What size battery cables etc?

[smokey73]

1994 Hunter 40.5

I have searched the forum and haven't found a clear answer so I thought I'd see if I could get an education.

I will be moving the batteries from the starboard lazarette to the port lazarette above the diesel tank and plan to install two parallel banks of two six volt wet cell batteries in heavy duty enclosures. I will also put in a new boat side smart plug inlet so I can use the new smart plug shore power cable I bought. I will also be installing a Nextgen 5.5kW generator in the starboard lazarette. All the critical electrical hookups, including the power transfer switch for the generator shore power connection will be done by a licensed marine electrician. I will, however, be making up the battery cables, and other wires as needed for the installation.

I have read the MainSails thread on making your own battery cables (which is great by the way) and purchased an FTZ non-ratcheting crimper. Looks like a good tool to have. I plan on using FTZ power lugs and marine tinned cables that I can buy from this site but the question is what size. I know I need the lug size to match the battery terminals and the terminals on the buss bar/terminal strip.


Now the question. What size battery cable wire do I need to use so I can get that on order. The new run from the repositioned batteries to the on/of switch will be about 12 feet more or less. Also, will I need to install an inline fuse or breaker near the batteries. Any advice is appreciated. Thanks in advance.

 

[Maine Sail]

1994 Hunter 40.5

I have searched the forum and haven't found a clear answer so I thought I'd see if I could get an education.

I will be moving the batteries from the starboard lazarette to the port lazarette above the diesel tank and plan to install two parallel banks of two six volt wet cell batteries in heavy duty enclosures. I will also put in a new boat side smart plug inlet so I can use the new smart plug shore power cable I bought. I will also be installing a Nextgen 5.5kW generator in the starboard lazarette. All the critical electrical hookups, including the power transfer switch for the generator shore power connection will be done by a licensed marine electrician. I will, however, be making up the battery cables, and other wires as needed for the installation.

I have read the MainSails thread on making your own battery cables (which is great by the way) and purchased an FTZ non-ratcheting crimper. Looks like a good tool to have. I plan on using FTZ power lugs and marine tinned cables that I can buy from this site but the question is what size. I know I need the lug size to match the battery terminals and the terminals on the buss bar/terminal strip.


Now the question. What size battery cable wire do I need to use so I can get that on order. The new run from the repositioned batteries to the on/of switch will be about 12 feet more or less. Also, will I need to install an inline fuse or breaker near the batteries. Any advice is appreciated. Thanks in advance.

Windlass? Inverter/charger? How big an alt? On a 40 footer it is usually 1/0 or 2/0...

 

[smokey73]

Windlass? Inverter/charger? How big an alt? On a 40 footer it is usually 1/0 or 2/0...

Windlass - Yes

Inverter/Charger - No - charger is original but I plan on installing a charger/inverter combo or a stand alone modern charger with a separate inverter some time in the near future along with a battery monitor.

Alternator is 80 amp.

I'd rather go larger in wire size than smaller as the price difference isn't that much. The charger inverter may not be immediately installed so the first step is to move the batteries and I don't want to undersize the cables and then have to replace them. I'm thinking 2/0 is right but hoped to get confirmation for the first step.

 

[Stu Jackson]

Wire size is based on amperage and distance (round trip). There are many, many sources for wire sizing. One of the easiest to read is in the West Marine Advisors:

http://www.westmarine.com/WestAdvisor/Marine-Wire-Size-And-Ampacity

There are also "charts" or tables in almost every single boat electrical book.

Don't forget the fuses.

Good luck, sounds like a good idea.

 

[JK_Boston_Catalina310]

Like Stu said but I find this wire and fuse sizing chart from Blue Sea to be very useful. I have a copy of it on the boat for quick reference when needed.

http://assets.bluesea.com/files/resources/reference/20010.pdf

 

[dlochner]

Like Stu said but I find this wire and fuse sizing chart from Blue Sea to be very useful. I have a copy of it on the boat for quick reference when needed.

http://assets.bluesea.com/files/resources/reference/20010.pdf

Blue Sea also provides an iPhone app. https://itunes.apple.com/us/artist/blue-sea-systems/id576865086

 

[mitiempo]

This is the wire size calculator I prefer: http://boatstuff.awardspace.com/awgcalc.html

Just plug in % of voltage drop desired, length of run, and amp load and it gives you wire size.