17, 1992 Evinrude 115

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Don McIntyre - MI
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Re: Recommended Battery Cable Size

Postby Don McIntyre - MI » Sat Mar 03, 2018 12:19 pm

I would be reluctant to mount a battery switch outside,exposed to the weather..... even if the directions states its waterproof. And that eliminates the need to run two pair of fairly thick cables through a limited diameter tunnel.
Regards - Don

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Location: Michigan, Lower Peninsula

Re: Battery Switch and Battery Cable Size

Postby jimh » Wed Mar 07, 2018 3:55 pm

The brand of the battery switch would not have any effect.

The battery selector switch should be located as closely as possible to the batteries. You want to avoid having a long run of cable from a battery without some sort of fuse, circuit breaker, or mechanical disconnect (switch) within a few inches of the battery. See recommended lengths given in the ABYC suggested practices and USCG regulations. Check those sources for authoritative information.

In general you would NEVER have two batteries under the center console and run four conductors back to a switch near the stern. That makes no sense at all in electrical circuitry, violates general practices, and would tend to expose the switch to weather, all disadvantages, and for ZERO advantage.