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Old 16-01-2016, 16:02   #1
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12 volt re-wire

My sail boat is only 10 yrs old, steel construction. A friend did the wiring initially, another friend did a bit more, another said he could tweak a few things. Bottom line is that something is draining the batteries completely and has been for 3 years (made seasonally tolerable only when there is sun for solar panels). Winter here is when it happens. Now I want to start from scratch and re-do the whole dam mess. Would appreciate a book recommend or something on line for just basic 12 volt setup. My boat is basics... no refrideration, tvs, etc... nada... just lights and panel for running lights, radar, shore power. I have a cranking battery and 2 deep cell house bank.
thanks in advance...

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Old 17-01-2016, 19:31   #2
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Re: 12 volt re-wire

One thing to remember is a steel boat is NOT like a car. I had a steel boat and the PO just grounded wires to the hull causing no end of problems. Do not ground to hull. Check
For boat electric. Get several different ones.

That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.
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Old 17-01-2016, 19:42   #3
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Re: 12 volt re-wire

I have a power drain as well. I finally determined it was the battery combiner's solenoid. One of its sense wires was off, causing it to try to combine always. Better to find the leak before a big re-do.
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Old 17-01-2016, 21:35   #4
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Re: 12 volt re-wire

Nigel Calders book is my go to and my recommendation.
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Old 18-01-2016, 04:01   #5
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Re: 12 volt re-wire

Originally Posted by Nicholson58 View Post
I have a power drain as well. I finally determined it was the battery combiner's solenoid. One of its sense wires was off, causing it to try to combine always. Better to find the leak before a big re-do.
100%, but it is worth familiarizing yourself with the wiring in your boat. Finding the problem will give you infinitely more confidence in your abilities and will show you where deficiencies exist in your systems. If the work was done by volunteers for no remuneration you might be surprised with what you find. Even many tradesmen cut corners when doing this type of work.

My only other recommendation is if you do make changes or rewire rip out the old stuff being replaced or upgraded. There is nothing worse than having to deal with redundant wiring in a boat.
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Old 18-01-2016, 04:14   #6
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12 volt re-wire

Another Nigel Calder vote from me. And if in doubt, rip it out and start again.

Actually, that's a bit easy to say, and with such a young boat I guess it is worth seeing if you can find the source of the problem, but simplify, simplify, simplify at every opportunity.

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Old 18-01-2016, 07:56   #7
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Re: 12 volt re-wire

I worked in a mid-sized boat yard for five years and sailed and be there and done that (and have SO much to learn still). I had Calder's first book, and his second (the big everything books). I found Nigel to be hard to read and to put together his good advice. If I need something very specific I go there. If I were designing a new system I would only go there after I read some of the other electrical system primers. I don't have the list but there have been several threads in just the last few months on this exact topic. Not on metal boats specifically but what you need to start. Very little different except you don't want to make the hull part of you electrical system. You have to isolate the engine, etc. etc.

If you want to track down a parasitic draw get a clamp on ammeter. It will enable you to track down stray currents if you are careful and methodical. If you hired an electrician that is what they would do. I'd start by turning off all your breakers, remove shore power plug, and start at the batteries and look for any current flows.

Then you go from there to find the large then small wires where the current goes. If you don't find anything there turn on one breaker at a time, with all the uses of that circuit OFF. E.g. lights, electronics. At that point you can start with tracing the smaller circuits at the panel and out.

And don't forget all the cables that go to circuits not on your panel - alternators (are a frequent parasitic draw), windlass, chargers, etc. etc. Make sketches of all! And keep them! You need to do the sketches and identify all your charging sources and uses BEFORE you start rewiring. At least I would. You can just do one circuit at a time or start with the big stuff and do that first. If I were doing a complete rewire (I am on my boat) I would start there first anyway. You may decide you don't need to redo all the big stuff.

I have been on so many boats with electrical messes. It makes me sick to see them. They often start like yours does and get worse with all the amateur "help" you get from well-meaning friends.

Good luck with it all. But do some research on here and find the previous threads. They have some good tips and will give you an idea of what you are facing. It won't be cheap. Use marine grade tinned wire - only. And fuse everything.
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Old 21-01-2016, 19:55   #8
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Re: 12 volt re-wire

+1 on exMaggieDrum advice. tracing and finding the problem, and producing good drawings as you go, will give you confidence and knowledge.

If you could only own ONE book, I'd vote for Calder also, but if you're fairly new to electrics and 12v systems, you might get more right now from a good basic boat electrics book.

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