Comparative Safety: 12v v 24v v 48

[evm1024]

For the most part this appears to be a reasonable and noteworthy post. I have included a few comments.

Originally Posted by ramblinrod

OK, so we have gone round and round with lots of good info, and unfortunately, numerous posts that were riddled with errors, or were disrespectful and an attempt to shun consideration of alternate perspectives.

All I can say is, to each their own.

A good start in the beginning and end but I think that the part I bolded at least for me appears to miss the point that Weavis was making in his warning. I myself will attempt to refrain from making any such statements.

Are we likely to see an increasing number of recreational cruising boats with 48 Vdc systems in the future?

I think so.

I completely agree and I think that this is a good assessment.

Should we all jump on the bandwagon and start converting our boats from 12 Vdc to 48 Vdc, because someone, maybe even a small group of motivated boaters on the internet say it is cool and "The Way of the Future".

Depends. Probably not in most cases.

An interesting prospective. If we go back to the origin of this thread we see that there was no push to jump on the bandwagon and start converting
or any cool factor. At least I do not remember any and thus I cannot agree with the premise of your statement. It does not appear to be true. Of course that is just me and I may have missed something.

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.

Originally Posted by RR

When considering an original design or modification, one needs to consider the advantages and disadvantages of the options available to them.

So here are some pros and cons between 12 Vdc and 48 Vdc.

12 Vdc Electrical System

Pros:

1. Existing - Many or most boats already have it.
2. Product Base - More to choose from.
3. Cost - Many products are less expensive.
4. Electrocution - No risk (virtually).
5. Electrical Shock - Low risk
6. Fire - Lower risk due to "short circuit".
7. Arcing - Less prone to damage and overheat contact surfaces.
8. Familiarity - Long established standard.
9. Availability - Excellent everywhere.
10. Necessity - Very high (hard to operate with no 12 Vdc system).

Cons:

1. Load Limit: Lower, no "standard" but 3kW for 1 hour, 6 kW for 5 minutes is fine.
2. Heavier Cables: Increased copper cost.
3. Coolness: May be perceived as boring.
4. Generation Efficiency: May be lower.

48 Vdc Electrical System

Pros:

1. Coolness: Maybe perceived as exciting.
2. Load Limit: Higher - I use 12 kW for 1 hour, 24 kW for 5 minutes.
3. Generation Efficiency: May be higher.
4. Lighter Cables: May reduce cost.

Cons:
1. Existing: Rare, may require complete rewire and product replacement
2. Product Base - Less to choose from.
3. Cost - Many products are more expensive.
4. Electrocution - Higher risk (still low).
5. Electrical Shock - Higher risk.
6. Fire: Higher risk due to "short circuit".
7. Arcing: More prone to damage and overheat contrat surfaces.
8. Familiarity: Less.
9. Availability: Limited
10. Necessity: Some/many boats don't "require" > 12 Vdc system.

So to evaluate the real benefits (if any) of modifying an existing system, or designing a new system, around 48 Vdc vs 12 Vdc, one needs to weigh the pros and cons.

This is the kind of list I like to see. We can argue the merits of each item on the list and what should also be there etc. It forms a great basis for discussion.

Sometimes people get excited focusing on the pros and ignore the cons.

After living with the decision, they may regret the choice.

Some people will "actively promote" their choice, in attempt to gain "support" for, and hence feel better, about their decision.

Some will enjoy the benefits realized which outweigh the cons.

The above appears to me with the exception of the last line to be prejudicial. It appears to slander the majority of people who are interested in having a 48 volts system on their boats.

But, if it is an attempt to say that sometimes things work out and sometimes not then I will not quibble.

So lets look at the pros vs real benefits of choosing 48 Vdc.

1. Is it really cooler? Some may think so. Others may think, meh, 48 Vdc has been around along as 12 Vdc, just not traditionally on boats (hence lack of product availability and higher cost). Others may be afraid of it. While the higher risk of electrocution, electrical shock, and fire may be low to extremely low, the consequence is so high, that alone kills the idea.

2. Is a higher load limit necessary? If so, it may be warranted on this basis, if the advantage of supporting higher loads weighs out the cons. Do you really want to boil a pot of potatoes in the cabin (heat and humidity) vs BBQ out on the back deck? Do you really need AC, let alone running off batteries, that then you then need the high capacity chargers and batteries to support? Be sure to separate wants vs needs, and determine if they are even worth it.

3. Is generation efficiency really higher or better? In some cases it may be. Be sure to see what this really means to you. In other words, check that every pro "feature" is actually a benefit. If you have ample solar to recharge fully on a partially sunny day, higher charge efficiency may not really mean that much. A more efficient alternator may mean shorter run times, but if you typically only charge by alternator when changing anchorages, this may be no real benefit to you. If you charge by ICE generator EEE, it may only mean the difference of running 1.5 hours instead of 1.3 hours, and burning 75 cents less fuel per ICE generator charge cycle, and 15% less carbon emission, but 15% of almost nothing (in the grand scheme), is even less.

4. Lighter cables. This may save some copper. In a 8 HP thruster installation it may save about $40. In a total boat rewire, it may be $100's, but in comparison to the project cost, this may be infinitesimal. It is very possible for the higher 48 Vdc product costs, to vastly exceed the cable savings, so this may be no real benefit at all.

5. Danger. Just as everyone has different boat models preferences, everyone has different risk tolerance. It is wise to consider likelihood of hazard, vs consequence of hazard. Even if a risk of electrocution is extremely small, the consequence (death) is pretty severe. The higher risk of shock is actually quite possible, and the consequence may range from nuisance to some form of injury. The higher risk of fire is real. By it's very nature, 48 Vdc has a higher potential to start a fire is a short circuit situation. The consequence is very severe.

As we have seen the above opinions are subject to debate and perhaps would be best taken up in later posts.

Clearly you have a right to express your opinion.

EVERYONE'S PREFERENCES AND BIASES WILL BE DIFFERENT!

Outstanding statement!

This is why for this, or any significant cost (time and/or money) project, we recommend a thorough vessel design and configuration review, boater needs and wants assessment, with cost/benefit analysis.

Opinions and weighting of pros and cons will differ likely as much as there are numbers of different models of boats.

Another outstanding statement. I would add to it ...as there are numbers of different models of boats and needs and desires of boat owners.

Many boat owners are very down to earth and go for plain old tried and true solutions for their boats. Others are really motivated by the WOW factor and enjoy exciting new things on the bleeding edge.

I certainly cannot say that either position is the Correct one or more valid than the other. For an owner that thought things through and said I want WOW, who am I to say one way or another?

I believe it is better for boaters to make informed decisions based on their actual boat and personal needs, rather than just jump on the bandwagon of internet "fans" that have nothing to lose if the outcome is high cost with little or no actual benefit realized.

At first reading this paragraph makes good sense but the problem is not with what it says but with what it leaves out. For example the statement ...actual boat and personal needs would be better if it read ...actual boat and personal needs and desires.

That is one example of the problem I have with the paragraph.

I currently work for a research group at a university/med school/hospital. We have juvenile test subjects and as you might suspect kids pick up on everything. We go to great lengths to avoid projection of any implicit bias into our tests.

Simply stated we try to weed out our researchers implicit bias in their interactions with our test subjects.

We would never say (to make the point) Would you rather have this nasty, cavity causing yucky chocked full of sugar candy bar or this wonderful healthful GMO free all natural salt free popcorn?

In my opinion that paragraph is full of implicit bias.

Which is all the more reason why every boater really needs to evaluate "What is best for me", which will naturally be different than for someone else.

I think that implicit bias crept in again. What is best for me has a lot of unstated parameters. I myself (but then again that is just me) would phrase it as - "What I want and how to achieve it if possible". Clearly someone who can afford a superyacht has a much different opinion of what is best for them as compared to someone with a $30k/year income with a $100k student loan and a baby onthe way.

Anyway, I hope this summary / review helps.

It most certainly does help. And if nothing else it shows (though my responses) that there is room for differences of opinion. I am sure that we all agree that none of us have the same exact opinion and that there is room for differing opinions. Sometimes we have to agree to disagree.

And to follow up on that last thought (agree to disagree) I think that if were to find myself stating my opinion over and over again then I most likely would be trying to force my opinion on other people with differing opinions. I pledge to not force my opinion on others.


And lastly I'll try to keep any of my future posts to a single topic where ever possible.

[ramblinrod]

Originally Posted by Q Xopa

Terrific Post!

Most of us here know you have a lot to offer.

Informed opinions (even if they are different to others is fine).

I am here to learn, consider new ideas and contribute if I think I can.

This is what I believe is what CF is and should be about.

I think most of us arent really so keen to hear "wrong, correct, strawman etc" in reference posts or to anyone, particularly other repected contributors of which there are many on here.

Thanks.

Thanks for your kind words.

Regarding the bantering, I completely agree.

Until this behaviour is prohibited, some will be less willing to contribute useful information for fear of this senseless retaliation, and it will reduce the accessibility to valid information, posted by those who power though it.

It is a form of cyber bullying.

This is why I object so vehemently to intentionally misleading posts, that misrepresent the positions of others. (AKA strawman arguments.)

[ramblinrod]

Originally Posted by evm1024

For the most part this appears to be a reasonable and noteworthy post. I have included a few comments.

Comments reviewed.

Seems to be little or no change, other than alternative wording with the same meaning.

So the original post, without any edits, stands on its own merit.

Agreed?

[evm1024]

Originally Posted by ramblinrod

Comments reviewed.

Seems to be little or no change, other than alternative wording with the same meaning.

So the original post, without any edits, stands on its own merit.

Agreed?

Rod, I cannot agree more that everyone's post stand on their own merits. That goes without saying.

And thank you for taking the time to review my comments. It was courteous of you considering the time and thought that I put into those comments.

I am surprised that you found them to be of little meaning. I think that they are quite significant especially in regards to implicit bias but I guess we will have to agree to disagree.

I would urge you to revisit my comments and view them in the light of how we could improve our posts in the future rather than a critique of your post.

[s/v Jedi]

Originally Posted by ramblinrod

So here are some pros and cons between 12 Vdc and 48 Vdc.

12 Vdc Electrical System

Pros:

1. Existing - Many or most boats already have it.
2. Product Base - More to choose from.
3. Cost - Many products are less expensive.
4. Electrocution - No risk (virtually).
5. Electrical Shock - Low risk
6. Fire - Lower risk due to "short circuit".
7. Arcing - Less prone to damage and overheat contact surfaces.
8. Familiarity - Long established standard.
9. Availability - Excellent everywhere.
10. Necessity - Very high (hard to operate with no 12 Vdc system).

1. Existing... is that a pro? 12V is better because it exists? I would delete this point.

2. Product Base... all the wiring, breakers, terminals, terminal blocks etc. are the same so availability is the same. In case of motors for starters, winches, windlass etc. then there are more offerings for 12V than there are for 48V. But for boats who need more than a car-grade 12V system, all the motors they require are available in 24V so that makes 12V less desirable than 24V.

3. Cost... in case of motors etc. 12V may be cheaper yes.

4. electrocution: delete, irrelevant for anything below 50V

5. electrical shock: delete, irrelevant for anything below 50V

6. fire: more risk for 12V so this is a con for 12V and a pro for 24/48V. Reason is simply that with 12V we have a current that is 4 times higher so in any hotspot due to corrosion etc. we get 16x as much heat development ( I^2 = 4^2 = 16 )

7. arcing: more arcing for 12V because current is higher and arcing occurs when disconnecting a load. The big error here is that for high voltage arcing we mean that an arc forms through insulation or just through plasma in an otherwise static environment. We talking many kV here so all that is irrelevant for anything below 50V. The arcing described by me and other EE's is contact-arcing inside a switch, breaker, solenoid etc. when a large current is disconnected. Here it is current, not voltage, that is damaging.

8. Familiarity: irrelevant because everything is the same. No additional knowledge required.

9. Availability: yes, 12V pumps etc. are easier to find than 24V let alone 48V

10. Necessity: compared with 48V correct. Compared with 24V (which was part of it) incorrect. Every winch, windless, starter etc. is available for 24V.

so that leaves point 3... if at all?

These posts are nonsense because it isn't about 12V vs 48V... it is about powering an induction cooker with an inverter, or requiring a high hp bow thruster and other high loads that -demand- better than a 12V house bank while smaller boats that cook on propane are just fine on 12V

[evm1024]

Originally Posted by s/v Jedi

SNIP

7. arcing: more arcing for 12V because current is higher and arcing occurs when disconnecting a load. The big error here is that for high voltage arcing we mean that an arc forms through insulation or just through plasma in an otherwise static environment. We talking many kV here so all that is irrelevant for anything below 50V. The arcing described by me and other EE's is contact-arcing inside a switch, breaker, solenoid etc. when a large current is disconnected. Here it is current, not voltage, that is damaging.

SNIP

Great post - Point 7 is a fantastic point to examine.

As we know

An electric arc is the form of electric discharge with the highest current density. The maximum current through an arc is limited only by the external circuit, not by the arc itself.

This is caused by the inverse relationship between the current of the arc and the arc's resistance.

More current, lower resistance, more current, lower resistance until the current is limited by the external circuit.

A 12 volt system with its larger cables and higher amperage for the same KWh can supply a larger current than a 24 volt or 48 volt system.

ALL (with few if any exceptions) circuit breakers and switches of the quality that we use on our boats are made with internal anti-arcing components.

[transmitterdan]

All contactors and breakers will need to be designed and certified for 48V. I think it’s easy to find breakers and contactors with contacts that handle up to 65V but it needs to be checked.

Fuses are the main worry. Some fuses found in 12V systems are not certified for 48V.

Arcing of contacts is mostly a function of current and the inductance of the source and load. Arcing is about the same between 12V and 48V contactors and breakers. That’s because the inductance/current ratio is about constant for a given power load. Higher power motors have higher tendency to cause contact arcing. At 48V it is easy and cheap to suppress these arcs. Much cheaper than for 12V.

I find no compelling reason to stay with 12V except for legacy reasons. For a new build I would not go below 24V and would probably go for 36V since my power needs would be about 4kW. But 4kW is too much for a 12V system.

[evm1024]

Good points RE Arcing and Fuses.

I took a look at some common fuses, ANL and Class-T for example. I found that they were both rated above 48 volts (I knew the Class-T were but not the ANL).

From some of Mainesail's postings I'm not sure that I would use ANL for a 48 volt application.

What was significant was the voltage rating of the fuse holders. All of the ones I looked at from Ancor were rated at 36 volts or less.

The same was true for small fuses. You can get the typical 3GA glass fuse footprint (which is not 48 volt rated) in a ceramic body style that is rated for 60 VDC or more.

But again the problem is finding fuse holders that are rated above 36 VDC.

[s/v Jedi]

Originally Posted by evm1024

Good points RE Arcing and Fuses.

I took a look at some common fuses, ANL and Class-T for example. I found that they were both rated above 48 volts (I knew the Class-T were but not the ANL).

From some of Mainesail's postings I'm not sure that I would use ANL for a 48 volt application.

What was significant was the voltage rating of the fuse holders. All of the ones I looked at from Ancor were rated at 36 volts or less.

The same was true for small fuses. You can get the typical 3GA glass fuse footprint (which is not 48 volt rated) in a ceramic body style that is rated for 60 VDC or more.

But again the problem is finding fuse holders that are rated above 36 VDC.

Class T fuses and holders are rated for 160V DC. These are used for 144V DC installations.

For breaker panels you simply select C-series breakers instead of A-series. They are 80V DC rated: https://www.bluesea.com/products/735...le_Pole_15_Amp

[Q Xopa]

Originally Posted by ramblinrod

Thanks for your kind words.

Regarding the bantering, I completely agree.

Until this behaviour is prohibited, some will be less willing to contribute useful information for fear of this senseless retaliation, and it will reduce the accessibility to valid information, posted by those who power though it.

It is a form of cyber bullying.

This is why I object so vehemently to intentionally misleading posts, that misrepresent the positions of others. (AKA strawman arguments.)

This is definite progress. Agree on most of your reply, until the last two paras.

However, if I might request please-

objecting vehemently, is fine providing it does not include-

Telling people they are wrong by stating 'Incorrect' or you are right by stating you are 'Correct'. Let's try and be a bit more humble. I certainly dont know everything and I very much doubt any of us do.

Non of us can categorically state pretty much anything to be known as a fact (except maybe death and taxes). Only that we believe it.

Or that they are a Strawman, by stating 'Strawman alert'. This is a personal attack and is frankly disrespectful and indeed as you say a form of cyber bullying.

So if we could proceed without some of these words, I think things can move along much nicer. We can all discuss and learn from each other.

Please feel free to state your view and what you believe.

[Q Xopa]

Originally Posted by s/v Jedi

1. Existing... is that a pro? 12V is better because it exists? I would delete this point.

2. Product Base... all the wiring, breakers, terminals, terminal blocks etc. are the same so availability is the same. In case of motors for starters, winches, windlass etc. then there are more offerings for 12V than there are for 48V. But for boats who need more than a car-grade 12V system, all the motors they require are available in 24V so that makes 12V less desirable than 24V.

3. Cost... in case of motors etc. 12V may be cheaper yes.

4. electrocution: delete, irrelevant for anything below 50V

5. electrical shock: delete, irrelevant for anything below 50V

6. fire: more risk for 12V so this is a con for 12V and a pro for 24/48V. Reason is simply that with 12V we have a current that is 4 times higher so in any hotspot due to corrosion etc. we get 16x as much heat development ( I^2 = 4^2 = 16 )

7. arcing: more arcing for 12V because current is higher and arcing occurs when disconnecting a load. The big error here is that for high voltage arcing we mean that an arc forms through insulation or just through plasma in an otherwise static environment. We talking many kV here so all that is irrelevant for anything below 50V. The arcing described by me and other EE's is contact-arcing inside a switch, breaker, solenoid etc. when a large current is disconnected. Here it is current, not voltage, that is damaging.

8. Familiarity: irrelevant because everything is the same. No additional knowledge required.

9. Availability: yes, 12V pumps etc. are easier to find than 24V let alone 48V

10. Necessity: compared with 48V correct. Compared with 24V (which was part of it) incorrect. Every winch, windless, starter etc. is available for 24V.

so that leaves point 3... if at all?

These posts are nonsense because it isn't about 12V vs 48V... it is about powering an induction cooker with an inverter, or requiring a high hp bow thruster and other high loads that -demand- better than a 12V house bank while smaller boats that cook on propane are just fine on 12V

Sorry for the slight thread drift, but any clues where I can get 24v starters from for my 4JH4-TE?

[s/v Jedi]

Originally Posted by Q Xopa

Sorry for the slight thread drift, but any clues where I can get 24v starters from for my 4JH4-TE?

I would have someone rewind it for 24V or just use the current 12V starter on 24V.

[Q Xopa]

Originally Posted by s/v Jedi

I would have someone rewind it for 24V or just use the current 12V starter on 24V.

Yeh thanks. Ive heard and am considering just using the 12v starter on 24v. I have heard they spin quicker and chew out teeth quicker.

I have also asked a few places about rewinding. I havent found one that does them yet. They dont seem to be as common as I remember them being.

Thanks anyhow.

[s/v Jedi]

Originally Posted by Q Xopa

Yeh thanks. Ive heard and am considering just using the 12v starter on 24v. I have heard they spin quicker and chew out teeth quicker.

I have also asked a few places about rewinding. I havent found one that does them yet. They dont seem to be as common as I remember them being.

Thanks anyhow.

You normally find them when Googling for "starter alternator generator repair shop"

[Q Xopa]

Originally Posted by s/v Jedi

You normally find them when Googling for "starter alternator generator repair shop"

Thanks.