48V as main DC voltage on boat - anyone?

[Dsanduril]

Bentley and Audi currently have 48/12 mild-hybrid cars on the road commercially. Delphi is predicting that there will be 14 million units of 48/12 by 2025. Of course it's only a projection and may never come to pass, but 10 years from now we may be here arguing about why you don't have a re-purposed 48/12 car unit with its high power density, lightweight 48V battery.

Just one sample, more and more boats are running air conditioning. At 48V you can run that directly from the DC bus. The concept cars already run AC at 48V, so you'll likely be able to pick up an automotive unit for low $. They're also moving to electrical water pumps at 48V, as RPM dependent water flow is not optimum. This can be especially true in marine diesels operating in cold water, where they may never reach proper operating temperature because of too much water flow. A variable speed 48V electrical water pump can adjust flow to meet cooling requirements. Cars are going this way because all the RPM dependent equipment (pumps, AC compressors) robs them of efficiency numbers. With higher and higher efficiency requirements they think they can get 10-15% gains in fuel economy simply from switching to independent units for each job that can be separately controlled to meet requirements.

It makes all the equipment more complicated, and flies in the face of my own KISS preferences, but I find the topic at least interesting and could see doing some experiments. Are there potential problems and dangers? Sure. Same thing is true of 12V systems.

[ranchero76]

Originally Posted by cyan

Fair enough. In the USA, a BSEE degree means an "Electrical Engineer", and also deals with electronics. Your country might use different terminology, but that's cool.

I honestly like your thinking. 48V is out of the box and this is a great forum for sharing experience.

However, you belittled those who were being helpful by writing that they were "scared". We can all help each other here without such denigration perhaps. No?
48V on a boat has some challenges, and why not explore them here? Some of us have done rocket science.
This isn't that.

I've started this thread not to discuss options. It's simply wrong forum for this, too many sceptics kill any discussion on the spot - been there many times. I have my point of view and arguments, but rather would not discuss them here.
That's why I simply asked for first hand experience, if any.

[smac999]

Originally Posted by ranchero76

3kW 12V to 240V inverter - that's 250A current from battery! It's just insane! 3kW 48V to 240V inverter - 62.5A of current. Huge difference!

250a is not much. 4/0 wire no issue. most 12v bow thrusters are in the 500-600a range.

wether you have a 3000w inverter at 12 or 48v. the same number of batteries will last the same amount of time. it will make no difference. IE 4 batteries at 12v or 4 at 48v either way you need lots of batteries to run inverters. only diff is cable size.

[cyan]

Originally Posted by ranchero76

I've started this thread not to discuss options.

One option is indeed 48V.
I'm glad you started the thread.
Peace.

[ranchero76]

Originally Posted by Dsanduril

Bentley and Audi currently have 48/12 mild-hybrid cars on the road commercially. Delphi is predicting that there will be 14 million units of 48/12 by 2025

Cars are totally different animals, with different needs.
Big boat is much closer to a house. No one in his right mind would consider 12V as main voltage for the middle size house. The only concern is that boat is house on water. So, 240V AC wherever is safe, 48V for most power hungry appliances in "not so safe" locations and for "always on" appliances (having 48V battery bank means no inverter needed for them, simplicity and no power loss) , and 12V for these "hard to convert" devices (if any).

[ranchero76]

Originally Posted by smac999

250a is not much. 4/0 wire no issue. most 12v bow thrusters are in the 500-600a range.

And most bow thrusters have dedicated battery sitting nearby, not needed in case of 48V system.

Originally Posted by smac999

wether you have a 3000w inverter at 12 or 48v. the same number of batteries will last the same amount of time. it will make no difference. IE 4 batteries at 12v or 4 at 48v either way you need lots of batteries to run inverters. only diff is cable size.

Do you realize how much power will be lost in these 4/0 wires? Do you realize that reliability heavily depends on current? Chance of burning 3kW 12V/240V inverter much higher than 3kW 48V/240V inverter, just because there are no insane currents in DC circuit of 48V inverter. Even if system has proper breakers and protection.

Now imagine that you have huge battery bank (say 60kWh) and few inverters, so you can run few power hungry devices at the same time. Like dive compressor and water maker (or AC and water maker, or whatever). Let's imagine that you have two inverters, each will have 4kW load. At 95% efficiency together they will draw 700A CONTINIOUSLY from battery. Even though lithium batteries might handle this OK, I wouldn't count on reliability of such system.
Same 2x4kW load in 48V system with 95% efficiency will draw 175A from batteries. While not particularly small number, it's definitely not as scary as in 12V system.

1kW 12V starter motor will be overheated in just few minutes under full load. 1kW 240V motor will run continuously without overheating at all. It's just an example.

[Dsanduril]

Originally Posted by ranchero76

Cars are totally different animals, with different needs....

Don't disagree with you on that. But, in the grand scheme of things boats are a pretty small niche market. So if a much larger market (cars) develops the technology and pays for the development costs....

Here they are, developing exactly what you're discussing/looking for - seems like a great place to begin stealing and adapting.

You asked for practical experience, the only case I have is the Duffy boats, they've been running 48V lead-acid systems for 20+ years. I've worked on masses of those, some of it translates to a liveaboard, some of it doesn't. Same with automotive gear.

[ranchero76]

Originally Posted by Dsanduril

Don't disagree with you on that. But, in the grand scheme of things boats are a pretty small niche market. So if a much larger market (cars) develops the technology and pays for the development costs....

Here they are, developing exactly what you're discussing/looking for - seems like a great place to begin stealing and adapting.

You asked for practical experience, the only case I have is the Duffy boats, they've been running 48V lead-acid systems for 20+ years. I've worked on masses of those, some of it translates to a liveaboard, some of it doesn't. Same with automotive gear.

Not much of automotive technology translates to boats. On other hand, all the technology already exists. Solar panels and wind generators easily arranged in 48V manner. 48V DC motors are plenty, even though not as many as 12V and 24V. Arranging battery bank for 48V - simple. Programmable charge controllers can be easily set to handle 48V. LED lights - no problem. Even dealing with 12V devices can be easy - there are smart battery managing systems controlling voltage of each cell. So 12V can be taken from few cells of 48V bank, these cells later will be recharged to match exactly voltage of other cells.

[Dsanduril]

Originally Posted by ranchero76

Not much of automotive technology translates to boats....

I guess we'll have to agree to disagree. Pretty much every (small) marine diesel engine is a re-badged, barely modified industrial engine with an ECU and common-rail, both of which came out of the automotive industry. Both developed in search of better fuel economy and emissions limits imposed on the auto industry.

They come with alternators straight out of the automotive industry. One of my biggest beefs with the marine industry is that the "marinization" of these auto industry items is terrible.

Many boats have been fitted with CV joints straight out of cars to help with alignment and thrust issues. Not because they're particularly suited to service in the bilge, but because they are readily available and adaptable.

The forced air diesel heaters found on boats that operate in colder climates come straight out of the truck/bus/RV market segment without any modification.

There are several threads around here about adapting EV batteries to boating use.

He||, the crappy but ubiquitous cigarette lighter 12V connection comes out of the automotive market and is found all over boats (another terrible adaptation).

I could go on, but why?

[valhalla360]

If you have the equipment, knowledge and enjoy rewinding electric motors...have at it. It can certainly be done.

As someone else mentioned, for most 12v/24v circuits, the minimum wire size for physical strength controls not the ability to handle the amps, so don't count on a lot of reduction in wire size.

If you are going to go for propulsion, 48v can make sense because now you are talking amperage way beyond what normal DC circuits see (outside of starters).

Another issue (which you may not care about but it's real)...what happens to resale on a boat with a goofy electrical system. If I see some goofy system, I'm either not going to put a bid in or I'm going to adjust my bid based on the assumption that at some point I will have to rip it all out and put in a normal system.

[ranchero76]

Originally Posted by Dsanduril

I guess we'll have to agree to disagree. Pretty much every (small) marine diesel engine is a re-badged, barely modified industrial engine with an ECU and common-rail, both of which came out of the automotive industry. Both developed in search of better fuel economy and emissions limits imposed on the auto industry.

They come with alternators straight out of the automotive industry. One of my biggest beefs with the marine industry is that the "marinization" of these auto industry items is terrible.

Many boats have been fitted with CV joints straight out of cars to help with alignment and thrust issues. Not because they're particularly suited to service in the bilge, but because they are readily available and adaptable.

The forced air diesel heaters found on boats that operate in colder climates come straight out of the truck/bus/RV market segment without any modification.

There are several threads around here about adapting EV batteries to boating use.

He||, the crappy but ubiquitous cigarette lighter 12V connection comes out of the automotive market and is found all over boats (another terrible adaptation).

I could go on, but why?

Ok, maybe I'm a little incorrect
I had in mind electrical and electronic systems (not related to engines). They're very different. EV batteries not something unique, they're using universal cells. AC/heat systems are closer to ones in the houses.
And that lighter socket is terrible example Hopefully it will be replaced with something more reliable!

One thing is certain - cars manufactured in huge quantities, and any related technology evolved much faster.

[ranger58sb]

Originally Posted by ranchero76

I've got couple replies with useful information, the rest are just opinions of people who scared of anything non-standard.

Opinions? Sure. Scared? No, probably not.

At least in my case, I just don't see any benefit ("4 times less current in all wires" matters not to me)... and it would also create problems.

I don't mind non-standard... until it causes me more work than necessary.

-Chris

[Jammer]

Originally Posted by Zven

Here is one aspect that would probably not be an issue: Lights.
24V light bulbs are easy enough to find, LED or otherwise...
So just connect two in series, everywhere some light is required.
Red and green lantern goes in series, for example.
Viola, all lighting is 48V :-)
The same trick might even work for some other equipment .. E.g two bilge pumps. Could get complicated though :-)

The problem with this line of reasoning is that the impedance has to be balanced.

It was easier of olden time with incandescent lamps, but, the problem then was that over time the filaments would deteriorate at uneven rates, and there was a runaway effect where the one that first developed a slightly higher resistance would be subject to a higher voltage, which would cause it to deteriorate all the more quickly. So two lamps in series would have about half the median life of a single lamp. Some bulbs were available in matched pairs for series use that were supposed to improve your chances.

Now, red and green LEDs, most of these things have some sort of switching power supply internally to drop the voltage to whatever the LEDs themselves actually need. So the current draw isn't constant. Connect them in series, might work, might not, might last a long time, or not, who knows. And there's no guarantee that the red and green will draw the same current, because LEDs of various colors have varying efficiencies.

With pumps it's worse. Put two pumps in series, if either one fails neither one works. The current drawn by pumps is variable depending mainly on flow rate, result is that if one pump is sucking air or clogged it will get too much voltage and the other too little.

Electricity is more complicated than most people realize.

[GordMay]

Originally Posted by ranchero76

... That's why I simply asked for first hand experience, if any.

The automotive industry has considerable experience with higher (42V & 48V) voltage DC systems.

In 1995, the (Auto) industry agreed-with help from MIT’s Laboratory for Electromagnetic and Electronic Systems-on a new standard of 42 volts. Industry leaders also realized it made sense to create a formal consortium, headquartered at MIT, to help implement the standard. Today (2002) some 52 companies-automakers and major suppliers-each contribute $50,000 annually to the lab in support of the MIT/Industry Consortium on Advanced Automotive Electrical/Electronic Components and Systems, based in the electromagnetic and electronic systems lab.
See ➥ https://www.technologyreview.com/s/4...volt-standard/

This program failed. Some of the reasons* are examined here (previously linked):
➥ https://www.popularmechanics.com/cars/a2198/4226979/

* One reason was/is the difficulty of arc-quenching 42/48V DC (vs lower V) switching applications.

About the CURRENT 48V System proposals (also, previously linked):
➥ http://www.aboutpublishinggroup.com/...48V_sample.pdf

[TheThunderbird]

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