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Old 19-04-2016, 17:11   #31
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Re: 48v 36v 24v and 12v system

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Chessyman you're close. The thing that decides the a boats DC voltage is the starter motor. If you have 12 volt starters the most practical way to wire your boat is 12 volts.

If you have the choice of 24 volt starters, by all means wire the boat for 24 volts.

If you have the option of higher voltage starters, don't choose them. You won't be able to find the right voltage auxiliary equipment such as bilge pumps and blowers.

Some 32 volt equipment is still available but it will soon disappear from the market.

Yes you can have multiple DC voltages but why bother? It just complicates things.
Actually there are enough 32v shrimp boats that there are plenty of refrigerators, fans, etc for 32v. I don't like 8v batteries, but not much of a stretch, to 36v from 32v. And you can get dc/dc converters cheap as dirt on ebay. A lot of motoryachts were wired for 32v/110v, such as the Hatts. 32v starters are common on '71 series diesels. No, you won't find this stuff at Worst Marine, but a resourceful scavenger/shopper can find all sorts of stuff for various voltages at commercial chandleries geared more toward fishing and workboats. You are right, it is easier to have one battery voltage, but there is really no reason why it has to be 24v or 12v. As 48v electric propulsion systems get more popular, I am predicting (and hoping) that native 48v nav lights, pumps, etc will become more common. I have the old 12v bank and I have my 48v propulsion bank, and I will be getting rid of the 12v bank pretty soon.
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Old 19-04-2016, 17:35   #32
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Re: 48v 36v 24v and 12v system

Quote:
Originally Posted by HopCar View Post
Chessyman you're close. The thing that decides the a boats DC voltage is the starter motor. If you have 12 volt starters the most practical way to wire your boat is 12 volts.

If you have the choice of 24 volt starters, by all means wire the boat for 24 volts.

If you have the option of higher voltage starters, don't choose them. You won't be able to find the right voltage auxiliary equipment such as bilge pumps and blowers.

Some 32 volt equipment is still available but it will soon disappear from the market.

Yes you can have multiple DC voltages but why bother? It just complicates things.
Well, except that starter banks should be completely separated from other DC systems if at all possible, with their own alternators too.

If you manage that, then there's no need to let the starter motor dictate the rest of your system.

The issue is not only the efficient transmission of power around the boat, but also the efficiency of the devices internally. 24v windlasses and bow thrusters are usually more powerful than their 12v analogues.

If you don't have any DC electrical gear on board besides some lighting, instruments, etc., then 12v is fine. But once you get into transporting bulk amounts of power to bow thrusters, windlasses, and -- especially -- inverters, then 24v starts to make a great deal of sense.

32v and 48v is even better, but you will have trouble finding a lot of your DC gear in those voltages. 24v is common enough that you can get most anything in that and avoid droppers.

The Oyster I almost bought was 100% 24v -- the main engine and genset had 24v starters, even though the starting banks were separate from the house bank, with their own alternators. That's the way I would prefer it.

My boat has 24v for house and service, so winches, windlass, thruster, inverter, lighting, radios, etc., but both main engine and generator have 12v starters and their own separate 12v systems, giving in to the greater prevalence of 12v.
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