Comparative Safety: 12v v 24v v 48

[ramblinrod]

Originally Posted by evm1024

One of the impediments to progress is thinking that the way we have done it in the past is the best and that there is not need to use other ways.

I couldn't agree more.

However, doing something different, just because it seems cool, can lead to total disaster.

Innovation is awesome, when done right, and for the right reason(s).

A 24 Vdc or 48 Vdc electrical system is not new technology; not by a long shot.

It is true, that today's boater demands electrical devices that consume more power.

When it makes sense to design a higher voltage electrical system, I will be the first to recommend it.

When it doesn't, I won't.

To increase system voltage, to reduce current, when there is no need, just to save a minimal amount of copper, is not adequate justification to reduce safety.

It's kinda like prepping the key market message for a new design, "New and improved cigarettes with twice the tar and nicotine, help you stand out in a crowd." (Image of a guy in the centre of 5 lung cancer patients speaking through their necks, in a designated smoking area, at the hospital.)

Some may jump all over this to be first to market.

I wouldn't.

[evm1024]

Originally Posted by ramblinrod

I couldn't agree more.

However, doing something different, just because it seems cool, can lead to total disaster.

Innovation is awesome, when done right, and for the right reason(s).

A 24 Vdc or 48 Vdc is not new technology; not by a long shot.

It is true, that today's market demands electrical devices that consume more power.

When it makes sense to design a higher voltage electrical system, I will be the first to recommend it.

When it doesn't, I won't.

To increase system voltage, to reduce current, when there is no need to reduce current, just to save a minimal amount of copper, is not adequate justification to reduce safety.

It's kinda like prepping the key market message for a new design, "New and improved cigarettes with twice the tar and nicotine, help you stand out in a crowd." (Image of lung cancer patients speaking through their necks, in a designated smoking area.)

Some may jump all over this to be first to market. I wouldn't.

Actually, It is clear that no one is really interested in your recommendations.

Wait lets count, Rod offering unwanted recommendations 25 times, number of times someone asks for Rod's recommendations 0.

[Dockhead]

Originally Posted by ramblinrod

. . . This commands a level or respect from the get go.

I have a very high respect for every engineer (until they give me cause to lower it, based on their behaviour or deliverables).

I have worked with engineers that I have held in very high regard, and I have worked with some that I have absolutely despised.

Similarly, I have worked with engineers who have despised me, for my audacity to stick my nose into their area of business, whereas I have worked with others who were astounded by my knowledge of complex concepts they barely "knew" themselves.

When a new engineer walks in the door, I have a certain degree of respect.

First of all, the general respect I have for all people, and then the respect I have for this individual for pursuing this career and achieving a level of success to date.

Now they have to show me what they can do and how they treat people along the way.

I will adjust my level of respect for them on this basis, mostly the latter.

If they are struggling with the technical complexity of their assignment, I can assign them to do something else, or assign another more knowledgeable or experienced in that particular issue to assist them.

But if they treat people poorly, they are soon an island, and out the door.

I think we might need a psychologist after all. What is all this about?


Why does any one have to show you anything ("now they have to show me what they can do")? What is the context of that? Why is "out the door" mentioned? So you hire engineers (never known an electrician who had engineers on staff, but whatever), and because you have the power to fire them, it means you think you know more than they do? This whole post is just weird.







We weren't talking about your personal relationships -- the suggestion was to respect the KNOWLEDGE of engineers. You argue with them aggressively on technical subjects at the center of their expertise.

Originally Posted by ramblinrod

When it makes sense to design a higher voltage electrical system, I will be the first to recommend it.

In other words, until Rod recommends it, it doesn't make sense to design higher voltage electrical systems? Do I understand this statement correctly?


I guess any engineers who disagree will be "out the door"?




I think this may qualify as a "delusion of grandeur".

Originally Posted by ramblinrod

whereas I have worked with others who were astounded by my knowledge of complex concepts they barely "knew" themselves.

Therefore, we should believe that you understand engineering concepts better than real engineers. Okaaaayyyy . . . . .

[Dockhead]

Originally Posted by evm1024

You have made some really great points here that are really worthwhile. This is especially true for anyone who is contemplating new design.

One of the impediments to progress is thinking that the way we have done it in the past is the best and that there is not need to use other ways. Of course those ways are comfortable and comforting and low risk. This is especially true if you make your living based on those ways. This resistance to change, mental inertia takes many forms. Lithium - not needed, Lead (and ICE) does it all. 48 volts - danger, danger Will Robinson.

But with those old ways you never get the leaps of performance.

Well, I'm actually quite conservative.


I develop and build buildings in my day job these days, so deal with design issues, including electrical design issues, every day. I have tremendous respect actually for the "old ways", or at least those ways which are "old" enough to have been proven with practical experience and which are backed up by a certain amount of R&D.



I love technology and it is fascinating to think about it, but I try not to get carried away with it.


So it took me a really long time, for example, to come around to understanding that lithium for cruising boats is actually really ready for prime time. I was probably excessively conservative about that.


But lithium really is ready for prime time, and the next boat will be designed from the ground up for lithium. Lithium power is so different, that it begs for other changes of architecture. It allows a different approach to power generation, one which might dispense with the heavy duty generator. The whole layout and approach of the system needs to be different, and a 48v backbone seems to make eminent good sense.






But although I love thinking about design and engineering and jawboning about it on here, I will not be designing the next boat myself, any more than I would design one of my own buildings myself. The next boat will be designed by a proper professional design team, including a top-notch electrical engineer (I learned years ago that with any project, in trying to control costs, save money on absolutely anything, EXCEPT design). I will not interfere in their work with my own amateurish ideas, other than to give them an extremely detailed design brief describing very precisely how I want the boat and all of her systems to perform. One of the points in the design brief is that the electrical system has to be extremely reliable, extremely serviceable, and extremely safe. I will trust in the engineer to realize those values in an optimum way, considering how I will be using the boat.


But the jawboning is FAR from a waste of time. Because design is a recursive process -- you can't write the brief, if you don't understand what is possible at the current state of the art. So I'm extremely grateful for the wealth of knowledge on this forum, so generously shared.

[Q Xopa]

Originally Posted by ramblinrod

Careful, or that could be your new moniker.... [emoji3]

Hmm, If I were a betting man, hes not the one I would be putting my money on for the popular vote for that moniker.

[Q Xopa]

I dont know if you missed the previous links to the Automotive industry moving to 48, or maybe it was 42V (cant remember the exact specifics) in the next few years.

They must be throwing safety and switch reliability out the window?

What are they thinking? I guess profit margins rule?

Are you going to still be recommending 12V systems when newer alternators etc are higher voltages?

Just wondering.

[Steve_C]

Originally Posted by Dockhead

What kind of high power gear do you have on board? How large a vessel?

I am currently about a year or two away from my next vessel, working on retirement and caring for my 91 year old dad! I am more or less finalizing what I truly need and want. I am focused on a Cat from 40 to 45 feet. I will start shopping in earnest soon because it will likely take me a while to find what I want at the price I like I have already begun preparing to sell off my home and start the process.

Gear
Induction Cooktop - Microwave - Electric Oven
Electric Grill - (Probably Weber Q 2400)
AC (AirCond.) - for at the Dock or a few hours in the evening

These would definitely be AC - Probably 220 - 50 Hz


Water Maker
Scuba Compressor

These could potentially be AC or DC - This would probably be a great candidate for 48 V DC??? However if I have a large AC inverter would I be better off with this being AC?? It would also be interesting if I could find and use the same motor for each, to give me better backup/emergency options.


and off course Winches and Windlass - DC - Voltage - TBD

Originally Posted by Dockhead

Large 48 volt alternator charging a large 48v lithium bank powering a 48v inverter bank is very straightforward and deals with the large power involved, knocking down the large currents. From what the engineers are saying, and you be one yourself I guess, that would seem like a superior and generally safer solution. But what kind of high power gear do you have? 48v thrusters exist, but I'm not sure less then 15hp. 48v windlasses exist. I don't know about winches or furlers, but those use fairly generic motors, so you could probably change or rewind the motors if you had to.

I have conflicting feelings about the Windlass and/or Winches. While I am not the least bit afraid of 48 volt for this application, I will be travelling in many remote areas and if I will already have a 12 or 24 Volt small bank for other loads I may be better off with that. the winches would need to be either rewound or have motors replaced, and the Windlass is somewhat in the same category. I don't want to just use 48V just for the sake of it, in these applications, if there is no real advantage. KISS

Originally Posted by Dockhead

If you can get your high power gear in native 48v, then it would be pretty straightforward to use a small 12v or 24v bank for all the non-high power gear, with separate switch panels and busses. Charge via battery-to-battery charger. This is the very architecture I'm considering for my next boat. Small increase in complexity but then you gain backup power.

My present boat has 2x completely separate 12v engine control and starting systems, each with its own alternator, plus 1x 24v system with own large frame heavy duty alternator for house and technical loads. Seems like an absolutely reasonable approach, and I don't see why you couldn't do something similar with 48v and 12v. No need for droppers; just separate the systems with own small battery bank for the 12v (and/or 24v) system(s).

Agree totally, but can I get by with just 24V? or would just 12V be advantageous????

Originally Posted by Dockhead

I think your idea of eliminating the generator and using a very large 48v alternator on the main engine is a good one. Many systems design arguments for that. Getting rid of the generator saves huge weight, volume and cost. My next boat will be designed for extreme latitudes and extremely remote places, and so needs extreme reliability and redundancy, so I won't get rid of the generator, but I might have just a small emergency generator (NexGen or something like that), rather than a half-tonne heavy duty low-speed prime power rated one like what I have now. With primary generation just like what you're considering.

This is exactly what I am thinking, get rid of the large heavy generator. With two main propulsion engines and high output capacity on both I can have plenty of redundancy. Along with a very large Solar array (Probably at least 2KW) And a LFP capacity of at least 1600AH @ 12V (or 400AH @ 48V) or larger I should be good. Your "extreme reliability and redundancy" is my goal as well.

Having witnessed extreme faults at both high current AND high voltage (One time was 400 amps @ 2400 Volts) I am probably a bit extreme about circuit safety and protection. I have absolutely no concerns about doing this safely. However, any system at ANY voltage at this capacity needs to be designed by someone who truly understands all of the implications of component decisions. No matter how qualified someone is, I prefer to have multiple qualified engineers review and look for problems and/or suggestions for improvements. Safety trumps pride every time!!!!!!!!!

[CatNewBee]

If you buy pre-owned, I would first check what is installed and what needs replacement and then look for the best solution. Most production cats are 12V + 240V or 12V +110V. If you have power winches and all this in 12V it would be a huge investment to replace by 24V or more or you have to run a separate 12V installation on top, what makes it even more complicated.

But if you need to replace the whole electric anyway or plan new, you can take what you prefer I guess.

My refit was driven by using and leveraging what was there, so I stuck at 12V.

[Steve_C]

Originally Posted by CatNewBee

If you buy pre-owned, I would first check what is installed and what needs replacement and then look for the best solution. Most production cats are 12V + 240V or 12V +110V. If you have power winches and all this in 12V it would be a huge investment to replace by 24V or more or you have to run a separate 12V installation on top, what makes it even more complicated.

But if you need to replace the whole electric anyway or plan new, you can take what you prefer I guess.

My refit was driven by using and leveraging what was there, so I stuck at 12V.

Yes, In all likelihood I will be buying used. Very possibly a L400 just like you. Depends on how I do setting up my retirement income in the next year or so

I highly suspect I would stick with 12V for the winches and windlass. I will likely be shopping in the Med so the AC will just depend on what I find. I am still thinking 48V may be the way to go for the main House Bank

[Dockhead]

Originally Posted by Steve_C

I am currently about a year or two away from my next vessel, working on retirement and caring for my 91 year old dad! I am more or less finalizing what I truly need and want. I am focused on a Cat from 40 to 45 feet. I will start shopping in earnest soon because it will likely take me a while to find what I want at the price I like I have already begun preparing to sell off my home and start the process.

Gear
Induction Cooktop - Microwave - Electric Oven
Electric Grill - (Probably Weber Q 2400)
AC (AirCond.) - for at the Dock or a few hours in the evening

These would definitely be AC - Probably 220 - 50 Hz


Water Maker
Scuba Compressor

These could potentially be AC or DC - This would probably be a great candidate for 48 V DC??? However if I have a large AC inverter would I be better off with this being AC?? It would also be interesting if I could find and use the same motor for each, to give me better backup/emergency options.


and off course Winches and Windlass - DC - Voltage - TBD



I have conflicting feelings about the Windlass and/or Winches. While I am not the least bit afraid of 48 volt for this application, I will be travelling in many remote areas and if I will already have a 12 or 24 Volt small bank for other loads I may be better off with that. the winches would need to be either rewound or have motors replaced, and the Windlass is somewhat in the same category. I don't want to just use 48V just for the sake of it, in these applications, if there is no real advantage. KISS




Agree totally, but can I get by with just 24V? or would just 12V be advantageous????





This is exactly what I am thinking, get rid of the large heavy generator. With two main propulsion engines and high output capacity on both I can have plenty of redundancy. Along with a very large Solar array (Probably at least 2KW) And a LFP capacity of at least 1600AH @ 12V (or 400AH @ 48V) or larger I should be good. Your "extreme reliability and redundancy" is my goal as well.

Having witnessed extreme faults at both high current AND high voltage (One time was 400 amps @ 2400 Volts) I am probably a bit extreme about circuit safety and protection. I have absolutely no concerns about doing this safely. However, any system at ANY voltage at this capacity needs to be designed by someone who truly understands all of the implications of component decisions. No matter how qualified someone is, I prefer to have multiple qualified engineers review and look for problems and/or suggestions for improvements. Safety trumps pride every time!!!!!!!!!

You should ask whoever you hire to design your system, but the advantages of a 48v "backbone", to me, start to disappear if you are using high power equipment of a different voltage. Depending I guess on how you feel about using a large dropper to power high power equipment like a windlass.



On the other hand, droppers, although they eat some power, DO have a certain advantage in that they regulate voltage and may largely prevent any voltage drop at all. Interesting to think whether that might even be worth everything else.



With a cat, I guess you won't have a bow thruster?



And of course, 24v does work OK, you will just be managing rather big currents between alternator and lithium bank and inverters, and your lithium bank will need cells twice the size. At least with lithium you are unlikely to need to parallel them, and even if you do, there are not the problems we have with paralleling lead, since with lithium we have BMS to do the balancing.


Just one amateur's view -- consult an actual engineer when you get closer to pulling the trigger!!

[ramblinrod]

Originally Posted by Dockhead

We weren't talking about your personal relationships -- the suggestion was to respect the KNOWLEDGE of engineers.

Oh, now I see.

Should I bow or courtesy?

I do, in general, respect the "potential" knowledge of engineers (and all professions) but as I mentioned, and another poster so aptly stated, that respect has to be earned and maintained.

It is very hard to respect the opinion of those who claim to be experts, yet have made so many fundamental mistakes, around such basic principles as Ohm's Law and Watt's Law.

Go back through the posts.

Look at all of the corrections I made.

Every one of them is accurate, based on fundamental principles, with practical examples given to demonstrate veracity.

You are correct; the subject isn't that complicated.

Yet those who apparently should be respected because of their parchment, were making basic, basic, errors on matters central to their education.

You argue with them aggressively on technical subjects at the center of their expertise.

If "arguing aggressively" is defined as "politely stating disagreement, and supporting that with facts and examples", and not being stifled or shunned by continuous disrespectful backlash, I guess you are correct.

In other words, until Rod recommends it, it doesn't make sense to design higher voltage electrical systems? Do I understand this statement correctly?

No.

Now even you are relying on strawman arguments.

I never claimed this.

I am asked for my recommendations on vessel design and modification matters on a daily basis.

I have already clearly indicated, many times, that I have no problem using a higher electrical system voltage, WHEN IT IS WARRANTED.

Why are you attempting to claim my position is that higher voltage is bad in all cases? That's not true. It is potentially more dangerous, but sometimes this must be accepted for the gain in potential benefit.

But when not required, and where the danger outweighs the benefit, who in their right mind would recommend it?

I don't recommend what I don't believe is a good idea, based on my knowledge and experience.

huh.

whodathunkit.

I am trying to contribute to the forum in a meaningful and useful way, but you and some others are trying to make that impossible, without an incredible barrage of personal, humiliating attacks, if my position contradicts theirs.

Insecurity I guess.

This is not the way to convince me to be more respectful of your parchments.

I guess any engineers who disagree will be "out the door"?

What are you talking about???

I was referring to engineers assigned to a product development team.

They can disagree with me all they wish.

But then if they can't deliver, and they can't get along with others because of their pompous and arrogant attitude of superiority, they're gone; they serve no purpose to the organization.

The ones who have personal integrity, work well with others, and can contribute in a meaningful way to the team, are more than welcome to stay, they are paid handsomely to do so.

That simple.

Therefore, we should believe that you understand engineering concepts better than real engineers. Okaaaayyyy . . . . .

Engineering is not my primary focus.

It could have been if I so desired.

Still, there have been cases (actually many) where I have understood concepts and principles better than a "real engineer"; this thread is a prime example.

Note the number of "corrections" I posted to invalid statements made by some of them.

Every one of those corrections was based on sound scientific and engineering principles.

Anyone can duplicate the examples I used and produce the exact same results.

As well as working with many engineers I have admired and respected, I have also seen my share of total idiots.

Perhaps the finest example was the day I observed an "engineer" performing a Hipot test on a nuclear power station electrical panel, "light up" our CEO in the middle of a dignitary tour of the facility, immediately after being introduced to the group, and advised they were conducting a tour of the area.

How much respect should that kind of move garner?

If these strawman arguments and this kind of continued personal attack is what they teach in university, "How to defend flawed positions when challenged by someone with lesser education", well, I am even more profoundly happy that I chose not to pursue a degree in a grotesquely flawed institution, in order to gain my useful knowledge and experience in the real world, where it counts.

[ramblinrod]

Originally Posted by Q Xopa

Australian's have a term of enderment for these particulrly knowledgable individuals- 'FIG JAM's (F... Im Good, Just Ask Me).

Not worthy.

[ramblinrod]

Originally Posted by Steve_C

I am currently about a year or two away from my next vessel, working on retirement and caring for my 91 year old dad! I am more or less finalizing what I truly need and want. I am focused on a Cat from 40 to 45 feet. I will start shopping in earnest soon because it will likely take me a while to find what I want at the price I like I have already begun preparing to sell off my home and start the process.

Gear
Induction Cooktop - Microwave - Electric Oven
Electric Grill - (Probably Weber Q 2400)
AC (AirCond.) - for at the Dock or a few hours in the evening

These would definitely be AC - Probably 220 - 50 Hz

Water Maker
Scuba Compressor

These could potentially be AC or DC - This would probably be a great candidate for 48 V DC??? However if I have a large AC inverter would I be better off with this being AC?? It would also be interesting if I could find and use the same motor for each, to give me better backup/emergency options.

and off course Winches and Windlass - DC - Voltage - TBD

I have conflicting feelings about the Windlass and/or Winches. While I am not the least bit afraid of 48 volt for this application, I will be travelling in many remote areas and if I will already have a 12 or 24 Volt small bank for other loads I may be better off with that. the winches would need to be either rewound or have motors replaced, and the Windlass is somewhat in the same category. I don't want to just use 48V just for the sake of it, in these applications, if there is no real advantage. KISS

Agree totally, but can I get by with just 24V? or would just 12V be advantageous????

This is exactly what I am thinking, get rid of the large heavy generator. With two main propulsion engines and high output capacity on both I can have plenty of redundancy. Along with a very large Solar array (Probably at least 2KW) And a LFP capacity of at least 1600AH @ 12V (or 400AH @ 48V) or larger I should be good. Your "extreme reliability and redundancy" is my goal as well.

Having witnessed extreme faults at both high current AND high voltage (One time was 400 amps @ 2400 Volts) I am probably a bit extreme about circuit safety and protection. I have absolutely no concerns about doing this safely. However, any system at ANY voltage at this capacity needs to be designed by someone who truly understands all of the implications of component decisions. No matter how qualified someone is, I prefer to have multiple qualified engineers review and look for problems and/or suggestions for improvements. Safety trumps pride every time!!!!!!!!!

When the time comes, send me a PM; I will help review your needs and recommend solutions that will meet your performance expectations, while being reliable, safe, and economically justifiable.

[Q Xopa]

Originally Posted by ramblinrod

Not worthy.

Correct, but you did anyway.

Anyway, carry on. Was someone saying something about everyone else being wrong or something.

[ramblinrod]

Originally Posted by CatNewBee

If you buy pre-owned, I would first check what is installed and what needs replacement and then look for the best solution.

Valid approach.

Most production cats are 12V + 240V or 12V +110V. If you have power winches and all this in 12V it would be a huge investment to replace by 24V or more or you have to run a separate 12V installation on top, what makes it even more complicated.

Agreed.

But if you need to replace the whole electric anyway or plan new, you can take what you prefer I guess.

Of course.

My refit was driven by using and leveraging what was there, so I stuck at 12V.

Absolutely!

If 12 Vdc was perfectly adequate to meet your needs, and not sub-optimal to any real extent, to do otherwise would be a total waste of time, effort, and money for no benefit, other than the experience of performing unnecessary, expensive modifications.