48V as main DC voltage on boat - anyone?

[StuM]

Originally Posted by witzgall

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

Care to explain that statement in terms of Ohm's Law?

[Dockhead]

Originally Posted by ranger42c

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.

-Chris

Indeed. RIGHT NOW is when you finally arrive in paradise, and you can't take a shower or wash a dish because your gray water pump is out and you can't find a spare. Or your windlass is out and you can't anchor anywhere. So instead of enjoying paradise, you spend the entire trip trying to solve the problem. Been there, done that, both examples, never again.

All this kind of stuff needs to be as common as possible, and backed up with spares of everything.

[rooiedirk]

My main battery is indeed 48V. But is only used for propulsion and the inverter(3kW)

Everything else is running via a 48/12V convertor. Yes your currents do increase, but all equipment is standard off the shelf.

Yes you can rewind the motor for a pump, but that makes it at least 3 times more expensive and it doesn't last longer.

[Jammer]

Originally Posted by witzgall

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.

Chris

There have been many discussions and plans over the years of higher voltages for automotive systems. For a while they were talking of an 84 volt system (3x the existing voltage of a 12 volt system but with recognition that the actual operating voltage of a 12 volt system is closer to 14 volts) but that was dropped on safety concerns. The main rationale was to be able to run more accessories with electric power rather than the engine. We've already seen a move from hydraulic to electric power steering, even with 12v. The air conditioning compressor would be another candidate.

Whether and when anything happens, and how much that will bleed over to marine applications, remains to be seen.

[Dave22q]

True 48 V system can use thinner wires. BUT everybody stocks 12 V appliances unlike 48 V ones.

[getyourbone]

To answer the original question...yes...kinda...

1983 Proust snow goose 37... I installed 48 volt battery modules to run refrigeration and charge some iPads/phones. 39 V solar panels run through a controller that boosts the voltage 50-ish volts. Simply used buck converters to drop it down to 12 V for any appliance connected. Thinking of changing the buck converter to 24 V as both the fridge in the freezer will handle that as well.

[witzgall]

Sorry, what I meant to say was that the awg size of wire needed for a given load (in watts) at 48v is 1/4 of that for 24v. Sunday morning...

Originally Posted by StuM

Care to explain that statement in terms of Ohm's Law?

[Redpcx]

I missed the point at first.
He is NOT asking if it is a good idea, or if it will save any money or if it will increase corrosion.
OF course it is more trouble than it is worth, and will cost more money at every step, and increase corrosion, and make the boat more difficult to service.
He just wants to know if anybody else has done it, and how they took care of some details. Possible, he is going for an electric drive?
I do strongly suggest you install wire that is large enough to handle the voltage that common in your area. Might be 12v in the US, might be 24v in Europe.
If it is to be insured, wire size could be a regulatory headache. Even if you are feeding your lights with 48 volts, don't reduce the wire size. Tiny wires are delicate!
When the boat is ever sold, the price WILL be reduced to change the electric stuff to normal, and if wire was sized for 48v, changing any wire that is hidden could have a remarkable effect on the value of the boat.

[mvmojo]

Originally Posted by Jammer

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.

DC current is extremely dangerous... and not just in terms of an electronic shock. 30 volts dc and above can stop your heart! This alone is enough reason to avoid >24vdc systems! If you have high power needs, why not just consider 120vac throughout and have a simple single battery 12v system for engine starting and bilge pumps. A relatively small 120vac to 12vdc power supply can run your electronics, and everything else can be ac, including your windlass.

[Wayfarer1008]

I hate to say in but the old mantra "keep it simple and keep it stupid" really needs to be followed when it comes to boat electronics. The more exotic and or more complicated you get the better the chance for breakdown at an inopportune moment.

[waterman46]

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!

Yep, that's insane. So most would simply run the generator when and if we ever needed large AC power. Maybe for a clothes dryer, electric stove, big SCUBA compressor or arc welder. Actually you won't be running that 3KW battery load very long anyway, unless you have a huge house battery bank.

Key to using any low voltage, high power equipment is to locate the batteries close to the application point. Starter battery close to motor, house battery close to invertor. That's why many larger boats have a dedicated battery forward for the anchor windlass.

Yes if you have electric winches then 24V makes sense. I would never use 48V - the deadly shock potential is just too risky.

[Cadence]

It sounds like an exercise in futility. If it were practical it would be an industry standard. There are to many items not available off the shelf that are 48V and transition would be price prohibitive. JMHO

[TrentePieds]

I think the more interesting question (than the one asked by the OP) is this:

What, precisely, apart from skinny wires, can the perceived incremental benefits of this higher voltage be for a mere yot?

All considerations taken together, I would think that such an "improvement" would make Willy Occam spin in his grave!

TP

[witzgall]

However, ABYC considers 48vdc (it might be 50v, I cannot recall) and under to be low voltage, and relatively safe. However, 48vdc nominal exceeds 50vdc easily, and this should require additional steps to be taken to ensure safe use on a boat.

Chris

Originally Posted by mvmojo

DC current is extremely dangerous... and not just in terms of an electronic shock. 30 volts dc and above can stop your heart! This alone is enough reason to avoid >24vdc systems! If you have high power needs, why not just consider 120vac throughout and have a simple single battery 12v system for engine starting and bilge pumps. A relatively small 120vac to 12vdc power supply can run your electronics, and everything else can be ac, including your windlass.

[Cadence]

Originally Posted by StuM

Care to explain that statement in terms of Ohm's Law?

I think he just got his #s turned around.

Not to be cruel, but sometimes a little bit of knowledge is dangerous.