Surboum
Veteran Member
I’m currently looking at a boat that has a 24-volt system. All my previous boats have had 12-volt systems. That got me wondering what the advantages, disadvantages, and trade-offs are for a 24-volt system vs. a 12-volt system?
24-volt vs. 12-volt
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C lectric
Guru
24 volts can convey the same amount of power with wire that is MUCH smaller. Smaller wire means less weight and expense, less copper and labour, which is becoming very important in the newer boats where people MUST have everything and the power loads keep going up.
Small voltage drops can be tolerated better than in a 12V system. Not totally tolerated as all should be done to keep to a minimum.
24V can mean the difference between special battery sets in various locations for thrusters, windlasses, and the like vs one big set in a central location.
Many larger older boats with big engines used combination V supplies. 12V for normal house loads other than generator supplied, and 24V for the engine starting using several relays. This can be reduced/eliminated if the whole boat is 24V. My own engine, now 43 yrs old , could have had a 24V starter but with some, for me , headaches.
There is a catch for now which will slowly be reduced, much equipment is built for 12V only. More will come on line built for either 12 or 24V without any other changes so over some more time the equipment will/is becoming dual voltage.
If your boat has 12 V it is not worth redoing.
Small voltage drops can be tolerated better than in a 12V system. Not totally tolerated as all should be done to keep to a minimum.
24V can mean the difference between special battery sets in various locations for thrusters, windlasses, and the like vs one big set in a central location.
Many larger older boats with big engines used combination V supplies. 12V for normal house loads other than generator supplied, and 24V for the engine starting using several relays. This can be reduced/eliminated if the whole boat is 24V. My own engine, now 43 yrs old , could have had a 24V starter but with some, for me , headaches.
There is a catch for now which will slowly be reduced, much equipment is built for 12V only. More will come on line built for either 12 or 24V without any other changes so over some more time the equipment will/is becoming dual voltage.
If your boat has 12 V it is not worth redoing.
GoneFarrell
Guru
I've got 24V starting bank and a 12V house bank, works fine. They are separate systems/alternators/dockside chargers, joined only at the ground side.
If starter bank dies I can move the jumpers from the house bank to push 24V to the starter circuit, or wait for the 120VAC genny to bring back the starter bank.
If starter bank dies I can move the jumpers from the house bank to push 24V to the starter circuit, or wait for the 120VAC genny to bring back the starter bank.
Hippocampus
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If I was spec’ing again as a new build it would be 24V. The US is a bit backwards. We have more 12V boats and fewer 24V than the Europeans.
markpierce
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See no disadvantage with my boat's 24-volt system which supplies most systems such as bow thruster. !2-volts are also produced for some systems such as radio and navigation lights.
AlanT
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My current boat is my first with 24v. As noted by C Lectric there are many advantages to using 24v. For most boats you will also have a 12v supply for (at a minimum) Navigation instruments. This can be accomplished in several ways. On my boat it was a 12v tap off the 24v house supply. This is problematic as it results in differential draw down of the house bank. We added a separate 12v battery and a 24v to 12vDC charger to handle the 12v loads on the advice of our electrician. ~A
kapnd
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I have no gripe about my boats 24 v system.
I have added a 24-12 converter for the one radio that needs 12v, and a phone charger usb.
An added benefit is that most solar systems are 24v, so easy to pair up.
I have added a 24-12 converter for the one radio that needs 12v, and a phone charger usb.
An added benefit is that most solar systems are 24v, so easy to pair up.
HopCar
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If I were buying a boat over about 35 feet I would want a 24 volt system. The distance between the batteries and heavy power users like bow thrusters can get pretty long.
Some years ago it was harder to find 24V equipment but now every thing you’ll need is made in 24V.
32 volt systems used to be quite common. I have even seen 110 volt DC equipment. I have a 6 Volt bilge pump from the 1950’s.
Some years ago it was harder to find 24V equipment but now every thing you’ll need is made in 24V.
32 volt systems used to be quite common. I have even seen 110 volt DC equipment. I have a 6 Volt bilge pump from the 1950’s.
MYTraveler
Guru
In that regard, if you intend to take your boat to remote areas, you are more likely to find 12v replacements, off the shelf, than 24. Ostensibly for that reason, the builders of my boat configured most systems, including main engine starting motors, as 12v, but still 24v thruster and windlass.
caltexflanc
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24 volt is extremely common for marine use items. Way back on '07, all of our extensive electronics,plus the bow thruster, the washdown pump, the inverter bank all were 24 volt. The OEM "house" on the old Hatt was 32v; we had a couple of NewMar 32-12 converters for things that came from land like the flying bridge stereo, a couple of CLAs which in turn ran some car chargers and a bluetooth GPS receiver. We had about every flavor of voltage, including 6, 8, and 12 volt batteries, feeding 12, 24, and 32 volt DC devices, plus 12 (yes, 12), 120, and 240 VAC. Time goes on and things evolve....
HopCar
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There is some discussion of the automotive industry switching to 48 volts. If that happens I wouldn’t be surprised if the marine industry followed suit.
tiltrider1
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More than just a discussion but we will see if ends up on more than just the electric cars.
24v is superior to 12v in every way except that 12v is more common(which often means cheaper). 24v motors last longer than 12v motors.
If you are old enough you will remember 6v cars.
Portage_Bay
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Many years ago I took care of a boat with twin Chrysler Crowns. The were 6 volt system. When everything was on top condition the engines cranked so slowly I never thought they would start. But they did.
One old dock rat tried to get me to put in 8 volt batteries and crank the voltage regulator up. He said they'd spin right up on 8 volts.
I never did. It wasn't my boat.
One old dock rat tried to get me to put in 8 volt batteries and crank the voltage regulator up. He said they'd spin right up on 8 volts.
I never did. It wasn't my boat.
FF
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The usual is a modern 24V engine , and common 12v for most of the rest of the boat.
This is easy to do by installing a Vanner equalizer , which can reliably , produce 60-80A of 12 DC.
These have been made for decades so a used unit is easy.
They do not harm the batts as first one 12v batt is discharged for a very short time then the other.
The windlass or bow thruster can be fed with the 24v .
Since the 60's the car mfg have been talking of 24v cars , thinner lighter everything , but have never got to it.
This is easy to do by installing a Vanner equalizer , which can reliably , produce 60-80A of 12 DC.
These have been made for decades so a used unit is easy.
They do not harm the batts as first one 12v batt is discharged for a very short time then the other.
The windlass or bow thruster can be fed with the 24v .
Since the 60's the car mfg have been talking of 24v cars , thinner lighter everything , but have never got to it.
My boat is 24V. There's some outdated information in this thread. The only things on my boat that still NEED 12V are the NMEA 2000 bus and the cigarette lighter outlet.
Virtually all modern electronics will work on 12V or 24V autosensing.
Navigation lights (and bulbs) are available in 12V or 24V. Most of the LED navigation lights are dual voltage.
Most interior lights and dimmers (LED or incandescent) are available in multiple voltage or auto voltage.
The only downside is you will need multiple batteries to get to 24V. But just about every boat on here has at least two batteries.
Virtually all modern electronics will work on 12V or 24V autosensing.
Navigation lights (and bulbs) are available in 12V or 24V. Most of the LED navigation lights are dual voltage.
Most interior lights and dimmers (LED or incandescent) are available in multiple voltage or auto voltage.
The only downside is you will need multiple batteries to get to 24V. But just about every boat on here has at least two batteries.
Iggy
Guru
Some MFDs today like Simrad and Garmin can use 10 to 32 volts D.C.
That also incudes some lighting. https://www.defender.com/product.jsp?id=6178764
I install a Siren Pro 3 and that the same way. 10- 32v D.C.
Your just going to need some rewiring to separate the two systems.
That also incudes some lighting. https://www.defender.com/product.jsp?id=6178764
I install a Siren Pro 3 and that the same way. 10- 32v D.C.
Your just going to need some rewiring to separate the two systems.
Last edited:
Impulsive19
Member
While your at it - please advise the best way to charge a 24volt bank. Either two 12 volt batteries or 4 six volt
Thanks !
Thanks !
FF
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"Either two 12 volt batteries or 4 six volt."
The battery selection would be made by weather the batts are just for starting or are also the house supply.
If for the house 4 six volt DEEP CYCLE are a low cost solution.
12V AGM also work but are more costly , but can work as start batts too
The battery selection would be made by weather the batts are just for starting or are also the house supply.
If for the house 4 six volt DEEP CYCLE are a low cost solution.
12V AGM also work but are more costly , but can work as start batts too
klee wyck
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I am not very qualified on the subject, but really like my 24V boat. LIBRA runs the house on a bank of 2 volt industrial cells to form a 24 volt system charged by a Victron 24/100 charger.
The house bank seems untouchable during my cruising. It is unusual to see SOC under 90% after 8-9 hours of cruise without the generator running while operating 2 refrigerators, a freezer, and a fair bit of comnav equipment. The 50Amp alternator on the main only serves the starts. If I run the generator during the last 20-30 minutes of the cruise, I am topped up. Seems like a beast.
Rolls makes them, mine are Dutch.
https://www.invertersupply.com/inde...x2NM5SODVTIN-VNBMS1_wr42SZgBcwzwaAqrvEALw_wcB
The house bank seems untouchable during my cruising. It is unusual to see SOC under 90% after 8-9 hours of cruise without the generator running while operating 2 refrigerators, a freezer, and a fair bit of comnav equipment. The 50Amp alternator on the main only serves the starts. If I run the generator during the last 20-30 minutes of the cruise, I am topped up. Seems like a beast.
Rolls makes them, mine are Dutch.
https://www.invertersupply.com/inde...x2NM5SODVTIN-VNBMS1_wr42SZgBcwzwaAqrvEALw_wcB
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Iggy
Guru
I looked up B&G VHF. It's only 12V and I was a little surprised by that. My 3 Simrad unit (same parent co. as B&G) and Fusion can use both.
diver dave
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Hard to find some COMM equipment that is dual voltage. All my SSB equipment is 12V only, including ICOM marine ssb, and vhf. Its much easier to make receivers wide voltage than transmitters. Although, technically, 24, 36 even 48V makes for more efficient high power transmitters and invertors. My airband ICOM transceiver is 12/24v auto range.
Personally I have found every piece of bridge electronics accepts 24VDC except for the VHF radios. I've used ICOM and Lawrence in the past but they were only 12V. However, I'll research Iggy's suggestions. It would be a nice convenience for the boat's entire DC system to be uniform and not having to run a B2B on the bridge battery.
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