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Old 14-04-2018, 16:15   #1
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48V as main DC voltage on boat - anyone?

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.
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Old 14-04-2018, 17:41   #2
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Re: 48V as main DC voltage on boat - anyone?

You are right the current would be substantially lower. However you would still have to convert it to 12 or 24 volt to power most electrical or electronic equipment. That would mean additional hardware & cost. Instead of one failure point you now have two.

A lot of big boats with large 120vac loads use 48Vdc or 72Vdc or even 120vdc battery banks to power their inverters.
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Old 14-04-2018, 19:56   #3
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Re: 48V as main DC voltage on boat - anyone?

All electric motors can be replaced or rewinded for 48V. Once done, it's easy to do repairs and keep spares as needed.
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Old 14-04-2018, 20:19   #4
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Re: 48V as main DC voltage on boat - anyone?

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Originally Posted by ranchero76 View Post
All electric motors can be replaced or rewinded for 48V. Once done, it's easy to do repairs and keep spares as needed.


It's not the motors that are the issue. Every instrument and light is either 12 or some at 24v. Every time you change voltage you have another point of potential failure. The saving is a bit of heavier duty wiring.
Starting batteries at 24 volts make sense to me. Perhaps the anchor windlass. If you have lots of sail handling winches then they may also be advantaged.
But where do you get someone to help you with rewinding in the many remote locations we go to. In the main rewinding will be the only solution as it will be difficult to buy spares even from the manufacturers. Salt water and salt air are the biggest killers of power supply. Not wire gauge.
Incidentally I always convert my starter to 24v but 24 v starters are common to most larger trucks so easier to find spares.
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Old 14-04-2018, 21:03   #5
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Re: 48V as main DC voltage on boat - anyone?

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It's not the motors that are the issue. Every instrument and light is either 12 or some at 24v. Every time you change voltage you have another point of potential failure. The saving is a bit of heavier duty wiring.
Starting batteries at 24 volts make sense to me. Perhaps the anchor windlass. If you have lots of sail handling winches then they may also be advantaged.
But where do you get someone to help you with rewinding in the many remote locations we go to. In the main rewinding will be the only solution as it will be difficult to buy spares even from the manufacturers. Salt water and salt air are the biggest killers of power supply. Not wire gauge.
Incidentally I always convert my starter to 24v but 24 v starters are common to most larger trucks so easier to find spares.
Of course there will be 12V, for instruments, for example. I don't see problems with that.
Lightning - LED and only LED, so there's no problems to adapt it to 48V.
Regarding the motors - spares can be made at the time building/refit for pennies comparing to manufacturers prices.
48V makes sense on a big boat with lots of solar, lots of battery power, lots of equipment. 12V in powerful equipment not only hard on wiring, it's hard on equipment itself.
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!
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Old 14-04-2018, 21:43   #6
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Re: 48V as main DC voltage on boat - anyone?

Not the kind of boats most of the people here run, but Duffy Electric Boats are a fixture in southern California harbors. They are all 48V traction systems and use converters for 12V house loads.

Many telecom UPS systems are 48VDC so there are a fair number of lights (including LED) and some other appliances that can be run directly and are marine friendly.

Lots of 48VDC input inverters available for running the modern high-power conveniences (and much easier to wire with 4x reduction in input current).

For the rest, there are any number of 97+% efficient 48-12 DC-DC buck voltage converters that can provide 12V where required. These can also provide the advantage of giving stable output voltage while going through the charge/discharge cycles on the battery.
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Old 15-04-2018, 01:30   #7
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Re: 48V as main DC voltage on boat - anyone?

It seems to me that 48v makes sense for bulk storage of power for an inverter on a really big boat.

24v is practical for quite a lot of electrical gear, and the halving of current really helps with cabling for big consumers like bow thruster, windlass, electric furlers & winches, etc. Dropping 24v to 12v for a few small consumers is cheap and reliable -- no big deal. You can get all possible lighting and a lot of electronics in 24v, and not just the big consumers.

No need to rewind any motors. Imagine for a moment that you are out cruising and your windlass motor burns out. What are you going to do? First of all, you have to get the motor. THEN, you have to get it rewound. How long will you be down waiting for all that to happen, versus just getting and putting in a standard part?

So just doing 24v will be much simpler, cheaper, more elegant.
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Old 15-04-2018, 02:03   #8
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Re: 48V as main DC voltage on boat - anyone?

Rewinding - that's just one of the options, may be, not most "elegant".
Another - finding similar 48V motor, direct fit or with adapter. Just checked eBay - there are literally thousands of them, with any parameters.
That's actually was my question - if anyone was brave enough to do this.
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Old 15-04-2018, 03:15   #9
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Re: 48V as main DC voltage on boat - anyone?

Back in the late 90's, the automotive industry was expected to make a transition in design from 14-volt (12V nominal) to 42-volt (36V nom) electrification systems. It never happened.

Whatever Happened to the 42-Volt Car? ➥ https://www.popularmechanics.com/cars/a2198/4226979/

48V ➥ http://www.aboutpublishinggroup.com/...48V_sample.pdf
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Old 15-04-2018, 03:57   #10
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Re: 48V as main DC voltage on boat - anyone?

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Imagine for a moment that you are out cruising and your windlass motor burns out. What are you going to do? First of all, you have to get the motor. THEN, you have to get it rewound. How long will you be down waiting for all that to happen, versus just getting and putting in a standard part?

So just doing 24v will be much simpler, cheaper, more elegant.
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Originally Posted by ranchero76 View Post
Rewinding - that's just one of the options, may be, not most "elegant".
Another - finding similar 48V motor, direct fit or with adapter. Just checked eBay - there are literally thousands of them, with any parameters.
That's actually was my question - if anyone was brave enough to do this.

Mostly when you need a replacement windlass while cruising you need it RIGHT NOW. Ditto freshwater pumps, autopilot stuff, etc... I think the point is that you can get 24V (or 12V) stuff RIGHT NOW without having to leap through too many hoops, so installation can happen RIGHT NOW and you can get on with whatever cruise you're in the middle of...

"RIGHT NOW" being a relative concept, given sometimes need for shipping, etc... but still, likely faster than custom or at least not-off-the-shelf work.

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Old 15-04-2018, 04:03   #11
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Re: 48V as main DC voltage on boat - anyone?

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so installation can happen RIGHT NOW and you can get on with whatever cruise you're in the middle of...
I understand this, but I think one would need to have spares for that. I suspect that in the middle of something neither 12V, 24V or 48V exact match motors (or whatever) will be available. And temporary solution for any motor can be made (skills and tools dependent).
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Old 15-04-2018, 05:06   #12
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Re: 48V as main DC voltage on boat - anyone?

Quote:
Originally Posted by ranchero76 View Post
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.
I've worked with some large 48 vdc power systems. It is the standard voltage for central-office telephone equipment, and has been for 100 years. When cellular telephone became a thing, 24 vdc was chosen for the power systems for cell sites, and all major equipment manufacturers have stayed with it.

Leaving aside compatibility questions, the problem with 48 vdc is that it is significantly more hazardous to work on than 24 vdc. 48 volts is enough to pose a hazard of injury from electric shock. There is also a much more serious burn risk from inadvertent short circuits as can happen if a tool is dropped across terminals.

For large loads on a boat (windlass, bow thruster, and power winches), the usual progression as the boat gets larger is 12v -> 24v -> hydraulic -> 3 phase AC. 48 volts isn't a standard voltage for marine uses, and so any savings in cable cost is going to be overcome by the cost of custom-wound motors.

If you're going to go to the trouble and expense to insulate everything well enough to be safe for 48v, you might as well go to 208 volt three phase AC.

I guess the question I would ask back to you is: What large loads do you have that are driving you to explore a 48 volt system?
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Old 15-04-2018, 05:53   #13
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Re: 48V as main DC voltage on boat - anyone?

you also have to factor in that to get any sort of storage capacity,you will need at least 4 batteries per bank,or if using 6v trojans ,8 batteries.

which depending on the size of boat,has weight and space implications,as all the batteries in a bank need to be close together for charging as a balanced bank

ie 4x 100AH AGM =100 AH@48v
or
8x T105 225AH lead acid=225AH@48v

using a 3kw inverter at full power would pull down the 100AH AGM bank to 50% soc in about 40 minutes,which would greatly reduce battery life if done on a regular basis,so probably you would want at least twice that capacity,meaning that you would need either larger AH batteries or 8-12 batteries per bank to increase capacity.

using lithium batteries would reduce the weight,and provide more usable AH,but increase the cost substantiially
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Old 15-04-2018, 07:04   #14
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Re: 48V as main DC voltage on boat - anyone?

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I understand this, but I think one would need to have spares for that. I suspect that in the middle of something neither 12V, 24V or 48V exact match motors (or whatever) will be available. And temporary solution for any motor can be made (skills and tools dependent).
Yeah, but some common systems don't often warrant spares unless one is expecting crap out soon (windlass, for example), and then sometimes the fastest/easiest replacement is the whole system (windlass, for example), not just the motor.

I think.

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Old 15-04-2018, 08:20   #15
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Re: 48V as main DC voltage on boat - anyone?

48v has 4 times less current "In the wires" compared to 24v, not 12v.

There is some momentum in the automotive, RV and trucking industries to move to 48v systems. I was in a meeting this week with a major maker of batteries here in the us, and they confirmed that their customers are looking to go this route. It seems that it takes about 10 years for technology from the automotive world to reach the marine one. I know of some efforts to make this a shorter timeframe. Most likely you would see 48v at the generation and storage, and 12 or 24v for the consumers.

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Originally Posted by ranchero76 View Post
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.
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