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Old 16-04-2018, 07:06   #61
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Re: 48V as main DC voltage on boat - anyone?

Even going to 24v is a stretch as there is so little marine equipment designed for it in the consumer market. Go into a WestMarine or local chandlers and ask for a 24v VHF or chartplotter and wait for the strange looks. Maybe in a few years marine electronics makers will start making dual-voltage equipment that can adjust to anything like solar power controllers do these days.

If you wanted a 48v bank for your inverter plus maybe bow thruster and windlass but then split off everything else onto a 12v system that is somewhat doable. But 95% + of the boat would still be on the old standard 12v anyhow. Or have 3 systems, 48/24/12 which is just needless complication and more things to go wrong.

I see a lot more LED light manufacturers offering 24v wiring options which amounts to basically a matching resistor you put inline to drop the voltage back down to 12v. Cha, right...all that is doing is wasting half of the power in heat so anything you might save in wiring would be wasted with use. LEDs draw almost nothing anyhow so modern lighting circuits could theoretically be downsized but I personally think that is stupid. I don't have a single main wiring run smaller than 12AWG on my boat with a few 14AWG short "whips" of 2-3 feet from the main run to the device since all the #12 wire is run in conduit to junction boxes. The longest of these whips run up through the bow pulpit and stern rail to LED nav lights that draw a fraction of an amp even at 12v and those only run about 6 feet before they tap onto #12 wire for the run back to the DC panel. I'd have pulled #12 but Ancor marine boat romex gets really big by #12 and #14 duplex boat cable was all that I could fish inside them. The DC voltage drop on my AquaSignal series 34 LED nav lights is calculated at less than 1%. Voltage drop is everything and the whole reason you would want to run a higher voltage system in the first place. Where is the problem here?

12v DC is a standard that will be around for a long time. 24v is starting to make some traction but I don't see many people having a full 24v DC boat these days because it is just not supported by the industry. 48v is a boutique DC voltage in consumer marine use maybe for really big inverters and specialty high-current loads. Big copper isn't all that expensive compared to weird systems. Run some 4/0 wire and keep the runs really short. Put a dedicated battery near the bow thrusters and/or windlass if it is an issue. $1000 will buy you a LOT of heavy duty cable and even batteries -but is chicken-feed when you get into fancy inverters. and high-voltage DC equipment. Big copper will get you more results than trying to reinvent the wheel and changing standards that have been around for nearly 100 years.
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Old 16-04-2018, 07:35   #62
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Re: 48V as main DC voltage on boat - anyone?

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Originally Posted by TheThunderbird View Post
1) anyone can post here. The thread may develop along individual posts, not necessarily addressing the OP
2) considering current trends, number of accessories... It'd be great if the leisure nautical sector could agree on A move towards a 24 or 36V world. It it can be induced only by the automotive sector.

Sure, l find the 12V standard a gross stupidity, as boats are not like cars with a lighter.

Tomyknowledge, MY usually run 24V. 48V or more make sense for traction only.

I personally feel ok starting Genny for 220V when needed
The leisure boating industry made a half assed stab at a 32VDC system in the 50s.
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Old 16-04-2018, 08:32   #63
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Re: 48V as main DC voltage on boat - anyone?

MOST of the larger yacht systems we do are now 24V, not 12V Sometimes there is a small backup 12V battery to keep the 12V nav or lighting running in the case of a main bank LVC.

You will soon see more high-performance yachts going 48V (actual nominal for Li systems will be 51V) for the charging & batteries, as it is considerably more efficient and less weight. One example of the charging efficiency: A 28V x 185A American Power HPI alternator is cold-rated at 185A, and the same size unit in 56V is cold-rated at 150A. If hot outputs are 80% (usually are more, however for calculation purposes) that's 4.1kW for the 28V and 6.7kW for the 56V. Note that I'm using actual charging voltages vs. nominal.

Anyhow, that's at least 50% more output in kW, from the same size alternator, through cables that are 1/2 the weight. The inverter conversion efficiency to the AC loads is also more efficient at the higher DC voltage.

Note that residential energy storage is already going to much higher DC voltages (288V to 360V), for the same gains in efficiency. However that level would not be very safe on a boat...
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Old 16-04-2018, 09:09   #64
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Re: 48V as main DC voltage on boat - anyone?

Yep, thanks for the correction. I should know better than to try and post here while doing our taxes.

So to summarize, moving from 24v to 48v would reduce the cross-section of a wire to 1/4 of the size, with a given load. the cross-section of a wire in a 48v system would be 1/16th of what would be needed on a 12v system.

Chris

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Slight miscalculation there
You are leaving it at 20A when doubling the voltage, so you are changing the power requirement from 480W to 960W

Keeping it at 480W (20A @ 24V, 10A @ 48V) gives you 16mm˛ and 4mm˛.

Of course, a lot depends on what you mean by "size".
A 16mm˛ wire is only twice as "thicK" as a 4mm˛ wire (2.26mm diameter v 4.52mm diameter)

And if you have unidentified wire, it's a lot easier to measure its diameter than its cross-sectional area.
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Old 16-04-2018, 10:03   #65
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Re: 48V as main DC voltage on boat - anyone?

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Originally Posted by witzgall View Post
Yep, thanks for the correction. I should know better than to try and post here while doing our taxes.

So to summarize, moving from 24v to 48v would reduce the cross-section of a wire to 1/4 of the size, with a given load. the cross-section of a wire in a 48v system would be 1/16th of what would be needed on a 12v system.

Chris

Cutting it a bit thin on taxes?
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Old 16-04-2018, 10:57   #66
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Re: 48V as main DC voltage on boat - anyone?

Naw, Doing them tonight would be cutting it thin.

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Cutting it a bit thin on taxes?
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Old 16-04-2018, 11:21   #67
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Re: 48V as main DC voltage on boat - anyone?

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Naw, Doing them tonight would be cutting it thin.
Mailed in what we owed over the quarterlies Sat..
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Old 16-04-2018, 11:28   #68
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Re: 48V as main DC voltage on boat - anyone?

Yes 48v is a standard ship system, is it appropriate for boats under 50ft? If you are a very high power user, particularly mains power I can see the point of a 48v house bank and inverter to power that system. You would almost certainly also be in the range where you wanted to run a genset (for washing machine, dryer and maybe stove). I would suggest looking at making this a separate system but including a mains 12 or 24v charger. Then look at running ships systems and lighting from a second 12/24v bank and hook this one up to the engine alternator.
Reason - while higher voltage reduces current which allows you to cut down on wiring size this only applies to high power circuits. Min size is generally 14g, maybe 16 for interior lighting. Any less is physically to fragile, particularly at connectors, to be reliable. so for less than about 15a there is no benefit
Second point - As voltage increases current decreases but LEAKAGE increase. If you run 48v in a damp salty atmosphere you may get far more problems with corrosion and possibly electrolysis. Big steel ships cope with this by being generally drier (due to freeboards measured in meters not feet) and by using solid conduits and sealed wiring systems with big sealed switch gear. On a smaller boat this may be excessively expensive and impractical for most systems.
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Old 16-04-2018, 11:37   #69
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Re: 48V as main DC voltage on boat - anyone?

Quote:
Originally Posted by OceanPlanet View Post
MOST of the larger yacht systems we do are now 24V, not 12V Sometimes there is a small backup 12V battery to keep the 12V nav or lighting running in the case of a main bank LVC.

You will soon see more high-performance yachts going 48V (actual nominal for Li systems will be 51V) for the charging & batteries, as it is considerably more efficient and less weight. One example of the charging efficiency: A 28V x 185A American Power HPI alternator is cold-rated at 185A, and the same size unit in 56V is cold-rated at 150A. If hot outputs are 80% (usually are more, however for calculation purposes) that's 4.1kW for the 28V and 6.7kW for the 56V. Note that I'm using actual charging voltages vs. nominal.

Anyhow, that's at least 50% more output in kW, from the same size alternator, through cables that are 1/2 the weight. The inverter conversion efficiency to the AC loads is also more efficient at the higher DC voltage.

Note that residential energy storage is already going to much higher DC voltages (288V to 360V), for the same gains in efficiency. However that level would not be very safe on a boat...
Have to agree most of the boats over 40' I deal with are now 24VDC. 48VDC is talked about a lot and I think we will start to see more of it. I have only been on two boats with it thou. One had electric propulsion the other used it for a large inverter bank only. Both also had 12V systems for typical loads.
I was drawing up a diagram for a racer cruiser with multiple electric winches, bow thruster and windlass. On that boat a 48VDC system would reduce wire size issues quite a bit.
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Old 16-04-2018, 13:01   #70
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Re: 48V as main DC voltage on boat - anyone?

Being electronics engineer, it's very painful to read some replies... Like "using LED lights on 48V circuit will generate more heat" or "connecting them in series might work, might not"... Won't even comment, I'm speechless.
But anyway, I want to summarize few thoughts from replies above.

"Note that residential energy storage is already going to much higher DC voltages (288V to 360V), for the same gains in efficiency. However that level would not be very safe on a boat..."

- That's why I have 48 number in mind - anything above is less safe. Still, for all dry locations 220V-240V is way to go.

"Yes 48v is a standard ship system, is it appropriate for boats under 50ft? If you are a very high power user, particularly mains power I can see the point of a 48v house bank and inverter to power that system. "

"You will soon see more high-performance yachts going 48V (actual nominal for Li systems will be 51V) for the charging & batteries, as it is considerably more efficient and less weight. "

- That's exactly what I had in mind - somewhat "luxury" catamaran over 50ft, with lots of power-hungry devices, with hundreds and hundreds kilograms of wiring.
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Old 16-04-2018, 13:09   #71
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Re: 48V as main DC voltage on boat - anyone?

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Originally Posted by ranchero76 View Post
Being electronics engineer, it's very painful to read some replies... Like "using LED lights on 48V circuit will generate more heat" or "connecting them in series might work, might not"... Won't even comment, I'm speechless.
But anyway, I want to summarize few thoughts from replies above.

- That's exactly what I had in mind - somewhat "luxury" catamaran over 50ft, with lots of power-hungry devices, with hundreds and hundreds kilograms of wiring..
I think you meant, "without" hundreds & hundreds of kg of wiring...;-)
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Old 16-04-2018, 13:16   #72
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Re: 48V as main DC voltage on boat - anyone?

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Originally Posted by Cadence View Post
The leisure boating industry made a half assed stab at a 32VDC system in the 50s.
32v was the standard for railroad lighting systems at that point. There were some similarly half assed efforts to use 32v in the wind power industry in the 1980s.
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Old 16-04-2018, 13:22   #73
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Re: 48V as main DC voltage on boat - anyone?

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If I would be building (or rebuilding) boat, there's no doubt that 48V would be main DC voltage. There's at least one major reason for that - 4 times less current in all wires.

My question - is there someone on the forum who already done this and willing to share experience of converting to 48V? What were major difficulties of doing that? There are boats which came from factory with 24V system, but I never heard about factory installed 48V systems.


A 12V bilge pump is a lot cheaper than a 24V pump which would be cheaper than 32V pump.
A lot of kit is made for 12V. It may come down to availability of stuff in the higher voltages. Use of a transformer increases costs and heat losses in the voltage conversions.

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Old 16-04-2018, 13:30   #74
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Re: 48V as main DC voltage on boat - anyone?

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A 12V bilge pump is a lot cheaper than a 24V pump which would be cheaper than 32V pump.
A lot of kit is made for 12V. It may come down to availability of stuff in the higher voltages. Use of a transformer increases costs and heat losses in the voltage conversions.

Happy Days Sailing
My water ballast pump on OceanPlanet for the AA & Vendee was a 24V 100pgm centrifugal pump. I'm not sure we could even source the same in 12V at the time. Very handy for filling the 700gal ballast tanks. After that, before tacking simply opened a monster gate valve and let gravity do the work...;-)

That's just an example. The little stuff can stay 12V, big loads better at higher voltage. Just as how AC-powered watermakers are needed to make a lot of water, fast.
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Old 16-04-2018, 13:33   #75
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Re: 48V as main DC voltage on boat - anyone?

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Originally Posted by OceanPlanet View Post
I think you meant, "without" hundreds & hundreds of kg of wiring...;-)
Well, there will be many hundreds kg of wiring in any case Just in case of 48V system - not as many hundreds of kilograms
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