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Old 16-08-2022, 12:55   #1
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Isolate Batteries in woody

I am looking to purchase a wood boat. (Please don't talk about how wood sucks etc etc etc, I have another thread where I am learning how many wood hulls are rotting in boat yards and how no one should ever ever ever sail one outside of their bathtub. But if you must go down that trail, please keep it on topic...something like, "a wood boat, you must be crazy. The minute you turn on your nav lights everyone will be electrocuted!" Fair?)

I do not want stray current in the boat, obviously.
Here are the questions:

Where is a good place, in general to put the battery bank?
Should I build an isolated well vented battery box?
What about cooling?

Wiring, is there anything different about wiring a wooden boat as apposed to glass boat?

I will also have to add a shore power system as well. There will be no solar, nor gen set. I will charge off the diesel, I think.

This is an old boat, Alden 42' Yawl, built by Hinckley. Has a 12v system now, but I want to update wiring, lighting, nav electronics and I don't want it to burn to the water line...Ya'll know all that varnish!!!

Thanks
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Old 16-08-2022, 13:19   #2
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Re: Isolate Batteries in woody

Wood is a lot harder to burn than glass fibre, I would not worry about it.
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Old 16-08-2022, 13:45   #3
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Re: Isolate Batteries in woody

Hello,
In general, the battery boxes (I assume you'll have separate "house" and "start" batteries) should be in isolated, well vented boxes that can't leak acid (I'm assuming you'll use flooded lead acid type batteries). You could build marine ply wooden boxes and glass the inside of the boxes. The boxes need to have a good strong lids (in case you do a 360 roll) and should have some way of chocking the batteries inside so the batteries don't shift around.



The boxes should NOT be located in the bilge! They need to be above the level of the cabin sole in case of lots of water getting in the boat (wooden boats can leak a lot). The boxes also need to be very securely attached to the hull structure so they can't shift in bad weather or a roll.


As to your project of re-wiring, I suggest you keep it simple. Yes, allowing A.C. on the boat will complicate things, but I'm assuming you only need it to run some A.C. appliances when you are on the dock. No gen set or battery charger sounds like a good idea. A good alternator with an external regulator on the diesel will be good to charge the batteries. A small solar panel will trickle charge the batts when you are on the dock or at anchor.


Re stray currents; If you use good quality tinned wire, keep wires and connections out of the bilge, you should be ok. There is always the question of whether or not to bond all the metal bits (through hulls, etc.) to the negative side. I won't comment on that...
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Old 16-08-2022, 15:40   #4
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Re: Isolate Batteries in woody

Originally boats in the size range and vintage you are looking at generally had, (by today's standards,) very rudimentary electrical systems.
A batt to start the engine, and 1 or 2 batts to run the navigation and a few interior lights, maybe a circuit for a depth sounder and radio.
A shore power AC system might run a simple batt charger and perhaps an outlet in the galley and head.
In that day problems with onboard electricity, (AC or DC,) were fairly rare, and usually confined to corroded connections and bulb sockets.
Whole different ball game today.
In those days a quality boat, (like you're searching for,) would have bronze fasteners, bronze seacocks, bronze packing gland, bronze stern tube, bronze propellor, bronze prop shaft, bronze rudder shaft, and bronze keel bolts.
AND NOTHING WOULD BE BONDED, NOR WERE ANY ZINCS REQUIRED.
The introduction of stainless, (it's just steel that "Stains Less",) for prop shafts, found the need for sacrificial zincs.
Not to protect the prop, but to protect the stainless shaft which is less noble.
For a wooden boat the survival of its hull depends upon ZERO electrons being able to reach the wood thru any fittings immersed in water, (there are a couple of exceptions). Perhaps I should have underlined or capitalized that last sentence, it's that important.
There are ways to protect people from AC shore power, and protect the boat and its fittings, and that can be discussed "on down the road", depending upon a particular boat you buy, how it's equipped, how it's wired.
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Old 16-08-2022, 19:37   #5
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Re: Isolate Batteries in woody

Quote:
Originally Posted by Hinckley or Die View Post
Where is a good place, in general to put the battery bank?

Some place where the weight works out balance wise and where there's room.


Quote:
Should I build an isolated well vented battery box?

You should be sure the batteries are secured to the boat and that other objects will not contact them or the cabling. The lead acid chemistries require ventilation. Lithium does not. Some sort of nonconductive, fire resistant box is best but most boats don't have that. There are flame retardant grades of fiberglass panel that work really well but they are more expensive than what people usually use (https://www.mcmaster.com/framing/fla...eets-and-bars/)


Quote:

What about cooling?

Allow enough airflow to dissipate 3% per hour of the bank's watt-hour rating. So if you have a 12v bank that's 400 amp hours, that's 4800 watt-hours, 3% is just shy of 150 watts and that's about what they'll dissipate during charging. You should space the batteries so that there is airflow between them.



Quote:

Wiring, is there anything different about wiring a wooden boat as apposed to glass boat?

It's easier to drive a screw for a cable clamp. Otherwise the same.
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Old 16-08-2022, 22:59   #6
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Re: Isolate Batteries in woody

Hello; looks like all the cool kids are following the wooden boat threads.

For location I would start looking around where the existing batteries are, so probably near the engine. Good low center of mass. You could build an enclosure or just purchase some plastic battery boxes with the hardware and strapping to properly secure them. This should keep the water out and the acid in.

As for cooling, Jammer did a lot of great math there, which I appreciate! I'll expand that each Watt is 3.41 btus so to give you an idea what about 500 BTUs mean, it would raise the temperature of the contents of your 8 oz. coffee mug 60 degrees in an hour. So if you think your coffee would cool off that much in that period of time, the batteries will probably be ok. Personal disclaimer; this is bar napkin math.

I don't bond either, except both my DC and my AC (via terminal strips) are connected to the engine foundation which uses the shaft for earth, which has a zinc (stainless). I also have a galvanic isolator between the boat's shore side plug and the AC breaker.
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Old 17-08-2022, 07:13   #7
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Re: Isolate Batteries in woody

Yandina makes the only 2.5 volt Galvanic Isolator Plus which will give you twice the isolation from DC voltage coming from the dock ground. All other isolators are only 1.25 volts. It is rated for 50 amps, fail safe, and unconditional warranty.
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Old 17-08-2022, 15:24   #8
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Re: Isolate Batteries in woody

The ABYC recommendation of connecting the AC ground and the DC ground together, and thence to a bonding system that includes all metal objects, (tanks, seacocks, water heater enclosures, etc.,) and the engine is common practice as a safety measure to protect people.
It's not so great for the protection of a wooden boat.
Stray currant, (AC or DC,) that finds a path to the water thru a fitting will start a reaction in the wood that leads to the "de-lignification" of the wood surrounding that fitting(s).
That's the "white powder" one may have seen on the wood.
Early on, when electrical systems began to flourish, many thought the answer was "add more zincs", WRONG, that just made things worse.
So, we want safety for the people and the boat, (and someone that may be in the water next to the boat).
We'll assume that your shore connection on the dock is protected by a GFCI breaker.
Have an RCD on the inboard side of the shore power fitting.
Every AC outlet should be GFCI protected.
Permanently installed AC devices like a battery charger, water heater, etc., should be hardwired using a GFCI as a "feed thru" device, (I mount them in those weatherproof boxes with the hinged/gasketed cover plates). Then checking/testing/resetting is easy, and regular testing should be part of your program, just like many other things.
Use a "Drivesaver" at the prop/trans coupling, don't let the engine be a "Grand Central Station" that feeds any stray DC into your shaft/prop, the zinc on your stainless shaft is there to protect the shaft from the bronze prop, not to be a dumping ground for DC coming from bad wiring practice.
Further on down the list is keeping AC lines separated from DC.
Example: Your shore power line in within a bundle of DC wires.
The AC line can have a "transformer" effect and induce an AC ripple into the DC wires next to it, batteries in particular really detest any form of AC in the lines coming from a charging source.
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Old 17-08-2022, 17:09   #9
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Re: Isolate Batteries in woody

Bowdrie what's your recommendation on the DC panel, do you not earth the DC or AC at all?

Also, if the first outlet in a circuit series is a GFCI, then that GFCI will protecting the entire circuit (all sub outlets). It saves a lot on GFCI outlets if you don't mind walking back and resetting the one. They also in general have a higher failure rate than a regular outlets (I've had to replace a couple at work, but there's no circuitry to fail on a standard outlet).
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Old 17-08-2022, 18:19   #10
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Re: Isolate Batteries in woody

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Originally Posted by thesaltytar View Post
Bowdrie what's your recommendation on the DC panel, do you not earth the DC or AC at all?
Oh yeah, all the "green" wires from everything are on a bus that goes to the shore power inlet, thence out the cord to the dock.
I don't connect the "green" bus to the DC Ground bus.
With the entire boat basically on 3 GFCI systems in series, Dock, Inlet, Outlet(s), the chances of someone getting shocked are pretty low.
The DC system is just like any other boat, except that it's impossible for any DC to get to the water thru any fitting.
It's a "Floating" DC system, , like a car on rubber tires
Of course, I can't recommend that the ABYC specified connection between AC and DC grounds should not be followed.
The ABYC also does NOT specify that built in appliances, (like water heaters and batt chargers,) are to be wired thru GFCI circuits.
I choose to do so; I believe it's a safer way.
It comes down to two main differences.
1, ABYC wants the green wires to connect to a DC pathway to the water.
2, I want multiple GFI protection, so I don't have to provide a pathway to the water.
It can be argued that the ABYC method is safer in that it does not rely upon any "device" for ultimate protection.
And yes, if all my GFI devices failed in the "on" position then the scenario exists for a shock hazard.
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Old 17-08-2022, 18:40   #11
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Re: Isolate Batteries in woody

I haven't seen a GFCI fail "on" before (not saying it can't happen!). For me they typically fail as an open circuit.
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Old 17-08-2022, 18:53   #12
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Re: Isolate Batteries in woody

I've seen GFCIs fail closed and I've seen the "good" QO circuit breakers fail closed.


The most remarkable thing about electricity is that we don't have more fires.
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Old 17-08-2022, 19:05   #13
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Re: Isolate Batteries in woody

Please, not at all trying to convince anybody of anything.
There is nothing that's "wrong" about the engine being electrically connected to the water via the prop shaft.
If you're not getting any wastage of the prop and the zincs aren't going away quickly that's a good indication that things are ok.
So many boats have all kinds of issues with corrosion, and much of it comes down to the simple stuff, like an aluminum tank sitting in bilge water with a sending unit feeding in the electrons, or a bilge pump switch that's feeding juice thru the bilge water to a keel bolt.
Or how about the shore cord with cracked insulation that's hanging in the water alongside and some of the juice comes back aboard thru a seacock that's bonded.
The list is endless.
We do our best and hope it's good enough.
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Old 18-08-2022, 12:57   #14
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Re: Isolate Batteries in woody

So what I am hearing is that I should obviously keep this as simple as possible. Which I plan to do.

The batteries per the survey are in one of the cockpit lockers (which I am not a fan of), and need some work.

Ya'll have answered a lot of what my questions are. I am just mostly concerned with safety and making sure I don't create an issue because of the conductivity created with water, metal, and wood. I really am trying to grasp complexity of that situation and am probably (it seems) making it more complex than it truly is.

The boat was built in 1959 (as some of you know), and I am uncertain at this stage if it was ever updated. Regardless, there have been much advances in technology in how we try to handle electricity...but electricity it self, has not changed.

Current mission was to be sure I could understand the solutions with bonding and conductivity...Thanks to ya'll I do.
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