System change 12v to 24 or 48v

[freshalaska]

What would be the advantages disadvantages of converting my boats 12 volt system to 24v or 48v ? I’d be using lithium ion batteries. Not sure if the conversion would be worth it as most wiring and fusing is already in place for 12v. Just a thought at this point. What do you think.

[s/v Jedi]

Originally Posted by freshalaska

What would be the advantages disadvantages of converting my boats 12 volt system to 24v or 48v ? I’d be using lithium ion batteries. Not sure if the conversion would be worth it as most wiring and fusing is already in place for 12v. Just a thought at this point. What do you think.

We need more information. What do you power with it? Do you plan to convert the galley from propane gas to electric? Do you run other high power appliances like water maker, A/C ?

How many kWh (or Ah at 12V) batteries do you have and is that enough? What kind of batteries do you have now?

[Networker]

Originally Posted by freshalaska

What would be the advantages disadvantages of converting my boats 12 volt system to 24v or 48v ? I’d be using lithium ion batteries. Not sure if the conversion would be worth it as most wiring and fusing is already in place for 12v. Just a thought at this point. What do you think.

From my research, unless you have long cable runs on larger boats, there's no benefit. I wanted to go 24v on my boat outfit 3 years ago as I thought it sounded cooler, but couldn't find one advantage other than the wiring runs. In fact, it seemed like a pain to search and replace all 12v items with 24v for no benefit.

In some niche use cases, 24v or 48v banks of batteries to power crazy large alternators or oceanvolt electric engines are necessary, but even then, you'd probably still want 12v in the cabin.

[SailingHarmonie]

Originally Posted by freshalaska

What would be the advantages disadvantages of converting my boats 12 volt system to 24v or 48v ? I’d be using lithium ion batteries. Not sure if the conversion would be worth it as most wiring and fusing is already in place for 12v. Just a thought at this point. What do you think.

You do need to articulate WHY you think this is a good idea.

There is no reason I can think of to change an existing 12V system that works to anything else for no reason other than it's what all the cool boats have.

If you are making major electrical modifications to the boat, it MIGHT be a good idea to go to 24V. I can not see a good reason for most boats to move to 48V absent VERY large power needs.

[Fintry]

First, very few boats that have 24VDC get away from 12VDC completely.

NMEA 2000 requires 12 volts, which could be done with a small DC-DC converter, but radios also require it, although there are expensive SOLAS radios that will run on 24VDC. Now that masthead lights draw only milliamps, saving wire size and weight will not justify it. The one thing that might justify it is that largest inverter you can run on 12V is 3kW. If you want to run several air conditioners, you will probably need more. But even there, you could simply run two 12V 3kW inverters and cool most boats in the sizes we have here.

As for 48VDC, several manufacturers offer 48V windlasses and thrusters, so if I were going up voltage, I would skip 24V and go all the way to 48V, using it for the windlass, thruster, and inverter, keeping 12V for everything else.



Jim

[s/v Jedi]

Originally Posted by Fintry

First, very few boats that have 24VDC get away from 12VDC completely.

NMEA 2000 requires 12 volts, which could be done with a small DC-DC converter, but radios also require it, although there are expensive SOLAS radios that will run on 24VDC. Now that masthead lights draw only milliamps, saving wire size and weight will not justify it. The one thing that might justify it is that largest inverter you can run on 12V is 3kW. If you want to run several air conditioners, you will probably need more. But even there, you could simply run two 12V 3kW inverters and cool most boats in the sizes we have here.

As for 48VDC, several manufacturers offer 48V windlasses and thrusters, so if I were going up voltage, I would skip 24V and go all the way to 48V, using it for the windlass, thruster, and inverter, keeping 12V for everything else.

Jim

You would do that just because it exists? This decision must be based on technical values, not marketing.

[Mal Reynolds]

The reason to move to 48v for storage and charging is to reduce engine run time and/or replace a generator. 48v alternators charge at astonishingly high rates, and lithium can absorb it.

Loads can stay at 12 or 24v via DC-DC step down converters at 95%+ efficiency. Use a service battery to absorb motor startup load spikes that just stays in float.

[s/v Jedi]

Originally Posted by Mal Reynolds

The reason to move to 48v for storage and charging is to reduce engine run time and/or replace a generator. 48v alternators charge at astonishingly high rates, and lithium can absorb it.

Loads can stay at 12 or 24v via DC-DC step down converters at 95%+ efficiency. Use a service battery to absorb motor startup load spikes that just stays in float.

Nope. A 12V boat that uses DC power for a fridge, navlights and some electronics doesn’t need 48V even when they want to minimize engine run time etc.

We simply need to know from the OP what plans he has as I asked earlier.

[Emoyeni]

A cheaper solution would be to just have two separate systems, and a DC to DC converter in between.

[Fintry]

Originally Posted by s/v Jedi

You would do that just because it exists? This decision must be based on technical values, not marketing.

Except for human safety issues, higher voltage is almost always better. If the DC motors have brushes, 48V has half the current through the brushes vs 24V. Even if you keep the runs short, 48V will require smaller wire or have lower voltage drop or both. Switching DC is hard -- the contacts arc as they open -- and 48V relays and switches will last longer. To be sure, the design life is many thousands of operations, but how many of us have had a switch or relay fail?


Although the difference is not large, 48V inverters are a little more efficient than 24V models and the zero load power draw is less (see the data sheet on Victron Multiplus-II 3kVA). That's as I would expect, as solid state devices have a constant voltage drop, so on a percentage basis are twice as effective.



Once you decide to spend the time and money to use a higher voltage on board, I see no reason to stop at 24V now that heavy load equipment is available for 48 volts.



Jim

[Jammer]

Originally Posted by freshalaska

What would be the advantages disadvantages of converting my boats 12 volt system to 24v or 48v ? I’d be using lithium ion batteries. Not sure if the conversion would be worth it as most wiring and fusing is already in place for 12v. Just a thought at this point. What do you think.

24v or 48v will provide better support for high-power charging sources and loads and might be worth looking at if you are planning an electric galley conversion, electric propulsion, or running electric heat or A/C at anchor.


The drawback is that you have to replace a lot of expensive stuff unless you're going to leave a substantial 12v system in place. Alternator, inverter/charger, pumps, windlass and winch motors. Starter motor can be problematic. As noted upthread, navigation and communications electronics are a problem area.


48v is worse than 24v conversion wise because most leisure marine products are not available in 48v (LEDs etc).

[freshalaska]

If I had a 24 or 48 volt lithium battery it would charge much faster with an approbate alternator. Then I could step it down to 12v to run all the electronics and appliances on board. I think 24 and 48 volt lithium batteries are cheaper per watt hour than 12 volt. Correct me if I’m wrong.

[RaymondR]

The two major benefits to be realised from higher voltages are reduction of conductor size and reduced heat buildup.

[Bowdrie]

Yep, multiple voltages, what was old becomes new again.
Just like the '61 Chris-Craft I spent an uncountable amount of time on.
She had 12, 24, and 32V systems.
The starters for the Jimmys, the inverter, windlass, searchlight, and all of the original lighting was 32V.
Electric toilets. water pressure, and davit winch at 24V.
Various gizmos/electronics/pumps at 12V.
The DVM became your friend.

[s/v Jedi]

Originally Posted by freshalaska

If I had a 24 or 48 volt lithium battery it would charge much faster with an approbate alternator. Then I could step it down to 12v to run all the electronics and appliances on board. I think 24 and 48 volt lithium batteries are cheaper per watt hour than 12 volt. Correct me if I’m wrong.

You can buy a powerful 12V alternator too so no, I think you should stay at 12V unless you answer the questions asked which may change the recommendation.