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Old 21-10-2010, 09:03   #1
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Circuit Diagram 46' Cat

I am putting together a 12V system for my cat rebuild. To give some idea of my electrical abilities, the last time I rewired a boat I used lamp cord and wire nuts. In an attempt to clean up my act and atone for past sins I read some texts and came up with the attached diagram. I thought I would post it here so that any glaring faults could be exposed before I set fire to my boat.

As the diagram shows, there will be a 450A house bank, charged mainly by solar and wind with alternators as backup. House loads in the hulls will be carried by 2 large guage wires with fuse blocks along their length and switched at the device.

Any comments, especially in regard to circuit protection and grounding, would be greatly appreciated.

Thanks,
Mike
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Old 21-10-2010, 09:20   #2
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Tip 1. Use only marine grade tinned copper wire for your re-wire
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Old 21-10-2010, 22:29   #3
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If your battery bank is in one hull, your problem is going to be the thickness of the wires connecting it to the other hull, including the engine in that other hull.
We also have a 46ft cat and have split the house battery in 2 halves (400AH each), each in one hull and connected directly to the engine next to it. We still have to run good size wires between the 2 half banks, but at least, each engine is connected as it's supposed to be. We don't have a special regulator (probably should have 2) and rely on the original Yanmar integrated regulators. Most of our energy, like yours, comes from solar panels and a wind generator.
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Old 22-10-2010, 08:19   #4
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Quote:
Originally Posted by claire View Post
If your battery bank is in one hull, your problem is going to be the thickness of the wires connecting it to the other hull, including the engine in that other hull.
Yes indeed. This was the topic of a previous thread that I posted, wondering if builders were using very large cables or just accepting a greater voltage drop with smaller cables.
Battery Cable Size on Larger Cats
The batteries will be on the port side of the saloon. If I use 2/0 cable to the stbd hull the voltage loss is 4.6%. If I use 4/0 this is decreased to below 3%. I thought of splitting the house bank but in the end decided to go with the single bank configuration to avoid large depth of discharge percentages and to keep things simple.

Mike
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Old 22-10-2010, 08:22   #5
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Have you considered a distributed power system; aka "Three Wire Boat"?

Charlie
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Old 22-10-2010, 08:23   #6
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Tip 1. Use only marine grade tinned copper wire for your re-wire
Fortunately for me they don't make 4/0 lamp cord, but that doesn't mean I won't stop looking.
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Old 22-10-2010, 17:55   #7
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Have you considered a distributed power system; aka "Three Wire Boat"?

Charlie
Charlie,

I did look closely at the Capi2 system but in the end it is well out of my budget. I have tried to realize some of the benefits of a distributed system by using a "fuse-block" based system for switched loads with no remote switching.

Mike
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Old 22-10-2010, 19:29   #8
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Mike,

I read the other thread and can give you the answer to one question: Fountaine Pajot apparently installed 2/0 wire on our 46ft cat., it seems they have a "Sunsail version" of the electrical installation that we inherited when we bought the boat. It had only one small house battery on the starboard side.
We have since significantly modified the setup as per the attached circuit diagram. It is simple and works to our satisfaction, while reusing most of the pre-existing inside distribution.
We have only one engine battery for the starboard engine. The switch is there to add one for the port engine but in 5 years of cruising full time, we have never needed to use the engine battery and always start with the house battery (the engine battery is kept in good charge by the battery charger during occasional marina stays).
Regarding wire thickness, we have 9m wire between the 2 house battery banks. The original wires are 2/0 and I have doubled the ground connection with a 1/0 wire.
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