Re-Wiring a Really Old Boat

[delmarrey]

Since your in fresh water with a wood boat your main concern will be dry rot!

A good splash of saltwater over the entire boats once in awhile will be good for it. The other alternative is white vinegar over all the seams and rock salt in the bilges.

[hellosailor]

Jeff, one of the largest battery mfrs in the US explicitly told me that it was OK to use their deep cycle batteries for engine starting, as long as the starting current that was required could be safely provided by the battery. i.e., if your starter motor takes 1.5kw and the battery can handle impulses of 2kw, you're well inside the safety margin. So check the rating of your starter motor(s) and as long as your deep cycle and wiring are robust, you're OK. That also means the fusing on your battery cables needs to be sized to hold under that load.

Given all the choices though, I'd like to see at least one--but just one--battery reserved for starting and used for nothing else. It would be a waste for you to use part of your house battery capacity for that, when you might be able to use a smaller, cheaper, lighter, Group24 or Group 27 SLI battery just for starting. They're cheap enough to be painless. One on one engine would be enough, with provision to use the genset and house bank or crossover if you need to start on the other engine. A set of jumper cables, or a permanently installed switching setup, either way.

AGM's are going to be expensive and need replacement more frequently than you'd want, unless you have an external regulator and treat them right, so please DO invest in that ahead of everything else. With 500AH of AGM capacity, you could in theory use 125-250A of charging power very efficiently.

[Rugger8]

ok, thanks everyone.

I am on the Hudson river, about 50 miles north of the Manhattan. So, at full tide I get salt water where I am at, but most of the rest of the time, it is fresh water or some amount of mixture.

So, it sounds like a reasonable plan to have 1 dedicated starting battery for both engines and then 4 deep cycle batteries for the bank. Then I will have 1 alternator to charge each bank of batteries.

Jeff

[hellosailor]

Jeff-
"Then I will have 1 alternator to charge each bank of batteries."
if you're going to do it that way, I would consider "wasting" my money by putting the same high-capacity externally regulated alternators on both engines, rather than just using "enough" on the SLI battery.
This because alternators and regulators DO eventually fail, and having a hot spare that is already installed and loafing on the second engine, could be a useful thing down the line. (i.e. just add jumpers or throw a switch, and you can still use it for the house bank.)

[Rugger8]

Yeah, that's what I meant. I would put alternators on both engines, but have 1 alternator charging the house bank and the other alternator charging the starting battery. And as you suggest, have the ability to swap that if one alternator fails.

Jeff

[David M]

Despite who is right or wrong about bonding a wood hull, if you are not getting excessive corrosion now, I would not change a thing.

The better thing to do with your alternators is to have them both charge your 12v house system. This way if one fails, you are not stranded, plus they can both share the house load and provide more power to the house load than if you had just one powering your 12 VDC system.

This is how I have my boat wired and it's a big myth that you cannot have two alternators powering a DC system in common. If they are identical alternators they will share the load just fine. There is no such thing as feedback. All an alternator knows is the system voltage and will react according to any voltage changes by producing more or less current...period. I have each of my alternators power running through each of their own shunts to each of their own ammeters and therefore know as a fact this to be true. They always seem to balance out within a few amps of each other even when the engines are running at different RPM's, except when at extreme differences such as if one is idling and the other is running much faster. Most alternators do not charge much at all if any at an idle...unless you rev it up a bit to get a field started and then back it down some....I'm off on a tangent now.

What you do to provide an isolated start battery is to run both your alternators hot leads back to your house battery and then use an isolator (a big diode) or combiner (a voltage controlled solenoid that opens when the start battery voltage drops to a specified level) between your house battery and start battery to isolate your start battery so your house load does not draw down your start battery voltage. Of course you want to set up your battery switches so that the ALL position literally means that, in case any one component fails all your hot sources and loads become common with each other.

[GordMay]

USCG “Navigation and Vessel Inspection Circulars” (NVIC)
➥ Navigation and Vessel Inspection Circulars (NVIC): USCG

Including:
7-95 “Guidance on Inspection, Repair and Maintenance of Wooden Hulls”
➥ http://www.uscg.mil/hq/cg5/nvic/pdf/1995/n7-95.pdf

[SV Demeter]

You might want to examine your use and charging systems (AC and DC) and decide if AGM batteries are the way to go. They have advantages but only if the rest of your system is able to take advantage and can keep the AGMs happy. You might find that conventional flooded batteries are the best value.

I think you are making the right decision regarding the bonding. Im a firm believer in inspection and maintennance and on a wooden boat replacing some metal underwater fittings periodically is a lot cheaper and easier than dealing with planking and rot issues. I doubt if you have not yet had any that you will. My alternative to the galvanic isolator is to simply not plug my boat in. I found my zincs last a lot longer if I do not leave the boat plugged in all the time.

[GordMay]

Originally Posted by SV Escape Plan

... My alternative to the galvanic isolator is to simply not plug my boat in. I found my zincs last a lot longer if I do not leave the boat plugged in all the time.

I'd strongly recommend installing a Galvanic Isolator or Iso' Transformer if you EVER plug in to shore power.

Galvanic isolators are installed on boats to prevent galvanic corrosion when the boat is connected to a shore power source; however, that is not their only important function.

The fact that a galvanic isolator is installed in series with the safety grounding conductor of the shore power cable makes this product a critical link in safety grounding of the boat.

If an electrical fault on the boat occurred and this safety grounding path was interrupted, personnel on the boat or bridging the boat and the dock, and anyone in the water near the boat could be subject to serious electrical shock or potential electrocution, and/or drowning.

[Ron Spilsbury]

I also have a 1947 wood boat but it is in salt water. About 15 yrs ago I replaced the bonding of the under water fittings. Next year during its annual haul out I found mussels, barnacles and worms attached to all the fittings. I then removed the bonding to all those fittings that were isolated and connected by rubber hose. They are now clear of animal and plant growth. The remaining hardware have zinc anodes but still attract sea growth. The plastic covered depth sounder also attracts sea growth.

Electrically, the batteries are 32 volts and are grounded through out and include the grounding plate on the bottom. The 110/230 ac system has safety grounds that do connect to the ships ground. The shore supply comes through an isolation transformer to the 32 volt, inverter/battery charger. The inverter is a pure sine wave 3 kw. There is a 60 amp alternator on the main engine. There are 3 80w solar panels in series.

There are two 12 volt battery systems. The 200 aH is for most of the house duties. The smaller one is just the starting battery for the genset which has it's own alternator.

The hull fastenings were iron ships nails. Because of flexing the rain water made its way in to the nails and many were rusting and swelling. We refastened with stainless screws and that has worked for the last 12 years. The old iron nails were set, dabbed with blue steel rust convert, wetted with epoxy resin, then covered with epoxy putty and finished with surfacing putty before painting.

The boat is kept out doors year round and only tarped when there is a problem that is waiting for warmer and drier weather. Rain water is the main enemy.

The only justification for most of the above approaches is so far they are working.

Ron

[hellosailor]

Of course there is one point in favor of AGMs on a wood boat: None of that pesky acid electrolyte is going to get out and stain or eat any of the wood.

I don't say AGM is right all the time or in all places...but I've lost pants, shirts, and a winter parka to electrolyte over the years. I know, I should wear more plastic.<G>

[S&S]

Originally Posted by delmarrey

Since your in fresh water with a wood boat your main concern will be dry rot!

A good splash of saltwater over the entire boats once in awhile will be good for it. The other alternative is white vinegar over all the seams and rock salt in the bilges.

Here on the Lakes we have woodies that have been in fresh water for over 100 years. Rot growth is dependent on relative saturation. Keep the bilge dry and skip the salt.

Oh, and Do Not Bond. Calder is wrong on that one.

[Rugger8]

Thanks again everybody, I do appreciate all the responses. I guess the bonding issue is truly a hot button issue. But I will go with what has worked before and that is simply no bonding and zincs on the shafts and ruddders. I do have the galvanic isolators bought and installed already, so will just keep them, which will help with the safety ground issue. Not a big fan of the traditional lead acid batteries, just not something I want to deal with in terms of forgetting to refill, etc. The Odyssey batteries seem to have a lot more CCA's then even starting batteries. So, does anyone see a reason why I should not go with 1 battery for exclusive use as a starting battery for both engines and then 4 batteries for the house. Plan is all 5 batteries would be the Odyssey group 31 batteries.

Thanks,

Jeff

[S&S]

Your proposed rig should work fine. (as long as the start battery has enough capacity). To take advantage of the Odyssey batteries, you really may want to think about getting a couple of alternators ...and maybe something like a Balmar Centerfielder to tie them together.

[Rugger8]

I apologize for my lack of knowledge on the alternators as I have not really started to do a lot of work on that yet, so help is appreciated. I know that there are some shops that will rebuild the insides of my current generators and convert them into alternators to maintain the same look. But I wonder about the output versus buying a modern professionally built alternator. I presume I should be able to use off the shelf alternators that look different, but provide better output than a rebuilt generator from my original Hercules engines.

S&S - the Balmar centerfielder, what is the purpose of that? To combine 2 alternators and provide one source of power to the batteries?

Thanks,

Jeff