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**Dockhead** · 22-12-2009, 08:16

24v is of course much more efficient. You get less voltage drop over your wire runs (assuming the designers did not halve the wire gauge, compared to a 12v system), and high current things like bow thrusters, winches, and windlasses work better and safer.

The downside is that not all equipment, especially electronics, is available in 24v, and sometimes that which is available, is overpriced. Some which is available and not overpriced, is harder to get. In my experience, pumps and bulbs are not a big deal, but electronics will demand a dropper, which introduces additional complexity.

Our boat has 24v house and service systems, but both engine and generator start systems are 12v. So it is somewhat complicated, but on the other hand it's not really bad to have complete separation between house and engine start systems (separate alternators).

On the whole I am glad we have it, but our boat is 54', and as others have said, it makes less sense on smaller boats.

Pelagic · 22-12-2009, 08:22

The choice really is a function of size and complexity and with DC/DC convertor, there is no need to limit yourself to just one.

All my electronics are 12v / all my domestic pumps/ motors / lights / AC inverter-charger / windlass / thruster / starter / …feed off a healthy 24v bank.

botanybay · 22-12-2009, 13:23

An example of the downside...

I have two manual Lewmar 54 series winches which can be upgraded to electric (the 66's are already powered, the old 52's are the old style and can't be upgraded)...

However, there appears to be a complete kit for doing this for 12V but Lewmar says to do the same thing for 24V you have to buy the individual pieces as they don't have a complete kit.

We shall see how much the cost delta is, the 12V upgrade kit is about $3200 USD per winch (I only need to do one side) hopefully the 24V parts are not a huge amount above that.

On the other side, a friends boat which we installed a 12V 2500 watt SW series inverter resulted in being "outside the recommended wire run length for any size wire" (it is a high frequency inverter and thus the DC circuit looks a bit like a transmission line). In the end I designed up a parallel feed which produced a low inductance connection but the run of about 8-9 feet ended up being 4 red pieces of 4/0 wire and 4 black pieces of 4/0 wire!

Wrestling that through the boat was not the easiest thing in the world.

I am just now starting to see some of the equipment for even larger vessels being 48V equipment. (Thrusters, Winches, Inverters, etc) which has the advantage of being common with the telecom market but the higher voltage in the marine environment is a bit of a concern for me...