24 volt system

[emnick]

Is there a reason why boat makers do not use 24 volts instead of 12v? it would in most cases half the thickness of cables required. I appreciate that space may be a problem but most of us have multiple battey banks. I was recently trying to spec new cable for a tricolour and the size for the small lamp was working out to bigger than I thought, and much more expensive. If copper keeps rising it could save alot of money on build cost perhaps

 

[pvb]

Maybe it's because most small leisure diesels are configured as 12v.

 

[savageseadog]

24volts is a superior system in my view, currents are less. I'm on 12 volts myself but that's the way it came.

 

[LadyInBed]

12v kit is more readily available, and mostly cheaper.

 

[saltwater_gypsy]

Correction: a lot of modern kit is in fact rated 10 to 32Volts. Most of the Raymarine chartplotting stuff is rated like this but irritatingly the ST60 kit is 12V. A reasonable system is to have 24V for power applications and a small 12V battery for instruments which can be charged via a 24/12V voltage convertor

 

[William_H]

Yes i understand some modern cars are moving to 50volt.

12v has become historically the standard for cars ad hence it is easy to use for boats. When you are complaining about wire size required just remember that a thicker wire will be more resistant to corrosion so should last longer than the thinner wire you could use in some cases.
olewill

 

[Stoaty]

[ QUOTE ]
12v kit is more readily available, and mostly cheaper.

[/ QUOTE ]

I am 24v and I have never found any problems getting hold of any kit or fittings. I do have a 24 to 12volt converter to a car type socket for charging mobile phones etc. But even those are available in 24v from truck stops.

 

[pvb]

[ QUOTE ]
Yes i understand some modern cars are moving to 50volt.

[/ QUOTE ]The emerging industry standard is 42v, but introduction will be fairly slow.

 

[Piers]

Play d'eau is 24v, with a 12v bus bar for VHF radios etc. There are two droppers (for redundancy) in parallel, either capable of running the bus bar if one was to fail. Furthermore, and to meet the reqirements (whose I don't know - CE mark perhaps?) they charge a separate 12v battery, so if the 24v fails, the battery will keep the bus running.

 

[Andrew_Fanner]

Jedi is 24V which does have the advantage that the current eaten by the flash electric fridge is kept low. The 12V system is a bit rubbish by comparison as it runs by centre tapping one battery pair and I have a vague feeling this is undesirable. I have never fitted a dropper instead, guess the best idea would be a 24-12 dropper/charger and separate 12V service battery?

Silly Q, is a dropper more sophisticated than a big resistance? I assume it must be.

 

[rickp]

I have a similar setup to Piers - though I have a gang of 3 DC-DC converters which switch off with the 'master off' switch along with one to provide power for the devices that want it 24x7 (car radio memory, Navtex etc).

It also makes the halogen bulbs last much longer when run (and dimmed) from a nice stable 12v supply.

Rick

 

[Piers]

Hi Andrew,

In answer to [ QUOTE ]
Silly Q, is a dropper more sophisticated than a big resistance? I assume it must be

[/ QUOTE ]

Yes.

 

[LadyInBed]

I was thinking more VHF (car) radio, Alternator, Internal light fittings, dingy inflator, phone charger etc, etc.
I also have a duel 24 & 12v system but they are isolated from and independent of each other (2 alternators) so if a system /battery fails, it's not the end of electricary as we know it /forums/images/graemlins/wink.gif
I do have one common point - a 24v wind gen which also tops up the 12v system via a 24/12 converter / charger.

 

[Gumpy]

Parglena is 24v for the domestics. The engine start and navigation lights/vhf etc are all 12v and run off their own batteries as they were cheaper than 24v when I bought them.
However I have two alternators one for each voltage and no droppers.

One thing, Dont ever run any 12v equipment off half of a 24v system its a sure way to ruin your batteries.

Julian

 

[Piers]

Lady in Red makes a very good point. Don't take a 12v supply from a battery bank wired for 24v.

 

[Andrew_Fanner]

[ QUOTE ]
Lady in Red makes a very good point. Don't take a 12v supply from a battery bank wired for 24v.

[/ QUOTE ]

I suspected as much. This moves to the jobs list before the season starts. I reckon a 24-12 dropper from each 24V pair to feed two 12V service batteries will be ample, in fact one 12V might suffice after I've done the sums on Ah use. Rats, that's added a rewire to rebuilding the galley

 

[ccscott49]

Englander is 24v, I also have 24-12 droppers for my minimal 12v gear, supplied by domestic bank, engine start is totally seperate.
Never centre tap a 24v system to provide 12v!
The genny is 12v start, but has two seperate batteries for it, I dont use that supply for anything but genny start, safer that way.

 

[halcyon]

Be careful supplying a 12 volt bank via dropper from a 24 volt bank, it works, but watch over voltage. When not supplying any 12 volt system loads, the off load voltage can be high with battery connected.

We did a system on a boat a few years back and we getting a good charge voltage, so I fitted a controller to stop over charge. This also allowed it to be connected all the time, avoiding the need to switch it off and on.

Brian

 

[Piers]

The way I did it on Play d'eau was to have 2 Mastervolt droppers (DC/DC Converters; Type MAC 24/12-20A; Part no. 081200100 - two for failure/redundancy) which also keep a 12v battery charged (12v sealed AGM Lifeline 12v 105AH GPL-31T).

So, if the 24v supply fails, there is resource in the battery to keep the 12v bus alive for a considerable time.