wiring - 30' catamaran homebuild

[Hunky]

I live up by latitude 64.5, very rural, no boat electricians here or not able to get one here - so there's that. I also have wired several houses, but not boats.

I'm on a strict budget (retired) and still need much hardware purchases, so that taints my thinking. I have in stock an 8 place circuit board. So my question: is it a problem to wire a circuit through a circuit breaker on this panel and then have it run to a fuseblock to break out several items. The circuit breaker would be a convenient on/off switch and protect the wire to the fuse block. The fuseblock would then protect each device wire that runs from it. An example would be cabin lights with several different wire runs or nav lights including the running lights, steaming, anchor/tricolor, and spreader if not others. Also electronics with various instruments - gps, ais, depth, wind.. etc.

I'll probably launch with a minimum of what I need, but the 8 position panel limits future expansion should I get radar, windlass. The more items I can break out to fuseblocks, the better the future, I suppose. Another option I'm thinking of is some of these - like instruments or lights, could skip the circuit breaker and just use a fuseblock with on/off switch before it.

I'll throw some pics on just for interest. The floor plan, where the circuit panel lives, the image looking forward shows the center storage area where i can break out fuseblocks for the lights (nav, mast, etc) and the 12v battery will live in the lower left of the bench. A start battery might live behind cabinet with VHF radio for two 18hp outboards. Also I've been kicking around ideas and spending too much time on autocad - maybe can throw in some screenshots hat don't represent my final thinking.

Also, using good tinned wire and marine connectors. For topside I have a cuddy cabin that will have a 6 position switch for various lights on mast and nav.

thanks!

[Boatguy30]

Outboards don’t need starting batteries. I’ve cruised something close to 25,000 miles on my 34’ cat. 8 switch panel and 2 6 volt GC2 batteries. Added a separate fused switch off the main 12v bus for a water maker last year.
Anchor light
Running lights
Electronics: gps and autopilot
Cabin lights
Refrigerator/ Propane solenoids control
VHF
Accessory: 2 12 volt outlets
SSB

Have a separate 50 amp breaker from bus to my 8 hp Yamaha so I can turn off changing when motoring with batteries near full charge Andy when I remember I turn off on passage and when boat is unattended to avoid theft/shorting issues.

[Hunky]

Originally Posted by Boatguy30

Outboards don’t need starting batteries. .

Great to hear how others do it. For the start battery I was thinking just a motorcycle type battery - manual recommends only 40 CCA. I could do without, but was also thinking of a lithium battery in the 200-280 amp range (4 cells) although I hate to bring that up as it has some controversy still. That complicates it a bit. The more simple the better. Due to budget, I may end up with a small gel or AGM for now.

So I still assume you fuse any wire that branches off from your circuit breakers, such as each wire for something off the Electronics - gps and autopilot, and similar for others? I can see, depending on length of run and total draw, running a heavier gauge, say 14 or 16 ga, from the breaker to a small bus to break out LED cabin lights on 18 ga, for example. The breaker protects the larger wire, and fuses for smaller gauge wires. That's how I understand it, but maybe not necessary in the real world?

[Spot]

Originally Posted by Hunky

Great to hear how others do it. For the start battery I was thinking just a motorcycle type battery - manual recommends only 40 CCA. I could do without, but was also thinking of a lithium battery in the 200-280 amp range (4 cells) although I hate to bring that up as it has some controversy still. That complicates it a bit. The more simple the better. Due to budget, I may end up with a small gel or AGM for now.

I find motorcycle batteries (flooded and AGM) to be more trouble than flooded lead acid lawnmower or deep cycle marine or RV types. Will you be starting the motors at the helm remotely or alongside each?


I am also mid re-wire on my boat, thanks for the the thread and pics and diagrams!

[Boatguy30]

There are 3 runs of 12 gauge to various parts of the boat for the cabin lights then goes to 18 ga. The vhf, gps, autopilot all have their own fuses in the wiring harnesses. There is also a main 100 amp fuse inside the battery box and a 40 or 50 on the 400 watt inverter that ties into the main pos bus which is about 5’ from the 100 amp fuse.

Check out what La Paz yacht services/ Rich Boren is doing on lithium. He has 180 amp/hr in a single group 27 foot print. What I would probably have if not already set up with the 6v. Maybe on the next boat!

[Hunky]

Originally Posted by Spot

I find motorcycle batteries (flooded and AGM) to be more trouble than flooded lead acid lawnmower or deep cycle marine or RV types. Will you be starting the motors at the helm remotely or alongside each?

Thanks for the reply Spot. A guy on a facebook group Multihulls Appreciation really swears by the motorcycle battery - he even uses the lithium ones. That's where I got the idea - no experience otherwise. For my cat, I like the idea of light weight, but curious what troubles you find with them.

I would be starting the outboards at the helm. Picture of that.

Picture of battery setup if I go with start battery - not all fuses drawn in yet. That 125 amp fuse on the battery may not be right yet, maybe too big- just a place holder for now. Also pic of cuddy switches for nav lights etc. Room for a depth/wind display to the right of the switches.

[Hunky]

Originally Posted by Boatguy30

Check out what La Paz yacht services/ Rich Boren is doing on lithium. He has 180 amp/hr in a single group 27 foot print. What I would probably have if not already set up with the 6v. Maybe on the next boat!

Thanks again! How do I find La Paz/Rich? I found them on google but not yet finding their lithium stuff. https://lapazcruiserssupply.com/about-us/

[Spot]

Originally Posted by Hunky

Thanks for the reply Spot. A guy on a facebook group Multihulls Appreciation really swears by the motorcycle battery - he even uses the lithium ones. That's where I got the idea - no experience otherwise. For my cat, I like the idea of light weight, but curious what troubles you find with them.

I would be starting the outboards at the helm. Picture of that.

Picture of battery setup if I go with start battery - not all fuses drawn in yet. That 125 amp fuse on the battery may not be right yet, maybe too big- just a place holder for now. Also pic of cuddy switches for nav lights etc. Room for a depth/wind display to the right of the switches.

My data for battery life is a simple comparison between all of the things in the garage over the last 30+ years. Motorcycle batteries cost more and are useful for a shorter period than any other flooded lead acid battery such as lawn tractor or vehicle-boat-RV types. Typically I get 2-3 years from a motorcycle battery and 4-6 from the others. I do not have Lithium battery experience for vehicles. If you have the right charge controllers to support them and weight is an important factor then they may be for you. For me and my lowbrow tendencies a regular battery down low in the mono-hull is just right.

[Chotu]

As long as all the currents add up properly (ie: what’s the load on the single breaker in the panel with everything turned on?), then it’s not a problem. Also double check you aren’t overloading any negative return paths.

It may even be said your design has more protection than just a standard panel.

Some issues: bring a LOT of fuses. If something shorts, you may blow through several trying to figure it out.

May I also say your build looks fantastic! Great job on the finish work.

[CharlieJ]

Two points:
1. The bilge pump requires a fuse at the source. The bilge pump mfgr will specify what rating.
2. AWG 18 is not appropriate for branch circuit wiring. ABYC specs a minimum of AWG 16 and the CFR requires AWG 14 as a minimum in boats under its jurisdiction.

The price difference between AWG 18 and AWG 16 is insignificant.

[Paul Howard]

You can always add small panels later.
On my 38ft. open bridge deck/large cockpit catamaran I have a circuit breaker panel in each hull, though the battery bank is in one hull, the hull with the galley, so the circuits to windlass and inverter and lights, etc., relative to that hull are on that panel. Opposite hull with the nav. station has the breakers for the nav. lights, compass light, VHF, GPS and the lights, etc. in that hull.
A large fuse block is near the battery bank to a terminal near the first panel, then a crossover cable to the other panel.
Leave light feeder lines in all runs so you can easily add cables for other equipment as it gets added.

[Hunky]

Originally Posted by CharlieJ

Two points:
1. The bilge pump requires a fuse at the source. The bilge pump mfgr will specify what rating.

Thanks for the reply! That was something I was going to research a bit - the bilge pumps came with fuse holders, if I remember right, and I was wondering about the position. By source, do you mean the source of electricity as in back at the bus bar? Or near the pump? I can look this up.

[Hunky]

Originally Posted by Chotu

As long as all the currents add up properly (ie: what’s the load on the single breaker in the panel with everything turned on?), then it’s not a problem. Also double check you aren’t overloading any negative return paths.

May I also say your build looks fantastic! Great job on the finish work.

Thanks Chotu for the reply. Good points and thanks for the compliment. I'll forge ahead, knowing others may do similar - thanks to all the replies.

[Hunky]

Originally Posted by Paul Howard

You can always add small panels later.
On my 38ft. open bridge deck/large cockpit catamaran I have a circuit breaker panel in each hull, though the battery bank is in one hull, the hull with the galley, so the circuits to windlass and inverter and lights, etc., relative to that hull are on that panel. Opposite hull with the nav. station has the breakers for the nav. lights, compass light, VHF, GPS and the lights, etc. in that hull.
A large fuse block is near the battery bank to a terminal near the first panel, then a crossover cable to the other panel.
Leave light feeder lines in all runs so you can easily add cables for other equipment as it gets added.

Good stuff here! I looked up your profile to see if I could find anything on your boat - I see you replied in a thread on Canadian PNW sailing. I may be heading south to somewhere around there eventually - but I'm getting old fast.

Time to rethink my electric system now that I've a bit more confidence in what I'm doing.

[NorthCoastJoe]

My vote for lawn tractor batteries for starting. I use them on my full-sized tractors and they hold up. No other electronics just starting. I also use a lawn tractor battery in my motorcycle. I get 4+ years out of a battery.