48V as main DC voltage on boat - anyone?

[noelex 77]

I am not a fan of the 48v option. It is going to be difficult to find equipment to run on this voltage, and even small components such as many marine fuse holders are not suitable (often the limit is 32v).

This voltage also starts to present a shock hazzard. Over 50v can be fatal in the wrong circumstances. A tired salt water wet owner who has just come off watch to find the electrical fault in a bouncing healing yacht is the wrong circumstance . A nasty shock is more likely than a fatal result, but both of these possibilities mean the electrical ststem needs to more complex with shrouds, covers etc. A 48v battery system will be over 50v when charging. I am sure it could be made to work, and be safe, but not without significant effort. I think there would have to be a compelling reason, such as the installation of 48v electric main engine, to justify this.

However, I think the suggestion that all higher voltages are inherently dangerous and increase the fire risk is also incorrect. A 24v house system does not decrease safety. I would argue that it is safer than a 12v system.

Let’s take a practical example recently reported on Cruisers Forum:

http://www.cruisersforum.com/forums/...ot-212632.html

This involved an ANL fuse holder overheating.

At 12v the fuse holder was carrying around 400A. If the boat had a 24V house bank then the fuse holder would have been carrying half this amount, ie around 200A. Does anyone think the 24v system is less safe?

Remember the power (heat) generated by the resistance in the fuse holder is dependent on the current squared. Reducing the current has a huge impact on the power (heat) that the fuse holder has to dissipate. A cooler fuse holder is a safer fuse holder.

[evm1024]

Originally Posted by noelex 77

I am not a fan of the 48v option. It is going to be difficult to find equipment to run on this voltage, and even small components such as many marine fuse holders are not suitable (often the limit is 32v).

This voltage also starts to present a shock hazzard. Over 50v can be fatal in the wrong circumstances. A salt water wet owner and boat is the wrong circumstance . A 48v battery system will be over 50v when charging. I am sure it could be made to work, and be safe, but not without significant effort. I think there would have to be a compelling reason, such an electric main engine, to justify using something different to almost every other yacht.

However, I think the suggestion that all higher voltages are inherently dangerous and increase the fire risk is also incorrect. A 24v house system does not decrease safety. I would argue that it is safer than a 12v system.

Let’s take a practical example recently reported on Cruisers Forum:

http://www.cruisersforum.com/forums/...ot-212632.html

This involved an ANL fuse holder overheating.

At 12v the fuse was carrying around 400A. If the boat had a 24V house bank then the fuse would have been carrying half this amount, ie around 200A. Does anyone think the 24v system is less safe?

Remember the power (heat) generated by the resistance in the fuse holder is dependent on the current squared. Reducing the current has a huge impact on the power (heat) that the fuse holder has to dissipate. A cooler fuse holder is a safer fuse holder.

Well said.

Perhaps this thread would be better served if the participants spent more time exploring how someone could implement a 48 volt system with the least risk.

I for one have learned from this thread. As KTP pointed out the Gigavac line has a number of higher DC voltage contactors that are useful in 48 volt applications.

GIGAVAC: ADVANCED SWITCHING SOLUTIONS - Contactors, High Voltage Relays, Switches, Power Products

Perhaps we can work toward designing a Right system rather than being Right.

[nebster]

I really doubt anyone is going to be running 48VDC all over the boat to every single load. That's a silly idea; there will always be the need for conversion (buck down, invert up) to more appropriate potentials. In the real world, our systems are heterogeneous.

Where 48V shines is in handling a big battery feeding a small handful of big DC loads. Those few can be carefully wired, fused, switched, and engineered for safety. It's easy to do, it's the only realistic option at many system sizes, and it's safer and less expensive than trying to mess around with 12V at enormous currents for a whole bunch of reasons.

Rod has made several valuable points (about 20 times, over and over) mixed in with some hyperbole and some flawed conclusions. Each of us should make sure we understand where exactly he is right and wrong, and why, before we go wire up a fresh 52VDC-nominal battery system.

[SilentOption]

If you said what kind of boat it is I missed it but If you ever intend to sell the boat you should really consider the financial impact of non-standard systems on resale. You might think 48 volts would be worth the effort but the next guy will have to take that on. You will have series parallel batteries, you will need dc to dc converters, and if you are rewinding motors you need to consider availability of spares. Starters come to mind.

[cj88]

I'm not that knowledgeable about electrics but hypothetically speaking if I decided to go with a 48v electric propulsion system using a bank of lithium batteries what would be best practice for a safe installation including powering the 12v house loads? Also, consider that based on posts in various threads by people about going electric it would include using such items as an induction cooktop and a microwave and/or convection oven along with standard items like nav gear, LED lighting, bilge pumps and an electric windlass. How would you build it?

[ramblinrod]

Originally Posted by cj88

I'm not that knowledgeable about electrics but hypothetically speaking if I decided to go with a 48v electric propulsion system using a bank of lithium batteries what would be best practice for a safe installation including powering the 12v house loads? Also, consider that based on posts in various threads by people about going electric it would include using such items as an induction cooktop and a microwave and/or convection oven along with standard items like nav gear, LED lighting, bilge pumps and an electric windlass. How would you build it?

There are likely as many different ways to do this as their are boaters.

If you are serious, I recommend consulting a local "certified" marine electrical professional (affectionately known as a "sparky").

A boater with a strong background in marine electrical technology, may wish to conduct all of the research themselves.

I still recommend they go over it with a sparky.

A good sparky may save you a ton of time, and far more in "mistake avoidance", than the cost of their consultation fee.

A good sparky brings a lot of education, training, skills, and experience to the table, that could take a lifetime to develop yourself, weeding through tons of good and bad info, trying to figure out which is which.

A good sparky will bring you up to speed very quickly on what you need to know to make sound, educated decisions.

[ramblinrod]

Originally Posted by nebster

Rod has made several valuable points...

Thanks for this statement.

If anyone wishes to discuss the 12 vs 24 vs 48 Vdc electrical system safety further, please click here to redirect to the new thread.

[Clipperau]

We have converted to 48 volt and love it. Run 48 wiring to stern midship and bow then drop down to 12v. A 20 amp drop down cost $15au so cost $45 for the 3 units. The effeciency gains far outweigh losses. A 12v fridge is designed to run @ 12v not 13v.
Use a 48v inverter to jump to 240v to run higher amp usage units like the microwave and coffee machine etc. Once again more effecient.
We have 1Kw solar to recharge.
Clipper is 28ft with 2.1m beam.

[waterman46]

Clipper, I don't doubt that you save a little on ohmic losses, but if you run smaller wire, then you may be right back to the same power loss you'd have in 12V conventional situation with proper wire size. For a 28 foot boat, the difference in cost for the larger required wire size would just about equal what you spent on the converters, with a bit better reliability of plain wire vs. the convertors.
BTW my "12V" equipment does run better on 13V, in all cases. More watermaker production, faster cooldown of freezer, etc.
Higher voltage may make some sense for a 55 footer, if there were no batteries for bow thruster and windlass already in the bow, but for a 28 foot boat, it seems a bit overkill. However one has to admire the uniqueness of this arrangement.
I am intrigued at how you can fit 1000W solar panels on your boat.

[Clipperau]

The 48v was needed as I run a 10Kw electric motor instead of a diesel and 8 AGM 200amp batteries.
Re the solar panels I suspended 2 160w as wings on the stanchions and 1 on a davit I made another 3 suspended using wire rope and Ball joint i devised on the rear stays.

[KTP]

Clipp, do you have a picture of that solar panel layout?

We also have a 10kW electric motor instead of diesel on a Pacific Seacraft 34 (also with a 48V bank of AGM). I am looking at the various ways to mount solar and yours sounds interesting. You must have a split back stay?

[Clipperau]

Yes, 2 back stays from the top of the mast rather than split. But does the same. Because I have a tiller over the stern I connected a as pipe with a ball joint at the top to experiment with being able to point the panels at the sun, to the stern rail parallel with the back stays to above the boom.
This acts as a mast, then using wire rope just with turnbuckles to tension and give some pointing adjustment just as the stays are there to take any forces from and give proper tension to the mast.
So far very stable and went out in 40knt winds and held very well.and not blown away.
Also gives shade and looking at fitting side tarps that can be pulled out port and Stb for more sun reliel
Clipper is a 50yo wooden Alan Buchannan.

[geoffa]

Originally Posted by ranchero76

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 went 48v high energy density lifepo4, 240v ac for majority house loads. 12v for standard boat dc circuits optimal. The 48v is 16 times less heating load on cabling, any higher cct breaker costs are high. 48v is the upper safe dc voltage, No current zeros. Use a 12v charger from the Ac cct for 12v when not running engine. This is a compromise as nothing is optimised however You can only use what the market provides. If I was Mr Tesla I would have a far more elegant solution.

[GordMay]

Greetings and welcome aboard the CF, Clipper.

[Clipperau]

Originally Posted by geoffa

I went 48v high energy density lifepo4, 240v ac for majority house loads. 12v for standard boat dc circuits optimal. The 48v is 16 times less heating load on cabling, any higher cct breaker costs are high. 48v is the upper safe dc voltage, No current zeros. Use a 12v charger from the Ac cct for 12v when not running engine. This is a compromise as nothing is optimised however You can only use what the market provides. If I was Mr Tesla I would have a far more elegant solution.

Optimising the Chas been the greatest challenge for us. We have the diesel away, no generator or access to shore power.
Our 1Kw of panels is split into 2 charging systems. The 20v wing panels are in paralell then boosted to 48v. I set them at an angle so that at least one panel is getting either morning or afternoon sun. Both generate during the day.
The 4 panels between the backstays are in series 80v and stepped down.
I found having more than one system allowed the panels to work more efficiently with the constantly changing sun facing angles.
I have 2 battery banks. Tesla is doing great bringing lithium battery prices down where I might be able to afford them shortly.