Catalina 310 battery wiring question

[Monheganlover]

I have a 2002 Catalina 310. The house batteries were replaced a few years ago with two big 18D AGMs giving me a bank of 400 amps. I recently installed a new Victron battery charger and, in the course of doing that, came upon a mystery I am hoping others can answer. In order to thread the new charger DC cables to the battery bank, using an old wire, I fished them through some conduit that was visible under the head when looking from the stern just behind the aft bulkhead after removing the port most compartment covers under the back berth. The wires emerged through an approximate 5"x5" square opening in the starboard corner of battery bank storage area under the settee that is parallel to the forward head bulkhead. There are a few conduits running under the head that carry the big 4/0 positive and negative battery cables to the battery bank.

The mystery is, while I was able to use the old wire to pull the new dc charger cables through one conduit and up through the opening to the batteries, I can't, for the life of me, figure out how one would be able to fish a 4/0 or similar size cable through that same 5"x5" opening. I thrust my flexible fiberglass wire noodler through a conduit, again accessing it below the rear head bulkhead and it went through with no resistance. But, using a flashlight, I could not see any sign of it when looking through the aforementioned 5"x5" port in the battery storage area. My question is, how would one ever fish a big cable through and up to the batteries? I am sure someone here has done it and I must be missing something. There doesn't seem any way to lift the floor under the batteries themselves as that shelf appears to be solid fiberglass. I am stumped...Any advice on how to do this should I ever need to replace one of the 4/0 cables? Thanks!

 

[Ralph Johnstone]

should I ever need to replace one of the 4/0 cables?

Are you sure you are installing AWG 4/0 cables ? These are massive and have an ampacity of 445A. I also notice you have a battery bank of 400 amp-hours. Is there a chance of some confusion between battery capacity and demand here ?

A #2 AWG would be closer to the size you require for a 310 Cat given the lengths and demand on the wiring.

 

[Monheganlover]

They are definitely not 2 AWG. I have some of that lying around from an RV I just upgraded to lithium. I have both 2/0 and 4/0 cable (inverter cable) I am using and the boat cable is similar sized. So, maybe 2/0 given that the boat cable has some bends in it.

 

[dlochner]

Could you provide a few hi res photos? Cable size should be printed on the cable. What size fuse is on the battery cables, that will also give you a clue on the cable size. If it is 2/0 the fuse should not be higher than 300 a.

 

[Ralph Johnstone]

Your first choice for identifying wire size would be to check the lettering on the vinyl jacket.

If that's too faded, then check the wire diameter as shown in the ABYC table.

The only way I can see to get your wire through the 5X5 port is to purchase the correctly sized cable for your boat (much smaller than 4/0) considering

1. the amperage rating of your battery selector (breaker)
2. the demand of your electrical system
3. and the length of wire (X2) to your distribution panel.

If you already have a supply of oversized wire on hand, you will have to find another route to get it to the panel.

 

[Monheganlover]

Very helpful. Thanks. Regardless of the wire size, however, how have others fished the budget wires up into their battery compartments from the conduits under the head compartment?

 

[Monheganlover]

meant "smaller main battery wires"

 

[dlochner]

Very helpful. Thanks. Regardless of the wire size, however, how have others fished the budget wires up into their battery compartments from the conduits under the head compartment?

Fish a small Dacron line first, then attach it to the wire and pull it through along with a second line. Always leave a line in the conduit.

Do not use nylon line as it will stretch when the wire gets a little hung up. I use 2mm braided polyester from Robin. It gets easier with practice and experience.

 

[Ralph Johnstone]

I hate to bring this up but are the old wires still in place ? Not too clear what stage you are at right now. If they are still there and you can use them, make each taped connection as smooth as possible to avoid getting snagged in a tight location. If they're not there, I wish we had spoken sooner.

 

[Monheganlover]

Thanks. Stupid question. Were you fishing something up through the same small opening I have? If so, how did you see or access the Dacron line from that opening as it is so small?

 

[Monheganlover]

Ralph, no. The main battery wires are all new in the last couple of years since an upgrade after I bought the boat. I just am curious as to how others have done it. The only way I got my 8 AWG charger cables through was because I used an old charger wire to pull them. I have only recently decided to do as much in future as DIY after dropping way too many boat bucks on professionals who now charge north of $140 an hour for mechanical or electrical in the Annapolis, MD area where I sail. I am trying to understand how my whole boat is wired so I can fix things myself in the future. Tracing the wiring so I can diagram it all out is a current goal.

 

[dlochner]

Obviously if the wire is too big for the hole, it won't go through. For the first run I use a fish tape, push through the conduit attach the messenger line and pull it back. It often takes several tries and some finagling to get a smooth first run. After that, it is pretty easy.

 

[Monheganlover]

dlochner So, you can usually see your fish tape through the access hole then I guess and, somehow, reach it to tie your messenger line too? I couldn't see the end of my fish tape when I pushed it through the conduit but I guess I just didn't angle it right

 

[dlochner]

It is probably not a true conduit. It is just an open space between the hull liner and the hull. Try going through the opposite direction. If all else fails use an existing wire to pull the messenger line through.

 

[Ralph Johnstone]

The main battery wires are all new in the last couple of years since an upgrade after I bought the boat.

If I understand you correctly (and I'm starting to think I've lost the thread somewhere) you now HAVE these oversized wires in place but are looking to the future should you ever have to replace them ....................

Any advice on how to do this should I ever need to replace one of the 4/0 cables?

Am I correct ?

First thing is you will NEVER have to replace a 4/0 wire as it will always be big enough to accommodate any DC demand you may have.

However, should you every have to replace the 4/0 cable due to, let's say, a drive by shooting, you would be replacing it with something much smaller like a #2 AWG after the dust has settled from the calculations.

Personally, I'm far more concerned about being hit by a meteorite while on the water rather than my #2 AWG cables feeding power from my batteries to the panel ever needing replacement. But that's just me.

Just out of curiosity, who installed the 4/0 wiring which you now have in place. One of these people :

after dropping way too many boat bucks on professionals who now charge north of $140 an hour for mechanical or electrical in the Annapolis, MD area

 

[Monheganlover]

You haven't lost the thread. I have been confusing you I think. I am just trying to understand how I would ever run a large cable if needed and you, collectively, have all answered it for me. I ended up looking up the invoice from when I had the battery and inverter cables added. They are all 2/0. I've attached some photos of them in my battery compartment. To be honest, from a distance, both 2/0 cables and 4/0 cables look pretty close to me..."massive" for sure. At the time, I didn't know anything about marine wiring so I didn't question the wire sizing choice the tech who installed them made. I assume he up-sized them to 2/0 due to the inverter I have and the bow thruster. Good to know I will, likely, never have to replace these wires!

 

[dlochner]

Those look like 2/0 or 00 cables which would be an appropriate size for a largish DC system.

Now, about how the batteries are wired. If the batteries are in parallel the DC+ should only come off one end of the bank. It appears that the loads are coming off of both sides of the bank.

So, before worrying about how to run new cables, the wiring really needs to be sorted out. Since you want to stop spending a lot of money on pros, you'll need to learn the basics. If you are a self-directed learner then head to MarineHowTo.com if you prefer a more structured approach then Nigel Calder has a program for you at BoatHowTo.com. The courses are not free, but they will be well organized and will teach you what you need to know.

For local knowledge in Annapolis, Peter Kennedy is the go to guy. It might be worthwhile to hire him to work with you to sort this out.

PKYS INC Marine Electrical Systems Experts

shop.pkys.com

 

[Monheganlover]

Great suggestions! Thanks. I've bought something for my RV from Peter Kennedy so that is a great idea to have him survey my system and make fixes but talk me through them so I learn.

 

[obxjeff]

8d agm's have around 240amp hours, but around 1400 cranking amps, not the same thing at all.

For a charger to a battery its the charger output amps that need to be sized, an 8awg wire from the charger to the batteries can handle 40 amps and should be all you need. if the charger is an inverter too you need to size for that.

The 4/0 wires are likely correct for a 250amp thruster so leave em.

To answer the original q, pulling a 4/0 without damage through hidden stringers and bulkheads is not possible. Tight bends, gouges, twists, and stretch will reduce the integrity of any wire.

Always have a fuse or beaker on every circuit sized for the smallest wire, with a possible 1400 amps from the batteries even the 4/0 will melt.

 

[Monheganlover]

Very grateful for all the expertise here! And I appreciate the confirmation that 8 awg for my 30 amp charger wasn't overkill. I wasn't comfortable with just 10 awg. I fused the positive wire at 40 close to the battery which is the size of the fuse on the charger itself. It is not an inverter charger just a a single output Victron 30 amp smart charger.