12v to 24v conversion

[longjonsilver]

i am considering the purchase of a 1980 Hughes 38 sailboat with old or mostly non-existant electronics. i am considering the rewiring of the boat to 24 volt, and am pleased to find that most new electronics as well as electric windlasses and LEDs work fine on 24v. i also find that starters and alternators are available for Yanmar engines.

What things should i consider as i plan this changeover?

thanks
jon

[brianlara 3]

If you use the correct AWG wire size there are not sufficient gains to be had in changing to 24vdc.
12 volts has more than enough grunt to send current from one end of a 38 footer to the other.
Nothing to stop you doing it but the headaches involved in getting all new 24v capable gear makes it , imho, just not worth it, especially as led lights eg require very little power, and voltage is not power. You need voltage to push current (watts) long distances
Wondering why you see the need.
Others, more expert than me may disagree and I certainly wont argue the point. (I admittedly am a better mechanic than auto electrician).
Do more research is my advice

[sy_gilana]

We are a 24v Boat.

Look in the back of Marine stores for bargains as sometimes a 24v item might sit for years on the shelf, and be cheaper than a faster moving 12v item. Eg. We bought 2 electric heads for $150.00 each.

The wiring is already oversized = good.

Bilge pumps, shower pumps etc, just put the 12v version in, they love the low amperage and pump like crazy.

Watch out for some "24v" led lights that will die when you charge to 30v.

Design around a LiFePo4 battery.

24v Solar panels are cheaper, and rig them in series to 48v before the controller.

Don't look back!

[longjonsilver]

My answers and questions in red.

Originally Posted by sy_gilana

We are a 24v Boat.

The wiring is already oversized = good. Thats what started me thinking about doing this.

Bilge pumps, shower pumps etc, just put the 12v version in, they love the low amperage and pump like crazy. Thats good to know, THANKS

Watch out for some "24v" led lights that will die when you charge to 30v.Thanks

Design around a LiFePo4 battery.Why? Can't i just wire 4 6v golfcart batteries in series?

24v Solar panels are cheaper, and rig them in series to 48v before the controller.Thats good to know too, but what about 30v solar panels?

Don't look back!

How did you deal with the engine alternator and starter?

thanks again
jon

[barnakiel]

Few inexpensive boat electronics exist in 24V version, in some parts of the world (I think). 24V seems more commercial stuff - for fishers, cargoes, etc.

All the less expensive VHFs, AISs, etc. instruments I have seen were in 12V system. I have also seen fewer 24V LED panels and such likes.

Maybe this is country specific, we are in the EC, mostly.

I would stick with 12V unless heavy gauge equipment (big windlass, big bowthruster) are an issue.

b.

[longjonsilver]

Originally Posted by barnakiel

I would stick with 12V unless heavy gauge equipment (big windlass, big bowthruster) are an issue.

b.

Well thats the beginning of my journey into 24v. i believe in having heavy ground tackle, anchoring out rather than a slip and its monthly drain on the budget, and that needs a powerful electric anchor windlass (Lofrans Tigre) that draws 1500 watt, and is available in 12v or 24v versions. Now a 12v version would draw 125 amps, while a 24v version would draw only half that or 62.5 amps. From the battery bank to the windlass would be about 60ft round trip, making for a huge loss of power especially with 12v. This would require 1 gauge wire for 10% voltage drop. Imagine the terminal ends for that! Might as well use welding cable.

So what to do? Have a second battery bank forward? Well, that would make about 20' round trip and require 4 gauge wire for a 10% voltage drop, which is the wire gauge needed for a 24v system, 60' run, 10% drop.

Or convert the boat to 24v. Modern electronics (Simrad 4G radar, chartplotter, sonor, and Icom SSB) all are dual voltage units, (if i understand it correctly), LEDs to retrofit the interior lights, VHF radio, refrigeration and solar panels are available in 24v versions.

So whats left? Engine starter, alternator, engine gauges, nav lights(?), stereo, bilge pump. It looks like 24v alternators are available at reasonable prices and could be made to work with a little fabbing of brackets.

So why not tap off the middle of the four 6v batteries to get 12v and the ends to get 24v and run two systems? Especially since the charging system (both engine and solar) would charge all four batteries at 24v.

Consider the problem of the terminal ends of the wires, that often are affected by corrosion, raising the resistance resulting in fires due to excessive heat loss. 24v, using the old 12v wires, would have 1/2 the current flow, and since Powerlost=I2*R, there would only be 1/4 the current lost at these terminal ends, resulting in a safer boat due to vastly less heating of the terminal ends. What am i missing here?

jon

[pcmm]

Originally Posted by longjonsilver

Well thats the beginning of my journey into 24v. i believe in having heavy ground tackle, anchoring out rather than a slip and its monthly drain on the budget, and that needs a powerful electric anchor windlass (Lofrans Tigre) that draws 1500 watt, and is available in 12v or 24v versions. Now a 12v version would draw 125 amps, while a 24v version would draw only half that or 62.5 amps. From the battery bank to the windlass would be about 60ft round trip, making for a huge loss of power especially with 12v. This would require 1 gauge wire for 10% voltage drop. Imagine the terminal ends for that! Might as well use welding cable.

jon

That's exactly what I did for my boat. round trip for the windlass is approx 65ft with a Maxwell Nissen 1000 watt. But I used 1/0 AWG welding wire (I know its not correct) but the welding wire is run pretty simply and cost 1/4 of the ancor stuff so if I have to change it out in 5-10 years, then so be it. 24v stuff just means that you are going to have to search for EVERYTHING! its much less common than 12v stuff. with LED lighting most of the already installed wire in your boat will be oversized! I rewired my boad for LED and even with 3% voltage drop i haven't needed to use anything over 16awg. saves money time and weight!

[barnakiel]

OK. I see your point.

I would act the opposite way. Place a dedicated winch (/bowthruster, etc) battery close to the winch.

Winch and bowthruster loads are momentary and with very short wire runs you end up with smaller gauge wires. Recharging is always a longer process so any wires do.

But the other way round also works. Just personal preferences in skinning the cat.

BTW I never build 24V banks out of 6V cells. I always build 12V banks out of 12V cells. I am aware of the US preferences and I also work on a ("big") boat where the 24 system is built out of 6V Trojans. This is what there is and I understand why. But this is not what I would build/have in my own boat.

b.

[Buckanear Bill]

I don't understand why we stick to 12V systems. 24V would be so much more efficient, maybe even safer. Amperage draw would be about half, and power loss, which shows up as heat in the wires and connections, would be about 1/4 the loss with 12V. Note that cars once had 6V systems, until it was noticed that 12V provided better lighting. Some industries are settling on 48V, but I dare not mention that!
As longjohnsilver pointed out, 125 A to the windlass is - my words - insane. Wouldn't a shock load like that to the batteries be detrimental to battery life?

[Cadence]

You may be biting off more than you can chew?

[a64pilot]

Originally Posted by Buckanear Bill

I don't understand why we stick to 12V systems. 24V would be so much more efficient, maybe even safer. Amperage draw would be about half, and power loss, which shows up as heat in the wires and connections, would be about 1/4 the loss with 12V.

Why stop at 24V? Cars were supposed to go to 42 V in the 90's, yet are still 12V?

https://en.wikipedia.org/wiki/42-volt_electrical_system

I bet your 12VDC starter will be just fine on 48V also, but your going to need a new alt and regulator and of course chargers. Many, many Ford tractors were converted to 12VDC from 6VDC 40 or 50 years ago and the starters are fine.

You can do it, it will cost a bunch of money and only you can determine if its worth it or not, my vote is no, but I'm cheap.

[Buckanear Bill]

I dunno about 48V into a starter designed for 12V! That's shoving a lot of power into that starter. Think Luke Walker - Death Star - well aimed bomb.

[TeddyDiver]

Originally Posted by barnakiel

Few inexpensive boat electronics exist in 24V version, in some parts of the world (I think). 24V seems more commercial stuff - for fishers, cargoes, etc.

All the less expensive VHFs, AISs, etc. instruments I have seen were in 12V system. I have also seen fewer 24V LED panels and such likes.

Maybe this is country specific, we are in the EC, mostly.

I would stick with 12V unless heavy gauge equipment (big windlass, big bowthruster) are an issue.

b.

You can allways use one of these 24 volt to 12 volt DC/DC converters (fully regulated) from 100 to 700 Watts both non-isolated and isolated. to use common 12v gadgets in a 24v system..

[longjonsilver]

Originally Posted by a64pilot

You can do it, it will cost a bunch of money and only you can determine if its worth it or not, my vote is no, but I'm cheap.

If you'll remember the opening post in this thread i said that the boat that i'm looking to buy had "old or mostly non-existant electronics." Simrad's new 4G radar with chartplotter and sonor are Voltage: 9V to 31.2V DC (12/24V systems)

Originally Posted by a64pilot

I bet your 12VDC starter will be just fine on 48V also, but your going to need a new alt and regulator and of course chargers. Many, many Ford tractors were converted to 12VDC from 6VDC 40 or 50 years ago and the starters are fine.

i was thinking the same thing about the starter (and assuming that you mean 24v not 48v) because - unless the diesel has compression or fuel issues - the starter will just get a burst of power - not a continuous stream, and won't have a chance to overheat

Originally Posted by TeddyDiver

You can allways use one of these 24 volt to 12 volt DC/DC converters (fully regulated) from 100 to 700 Watts both non-isolated and isolated. to use common 12v gadgets in a 24v system..

Yes, a transformer could be used as well, but transformers have losses of power inherent in them. i'm now finding out that tapping off the center of the battery bank to get 12v will result in "unbalanced" batteries, with one overcharged and one chronically undercharged

[Cadence]

I can't figure out the logic. I'm thinking about buying a boat and want to go from 12V to 24V? I guess you can buy a 24V starter and alternator. It may cost you as much as the boat? If it ain't broke don't fix it. I might see the sense on a larger vessel but not 38' sail boat. Starting a big ass diesel would make sense but not something on a 38' sail boat.
JMHO