Switching from 12V to 24V

[lituya1617]

I have seen commercial fishermen try to make 24 volt systems work with 12 volt systems and the results have been chaos and cursing. While higher voltages allow higher power density in starters (the primary place 24 volts is used) thrusters, anchor wenches and other high amp draw services with about half the size of copper wires, this advantage is of little real world advantage. 12 volts works just fine in all these applications. I would advise against having a dual voltage DC system because complexity is inversely proportional to reliability.

[john61ct]

Anchor wench, hehe

[exMaggieDrum]

I have found shops that specialize in rebuilding alternators and starters to be invaluable resources for all questions about them, so long as it is a reputable vendor which does a significant amount of business. A lot of shops that "rebuild" these actually just send them out to a rebuilding shop.



Just a thought regarding getting some professional advice on voltages for starters. I can't say that they would get this question often but if anyone does they would. Most of their business would be trucks/cars but the one I use does a big business for boats as the Pacific Northwest is boat intensive, both commercial and recreational.


I am surprised how much this thread has taken on the aura of a "which anchor, type of boat, religion, battery" discussion.

[kapnd]

Originally Posted by sailing_jack

One point of concern regarding cheap dc to dc converters.
They all have a high frequency oscillator to do the conversion, either by pulse width modulation or a high frequency transformer.

Cheap Chinese (and maybe other low cost suppliers) often take shortcuts with shielding. If you are wondering why your HF or VHF radio is noisy, try turning off the converters.

It is as always, Buyer Beware !

This may be true, but on my vessel would be hard to prove, as my VHF is one of the few items onboard that requires 12 the volts!
The radio works fine on a Mastervolt 24/12 v converter, not noticeably noisy.
however the 20anps available dwindle quickly as I run some fishing gear on 12 v, and will likely need to upgrade 12 v power in the future.
I will likely will do so with a 12 v bank and a 24/12 charger, to avoid installing a 12 v alternator.
Heavy 12 v use is only occasional, and won’t justify the expense of alternator installation.
This thread has been a pertinent read for me, thank you all for your contributions.

[guitarrich]

I can’t believe a 12v starter motor will be happy with 24v, but I would expect a competent auto-electrician could re-wind it for you to work on 24v.
24v systems tend to be safer and more reliable than 12v. Current (the killer) is halved. Wires can be smaller gauge, reducing cost and weight. As to the fans etc, do a quick sum for the total demand, then obtain a voltage dropper. There is a wide range to choose from, and they are relatively inexpensive.

[coopec43]

[I]I can’t believe a 12v starter motor will be happy with 24v, but I would expect a competent auto-electrician could re-wind it for you to work on 24v.[/I]

Do you have a technical reason for believing that? If the auto-elect rewound it would it be with lighter or heavier wiring?

As for oscillating fans have you checked out the price around AUD25 each?

Clive

[guyrj33]

It’s a DC motor, it will be fine at 24v.

[coopec43]

Originally Posted by guyrj33

It’s a DC motor, it will be fine at 24v.

It's not as if you'd be churning on the starter for 40 or 50 seconds (although some people would be stupid enough to do that).

Clive

[coopec43]

https://www.youtube.com/watch?v=rXndrYdMduM

[coopec43]

Published on Jul 8, 2012
The owner of this nice Suzuki Samurai upgraded his champion 9500TDS winch.
air controlled clutch, for quick free spooling.
and a 24volt powerbox, normal winching at 12 volt, and 2x faster at 24volt.
Extremely nice upgrade for the TDS winch, which does 18m per min @ 12v.
now @ 36m per min, faster then any warn winch which still costs 2 times more than this winch with upgrade

[TonyDove]

From all of the above I tend to the view that 24V is generally 'better' … for all the reasons stated above. In particular, on sailboats, power wires up the mast can be lighter gauge … so less weight aloft … which is always a good thing.

So if I were outfitting a new boat I'd specify 24V for everything that can be 24V … which is most things. However, I haven't found many (any?) VHF or SSB units that aren't 12V … and NMEA2000 power is 12V. So it would seem that there is going to have to be a 12V circuit in the mix. Even if I had an exclusively 12V system … I would have the VHF and SSB on a separate battery anyway … you don't want to be without communication if somehow the house battery bank gets run flat.

Dual voltage systems wouldn't seem to be beyond the ability of most people to cope with … provided they are well separated and label label label those +ve wires.

Happy sailing

[CatNewBee]

you can use step-down converter for the 12V stuff, if the loads are not to big,
so powering the N2K bus is no problem. Also the VHF and the chart plotter can be powered that way, I am not sure about the radar, it takes more power, maybe you'll need than a larger DC/DC converter there, but if you place it strategically near the plotter/VHF radio and feed the N2K bus from there, you'll have very little 12V wiring.

You probably will have to replace all LED modules / stripes / bulbs for the lights inside with 24V equivalents too.

[coopec43]

Originally Posted by coopec43

Originally Posted by TonyDove

So if I were outfitting a new boat I'd specify 24V for everything that can be 24V … which is most things. However, I haven't found many (any?) VHF or SSB units that aren't 12V … and NMEA2000 power is 12V. So it would seem that there is going to have to be a 12V circuit in the mix. Even if I had an exclusively 12V system … I would have the VHF and SSB on a separate battery anyway … you don't want to be without communication if somehow the house battery bank gets run flat.

Happy sailing

Tony I have been trying to prove you wrong re the scarcity of 24V SSB, VHF UHF radios.

I searched for 24V and didn't find any.
I searched for 12V and didn't find any (but there were plenty of 13.8V....)
(Most advertisements don't even mention power requirements)

Then I found "ICOM IC-450 80 CH UHF CB TWO WAY RADIO 80 CHANNELS IN VEHICLE LCD SCREEN 12/24V

• 5 Watts (High) and 1 Watt (Low) Selectable Output Power
• 80 CB Channels plus up to 35 receive only Channels
• Noise Cancelling Microphone Icom
• Voice Recorder allowing up to 10 messages recorded with a total recording time of 5 minutes (30 seconds per message)
• Built-in Speaker
• 12 or 24 Volt automatically detected
• Voice Guidance which announces channel type and number
• Small and compact for installation
• Main unit can be mounted out of sight
• New design, compact control speaker microphone with newly designed user interface and menu structure

I'll keep looking.

Thanks

Clive

[john61ct]

12V is just a nominal label, means higher IRL.

Most devices will tolerate a wide variation.

Charging can go to ~15V

[rgleason]

24vdc is tantalizing:


12VDC Loads

• Masthead Tricolor Optolamp Amazonia Mirim Power source: 10,6V to 14,4V.
• All cabin light are 11-16vdc LED
• Standard Eclipes VHF/DSC Power source: 11Vdc to 16Vdc.
• N2k bus Some instruments may be 10-15vdc
• Raymarine Instruments ST60 10-15vdc
• Raymarine Autopilot Wheelpilot 4000 - 10-15vdc
• Computer Our adapters are for 12vdc
• Search light & Phones, USB etc.
• Other devices

24VC Loads

• B&G Zeus12 Touch: 9-31.2vdc for chartplotter
• B&G 4G Radar: 9V to 31.2Vdc (12/24 Volt systems), Operating18W@3.8Vdc & Standby: 2W@13.8Vdc ~ 150mA (Typical)
• Maretron N2K bus: Between 9-32 volts, but some devices are 9-16 so check each N2K device!
• Starter - I am convinced it would be ok now, thank you coopec43
• Alternator - new.
• Ozifridge - Danfoss compressor is ok, control need a small 24vdc/12vdc converter.

120VAC Loads

• Domestic Water heater - Rewire plug to 120vac or adapter from 230. This is a resistance coil.
• Ozifridge Rewire 230 plug or get an adapter to 12vac.

So it looks like there would need to be a House Panel 24vdc/12vdc converter and possibly a 12vdc battery for navigation and nav lights and talso emergency starting.



The question for us boils down to do we really need to have a 12vdc panel and a 24vdc panel? We don't have room for it really and it will be a more complex system. We also would not gain much in the way of wiring, since most of it is already wired. So why not stick with with House 12VDC Panel and devices (Lock stock and barrel)?


Then have the heavy load, the starter (for us), the alternator, the LiFePo4 batteries and the Solar be 24vdc? If there are other heavy load things added like a windlass or watermaker, they could be 24vdc with a small panel added somewhere.