Comparative Safety: 12v v 24v v 48

[Dockhead]

Originally Posted by ramblinrod

. . . 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.

. . .

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

To the half knowledgeable but lay mind, at least to this one, it did not look like the engineers were making fundamental mistakes at all. I don't think anyone made any mistakes in Ohm's law -- even I understand that much. The argument looked to me like, on the contrary, that they were correcting incorrect blanket statements (for example, "danger is proportional to voltage", which seems really totally wrong to me, and worse than an oversimplification, and which you kept repeating over and over again) based on what looks to me like a shallow understand of the underlying electrical engineering principles, with a deeper engineering analysis of the issues. For example -- that the resistance of a bad connection can't be treated simply like a heater. Or that 10 ohms is very unlikely to be the actual resistance value. Or that you can't consider voltage without current. Etc. etc. etc. Accusing experienced professional electrical engineers of misunderstanding Ohm's law just looks ridiculous and actually discredits everything else you say.



To me it looked like instead of engaging these arguments, you kept just thunderously insisting on your own conclusions based on your own rules of thumb, getting offended when no one accepted them just because they are "something I've known for 40 years".

Originally Posted by ramblinrod

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.. .

There was offense and acrimony, and that is unfortunate. "Push back" occurs when you insist on your own conclusions, based on your own authority, which you think everyone should accept. Some of that push back surely should have been more respectful, but why do you think you always get this reaction? You told a professional engineer to "go to an Introduction to Electricity class" -- what do you expect?




A lively discussion on something people disagree about, is the heart and soul of this forum. Without disagreement, there would be no learning. But for this to result in a useful conversation, you have to be ready for disagreement, and you have to be ready with something besides appeals to your own authority, in case people don't agree with your technical analysis. And here no one expects a great sparky, to know more than good electrical engineers -- they're different jobs. The engineers would probably be horrible at what you (or I) do; there's no need to be ashamed of that. That doesn't mean you can't argue with them on engineering questions, but Jesus -- telling them to go to an "Introduction to Electricity class"? And then going on yourself, about your own "astounding" knowledge: "I have worked with engineers . . . who were astounded by my knowledge of complex concepts they barely 'knew' themselves." That is a gross overreach. At that point, push back, turns into ridicule. And that's why I was suggest a little respect for their knowledge -- have a glimmer that in years of study, and decades of practice, they might know something about it, which you don't.



Sorry to say all of this, but it is said in a sincere attempt to help you get more out of these discussions, and be less often offended.

[Steve_C]

Honestly the fundamental architecture will be finalized once I actually own the vessel and will be driven primarily by the existing equipment and the charging system (from the engines) that works best. My main areas of concern are the alternators(generator?), and the main house bank to the invertor. These are the highest load connections and deserves due consideration.
I am intrigued by the integral system and will anxiously await real world feedback. I am sure more high output options like this will be offered in the near future. Certainly 24V output is an option, I just cannot stop myself from considering all options.
I am sure if I just think about it long enough I will find a much better way than anyone ever thought of before,,,,right 🤩[emoji51]

[evm1024]

Originally Posted by Steve_C

Honestly the fundamental architecture will be finalized once I actually own the vessel

SNIP

Sounds like a plan. In the design stages your best bet (I'm sure you know all this...) would be to hook up with a design engineer with experience in the type of design you are contemplating.

Even if you were a design engineer I expect you would want to run the design past another qualified engineer.

It is our good fortune to have a few of those on CF that you might try contacting if you have not. Mainesail comes to mind as does Bruce Schwab.

Actually Bruce has commented in the parent thread to this thread. Here are two quotes:

Originally Posted by OceanPlanet

Speaking of 48V serial-hybrid electric systems, with 12V system battery backup...here is a system for a charter cat being done currently.

Originally Posted by OceanPlanet

MOST of the larger yacht systems we do are now 24V, not 12V Sometimes there is a small backup 12V battery to keep the 12V nav or lighting running in the case of a main bank LVC.

You will soon see more high-performance yachts going 48V (actual nominal for Li systems will be 51V) for the charging & batteries, as it is considerably more efficient and less weight. One example of the charging efficiency: A 28V x 185A American Power HPI alternator is cold-rated at 185A, and the same size unit in 56V is cold-rated at 150A. If hot outputs are 80% (usually are more, however for calculation purposes) that's 4.1kW for the 28V and 6.7kW for the 56V. Note that I'm using actual charging voltages vs. nominal.

Anyhow, that's at least 50% more output in kW, from the same size alternator, through cables that are 1/2 the weight. The inverter conversion efficiency to the AC loads is also more efficient at the higher DC voltage.

Note that residential energy storage is already going to much higher DC voltages (288V to 360V), for the same gains in efficiency. However that level would not be very safe on a boat...

When you get to the actual installation if you do not do it yourself you local friendly marine surveyor is your friend. They will be able to recommend an installation tech. In general the surveyor knows who does a good job and who does not. The surveyor a few slips down from me says that most of the certified tech are marginal at best and some are dangerous. Lots of rework. But, a few shine.

Oh one more thing. There are many types of ABYC certifications. At a base level an ABYC Certified Marine Systems tech studied and took a test of around 200 questions that covered 12 or more sets of marine topics. The actual number of questions on Marine Electrical is quite small.

On the other hand an ABYC Certified Marine Electrical tech studied and took a test with around 200 questions on marine electrical.

Stick with the ABYC Certified Marine Electrical tech for your install.

Lastly there is the compatibility factor - but that is a very individual thing.

[ramblinrod]

Originally Posted by evm1024

Oh one more thing.

So sayeth the one with no ABYC membership or certification at all. ;-)

Exactly what kind of marine service do your provide?

[ramblinrod]

Originally Posted by Dockhead

To the half knowledgeable but lay mind, at least to this one, it did not look like the engineers were making fundamental mistakes at all.

This is why one has to be oh so careful what information they accept as valid.

You have accepted information as valid, because it appeals to your layman perspective, not because it is accurate or true, and in this case, it wasn't.

I don't think anyone made any mistakes in Ohm's law -- even I understand that much.

Apparently not, 'cause, yup they did, many times, the reason I repeated it over and over, after most of the occurrences I encountered.

The argument looked to me like, on the contrary, that they were correcting incorrect blanket statements (for example, "danger is proportional to voltage"....

Interesting that I have proven with scientific evidence many times throughout this post, that the statement is true "barring any mitigating factors".

One poster correctly identified that all electrical systems are dangerous.

The potential for an electrical system short circuit exists in every vessel (that has one).

The risk of danger from a short circuit, increases with system voltage "barring any mitigating factor".

I am sorry if you have some kind of unwarranted phobia about general statements, never-the-less, the assertion is true, and I have proven it with scientific evidence and examples that can be repeated by anyone, who will realize the same results.

I'm also sorry if you expected it to be more complicated.

It isn't.

Maybe you just can't believe that supposed experts could make such fundamental mistakes, due to a belief that to err is human but not if one is an engineer. Sorry to rattle your world; they are human too,

which seems really totally wrong to me, and worse than an oversimplification, and which you kept repeating over and over again) based on what looks to me like a shallow understand of the underlying electrical engineering principles, with a deeper engineering analysis of the issues.

So this is an apparent misperception.

I repeated the corrections over and over again in response to those who shouldn't be, repeating the same mistakes over and over again.

It wasn't due to shallowing understanding of any principles on my part.

My understanding is plenty deep enough; it was due the errors being made on such fundamental principles by others.

For example -- that the resistance of a bad connection can't be treated simply like a heater.

Who claimed that?

Not me.

A purely resistive load can act exactly like a heater, because quite frankly, a heater is an example of a purely resistive load.

I've always known that.

I have no idea what you are talking about.

Or that 10 ohms is very unlikely to be the actual resistance value.

Are you referring to the argument by a non-engineer that there cannot possibly be 10 ohms of resistance between two contacts because they could not find (after who knows what type of search) any scientific paper indicating that this could be so?

And then tried to imply that if I would not waste my time searching for a scientific paper to prove my assertion based on fundamental and sound engineering principles, that this somehow proved their flawed assertion correct?

That's just another example of flawed logic.

I'm not going to waste any time on that.

Don't be ridiculous.

I know that it is unlikely for a "good" contact to be 10 ohms.

They are usually in the order of milliohms.

In a bad contact, as I correctly stated, there can be any resistance between two contact surfaces from near zero to near infinity and anything in between.

10 ohms is certainly plausible.

Or that you can't consider voltage without current. Etc. etc. etc.

Strawman Alert:

I never claimed that.

With any general statement, it is implied to include the concept, "barring any mitigating factors" (BMF).

Of course if there is something that could skew the normal cause / effect, that will have an impact.

It does not invalidate the underlying principle.

Especially, when it is extremely plausible, that there may be no mitigating factors at play, or we don't know if there will be in the instant circumstance.

Many of what you refer to as corrections to my statements, were not corrections, they are either fundamental misunderstandings on the part of the other poster, or the application of mitigating factors that could be at play, but also may not, and in many cases, aren't.

I was the one that clearly and correctly indicated that the potential current in a circuit is governed by Ohms law (BMF).

If the resistance is fixed and the voltage increases, so must current (BMF).

I also correctly indicated that the potential energy of a circuit is governed by Watts Law (BMF).

If the resistance is fixed, and the voltage is increased, the energy dissipated necessarily increases (BMF).

I am sorry if you want the relationships to be more complicated; they simply aren't.

Accusing experienced professional electrical engineers of misunderstanding Ohm's law just looks ridiculous and actually discredits everything else you say.

Strawman Alert:

I didn't.

I advised them their assertions were incorrect, because they failed to apply Ohm's and Watt's Laws, which proved there assertions invalid.

To me it looked like instead of engaging these arguments, you kept just thunderously insisting on your own conclusions based on your own rules of thumb, getting offended when no one accepted them just because they are "something I've known for 40 years".

Gimme a break.

If you had knowledge, that proved itself consistently, based on 40 years of education, training, and experience, and sound underlying principles of physics, and someone (who often makes gross errors) claimed a principle based on that knowledge incorrect, using flawed logic and no evidence, would you suddenly discard your long held understanding and accept theirs, despite knowing it to be wrong?

You can if you wish, but please rest assured, I will not.

There was offense and acrimony, and that is unfortunate.

If someone gets offended when another politely points out their error, especially when in response to their contradictory incorrect statements, well, that is their weakness.

"Push back" occurs when you insist on your own conclusions, based on your own authority, which you think everyone should accept.

I did no such thing.

I posted irrefutable facts and examples based on them.

Some of that push back surely should have been more respectful, but why do you think you always get this reaction?

Yes, in my opinion, many of those posts violated forum rules, and should not be allowed.

It has been disappointing from my perspective and detracts from the value of this medium.

I am sure some would have expressed support for my contributions but did not for fear they would be retaliated against like I have been.

You told a professional engineer to "go to an Introduction to Electricity class" -- what do you expect?

I don't believe I stated any such thing to any P. Eng.

I told a person of limited knowledge of marine electrical systems, based on a large number of gross errors they were making in their assertions and contradictions to my valid statements, that they should take such a class. I believe it would help them.

I have provided training for engineers for many years.

It has been my professional responsibility to evaluate knowledge gaps and recommend training solutions, for people in engineering positions.

I don't think the person you are referring to is an engineer at all.

A lively discussion on something people disagree about, is the heart and soul of this forum.

I don't mind disagreement.

I'm just getting sick and tired of the barrage of intentionally humiliating insults when I politely disagree with someone.

I've never cowered from a cyber bully, so I don't back down (which is obviously their desired outcome) while I try to take the high road, to the extent possible.

I have very thick skin, but sooner or later, one can only get away with poking a bear so many times.

Occasionally they may wear me down a bit, and I may sound less cordial after their repeated pokes. It is sad that I have to endure that or just let their erroneous comments stand uncontested.

Without disagreement, there would be no learning. But for this to result in a useful conversation, you have to be ready for disagreement, and you have to be ready with something besides appeals to your own authority, in case people don't agree with your technical analysis.

I am ready for disagreement, obviously. I have politely posted evidence, when warranted, to support my disagreement many, many, times.

And here no one expects a great sparky, to know more than good electrical engineers -- they're different jobs.

I agree completely, which makes it so surprising about the number of gross errors I have corrected.

The engineers would probably be horrible at what you (or I) do; there's no need to be ashamed of that.

Correct.

I know full well one should never hire an engineer to perform a technicians job.

I have seen the fall out from this, many, many times.

have a glimmer that in years of study, and decades of practice, they might know something about it, which you don't.

I do expect this.

This is why I was so dumbfounded, by the gross errors being made.

Sorry to say all of this, but it is said in a sincere attempt to help you get more out of these discussions, and be less often offended.

Thanks, but I am not really offended, by those who attempt to make offending posts when I try to correct them.

I detest there offensive post.

I think it detracts from the value of the forum.

But if it's allowed, what should I do, discontinue correcting misinformation?

If everyone did that, this forum would have no useful information at all, or at least no one with lesser understanding to gain better understanding.

The evidence is right here, that you swallowed a hole can of worms of misinformation hook, line, and sinker, because you trusted that information posted by others, would be true, and it sounded plausible to you, when it really wasn't correct, but you mistrusted my corrections because you incorrectly assumed the matter must be more complex, such that one who is not an engineer, could not possibly be correct in their continued attempts to reduce the misinformation proliferation.

[CatNewBee]

Originally Posted by ramblinrod

This is why one has to be oh so careful what information they accept as valid.

You have accepted information as valid, because it appeals to your layman perspective, not because it is accurate or true, and in this case, it wasn't.



Apparently not, 'cause, yup they did, many times, the reason I repeated it over and over, after most of the occurrences I encountered.



Interesting that I have proven with scientific evidence many times throughout this post, that the statement is true "barring any mitigating factors".

One poster correctly identified that all electrical systems are dangerous.

The potential for an electrical system short circuit exists in every vessel (that has one).

The risk of danger from a short circuit, increases with system voltage "barring any mitigating factor".

I am sorry if you have some kind of unwarranted phobia about general statements, never-the-less, the assertion is true, and I have proven it with scientific evidence and examples that can be repeated by anyone, who will realize the same results.

I'm also sorry if you expected it to be more complicated.

It isn't.

Maybe you just can't believe that supposed experts could make such fundamental mistakes, due to a belief that to err is human but not if one is an engineer. Sorry to rattle your world; they are human too,



So this is an apparent misperception.

I repeated the corrections over and over again in response to those who shouldn't be, repeating the same mistakes over and over again.

It wasn't due to shallowing understanding of any principles on my part.

My understanding is plenty deep enough; it was due the errors being made on such fundamental principles by others.



Who claimed that?

Not me.

A purely resistive load can act exactly like a heater, because quite frankly, a heater is an example of a purely resistive load.

I've always known that.

I have no idea what you are talking about.



Are you referring to the argument by a non-engineer that there cannot possibly be 10 ohms of resistance between two contacts because they could find (after who knows what type of search) any scientific paper indicating there could be?

That's just false.

It is unlikely for a good contact to be 10 ohms. They are usually in the order of milliohms.

In a bad contact, as I correctly stated, there can be any resistance between two contact surfaces from near zero to near infinity and anything in between.

10 ohms is certainly plausible.



Strawman Alert:

I never claimed that.

With any general statement, it is implied to include the concept, "barring any mitigating factors" (BMF).

Of course if there is something that could skew the normal cause / effect, that will have an impact.

It does not invalidate the underlying principle.

Especially, when it is extremely plausible, that there may be no mitigating factors at play, or don't know if there will be in the instant circumstance.

Many of what you refer to as corrections to my statements, were not corrections, they either fundamental misunderstandings, or the application of mitigating factors that could be at play, but also may not, and in many cases, aren't.

I was the one that clearly and correctly indicated that the potential current in a circuit is governed by Ohms law (BMF).

If the resistance is fixed and the voltage increases, so must current (BMF).

I also correctly indicated that the potential energy of a circuit is governed by Watts Law (BMF).

If the resistance is fixed, and the voltage is increased, the energy dissipated increases (BMF).

I am sorry if you want the relationships to be more complicated; they simply aren't.



Strawman Alert:

I didn't.

I advised them their assertions were incorrect, because they failed to apply Ohm's and Watt's Laws, which proved there assertions invalid.



Gimme a break.

If you had knowledge, that proved itself consistently, based on 40 years of education, training, and experience, and sound underlying principles of physics, and someone (who often makes gross errors) claimed a principle based on that knowledge incorrect, using flawed logic and no evidence, would you suddenly discard our long held understanding and accept theirs, that you knew to be wrong?

Actually, don't answer that. According to this post, I guess you would. (BTW, that does not make them or you correct.)



If someone gets offended when another points out their error, especially when they are contradicting correct statements, well, that is their weakness.



I did no such thing.

I reported irrefutable facts and examples based on them.



Yes, in my opinion, many of those posts violated forum rules, and should not be allowed.

It has been disgusting and detracts from the value of this medium.

I am sure some would have expressed support for my contributions but did not for fear they would be retaliated against like I have been.



I don't believe I stated any such thing to any P. Eng.

I told a person of limited knowledge of marine electrical systems, based on a large number of gross errors they were making in their assertions and contradictions to my valid statements, that they should take such a class.

I have provided training for engineers for many years.

It has been my professional responsibility to evaluate knowledge gaps and recommend training solution, for people in engineering positions.

I don't think the person you are referring to is an engineer at all.



I don't mind disagreement.

I'm just getting sick and tired of the barrage of intentionally humiliating insults when I politely disagree with someone.

I've never cowered from a bully, so I tend to go toe to toe with them, trying to take the high road, wherever possible.

Occasionally they may wear me down a bit, and I may sound less cordial after their repeated attacks.

Without disagreement, there would be no learning. But for this to result in a useful conversation, you have to be ready for disagreement, and you have to be ready with something besides appeals to your own authority, in case people don't agree with your technical analysis.



I agree completely, which makes it so surprising about the number of gross errors I have corrected.



Correct, I know full well one should never hire an engineer to perform a technicians job.

I have seen the fall out from this, many times.



I do expect this.

This is why I was so dumbfounded, by the gross errors being made.



Thanks, but I am not really offended, by those who attempt to make offending posts when I try to correct them.

I detest there offensive post.

I think it detracts from the value of the forum.

But if it's allowed, what should I do, discontinue correcting misinformation?

If everyone did that, this forum would have no useful information at all, or at least no one with lesser understanding to gain better understanding.

The evidence is right here, that you swallowed a hole can of worms of misinformation hook, line, and sinker, because you trusted that information posted by others, would be true, and it sounded plausible to you, when it really wasn't correct, but you mistrusted my corrections because you incorrectly assumed the matter must be more complex, such that one who is not an engineer, could not possibly be correct in their continued attempts to reduce the misinformation proliferation.

Do you really think, somebody reads all this copy & paste text from the posts before again and again in a single post? What's the point?

[s/v Jedi]

Originally Posted by CatNewBee

Do you really think, somebody reads all this copy & paste text from the posts before again and again in a single post? What's the point?

Exactly... or even believe a word of it

The only reason we need to keep posting is to protect the sailors who still think they can come to forums like this for good advice... it doesn't matter how wrong something is; it's still allowed to be posted so we need to continue calling it BS or else people like Ramblin' may convince people that they are actually posting all correct info. It's not the 90% correct info that they post (used to make it convincing) we need to worry about; it's the 10% that is wrong and may get people into trouble.

And it's not just that 48V would be good for super yachts or electric drive yachts only. Even for boats that build LFP house banks with 180Ah cells, they would be way better off with 16 cells in series than with a 4x4 serial-parallel setup. Even if they run a separate 24V bank for starting/winch/windlass.

[ramblinrod]

Originally Posted by s/v Jedi

Even for boats that build LFP house banks with 180Ah cells, they would be way better off with 16 cells in series than with a 4x4 serial-parallel setup. Even if they run a separate 24V bank for starting/winch/windlass.

Now here is a general statement I do not believe can be accepted at face value.

Implying "Barring any Mitigating Factors" doesn't help make this one valid.

It simply isn't true in many cases, perhaps even the majority of cases.

[evm1024]

Originally Posted by s/v Jedi

Exactly... or even believe a word of it

The only reason we need to keep posting is to protect the sailors who still think they can come to forums like this for good advice... it doesn't matter how wrong something is; it's still allowed to be posted so we need to continue calling it BS or else people like Ramblin' may convince people that they are actually posting all correct info. It's not the 90% correct info that they post (used to make it convincing) we need to worry about; it's the 10% that is wrong and may get people into trouble.

SNIP

Let me double that Exactly! And 10% coupled to hubris is not a good combination.

Does some of this remind you of ELIZA? It does me.

N.B. I could claim to be a High School dropout but my business card says Research Systems Engineer.

[ramblinrod]

Originally Posted by CatNewBee

Do you really think, somebody reads all this copy & paste text from the posts before again and again in a single post? What's the point?

I actually wish this were a copy and paste, but it is actually an individually typed response, as are all of my responses.

The reason they may look so familiar is because they are in response to the same invalid statements.

I don't know if anyone reads it.

I guess if one reads the invalid statement it is in response to, they may.

Somebody is obviously reading something, as they keep posting erroneous assertions, directly to me.

[evm1024]

Originally Posted by RR

Now here is a general statement I do not believe can be accepted at face value.

Implying "Barring any Mitigating Factors" doesn't help make this one valid.

It simply isn't true in many cases, perhaps even the majority of cases.

The player pushes his pawn forward hoping someone will take the bait.

[ramblinrod]

Originally Posted by evm1024

Let me double that Exactly! And 10% coupled to hubris is not a good combination.

Does some of this remind you of ELIZA? It does me.

N.B. I could claim to be a High School dropout but my business card says Research Systems Engineer.

So in other words, you do not have a bachelors or masters degree in engineering, by any accredited university?

Isn't this required to refer to one's self, and provide service, as an "engineer"?

What kind of marine service did you say you provide?

[transmitterdan]

There is no 100% right or wrong answer to the original question. But on balance a 48V system as described by s/v Jedi is nearly optimal in terms of several key parameters such as efficiency, cost, reliability and safety. It ticks all the boxes.

The only reason 12V remains popular is historical. If we had no legacy DC power equipment and we were starting from first principles then we would likely end up at 36 or 42VDC. We would not have massive parallel battery banks like we do now which are an obvious and documented fire hazard. We have seen several instances of 12V batteries in parallel where one explodes due to the high fault current. That does not usually happen with series banks.

There are numerous other benefits to a sub 50V distribution bus. I know of no commercially available high power (multi-kilowatt) DC system that uses 12V. Again, recreational cruising boats only use it for legacy reasons having nothing whatever to do with purported safety benefits. To cling to safety as a reason for staying with 12V is beyond absurd. It’s worse than that. We have 12V because “we’ve always done it that way” and that’s the only reason. That’s not a bad reason but that is the real reason.

[evm1024]

Originally Posted by ramblinrod

So in other words, you do not have a bachelors or masters degree in engineering, by any accredited university?

Isn't this required to refer to one's self, and provide service, as an "engineer"?

What kind of marine service did you say you provide?

Ha, ha,ha. How clever. Now we are into direct personal attacks. OK....

Let's see, you do not respect degrees so I'll keep with the high school dropout claim. Ya, ya ya, that my story and I'm not going to change it. Marine service, um, I sell anchors and do a little electrical work. That's the ticket.

Ya, ya. Before that I did a little work on research vessels for about 15 years. Just a bit of electrical/electronic work on vessels ranging from kayaks to 165' ships.

But I am thinking about retiring from the University where I work and getting an ABYC electrical certification. No, really - I'm not pulling your leg.

We are going to retire and finely get out long term cruising. I figure that I'm more likely to pick up some paying work from other cruisers If I have an ABYC Cert.

So how long did it take you to get your ABYC Marine Electrical certification?

[nebster]

The bloviation in this thread is absurd. How can any "professional" find so much time to reach the same nonsensical conclusions over and over?

As a full time 53VDC system user, it's perfectly possible to build up a safe design, even as an amateur. The benefits dramatically outweigh any downsides, most of which are fairly theoretical in the first place.