48V as main DC voltage on boat - anyone?

[geoffa]

I neglected to mention I do not have a generator nor shore power for the 48v cct. I rely on 12 200w solar panels. The smart MPPT works more efficiently the closer the output voltage is to the input voltage.

[Clipperau]

Will try using 60v instead of 80 and see what happens. Thanks

[mdenize]

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.

Whew I just ploughed through all the posts hoping ranchero76 had a few answers that came close to the original question, With the exception of a very few it seems not, so I feel compelled to at least answer in the spirit of someone who is doing it. I know this is an old post that has been hijacked but maybe the OP is still watching and hoping

I am an electronics technician with an 8000 hour navy apprenticeship and lots of time in classrooms to get a few letters behind my name but all that is irrelevant to the question.

Yes, I am as close to doing it as anyone. We live on a remote island with no Grid, we generate all our own Electricity (mainly 3.5kW of Solar and 750w of hydro) we store this energy in 50kWhrs of Lead acid batteries at >/=50vDC (48v nominal) and convert it to 230v AC for all modern household uses(Electric oven, dishwasher, toaster, microwave, walk in chiller, MIG TiG,Arc welding etc etc (that answers why WE use 48vDC!). Our house is 40m from high tide in one of the windiest places around (45 knots today)so plenty of salt all around. I have done this for 18 years on the same LA batteries so have a bit of experience with keeping them happy. Everything is off the shelf and nothing is a one off wonder.

How is this relevant? Well I am very confident with 48vDC as a standard and as we have so much renewable energy spare I have a project. It is an 8.5m sailing cat which has 40kWhrs of LIFe at >/=52v (48v nominal.) The main difference is the 48vDC will be limited to the main engines (yet to be installed) and inverter (both again a standard) directly with everything else that does not need such high currents run at 12v (yay for LEDs).

So there you go Ranchero76 it can be done, dont let the flat earthers tell you it can not (unless they have done it).

I would be very happy to share my experience with you

Best Wishes

Mark

[foggysail]

GOOD post Mark. My feeling is that if people are so concerned about 48V then maybe they should not use 120VAC on their boats.

There are reasons though to stay with the old 12V systems such as available 48V instrumentation....VHF’s and so forth

[ramblinrod]

Originally Posted by foggysail

GOOD post Mark. My feeling is that if people are so concerned about 48V then maybe they should not use 120VAC on their boats.

There are reasons though to stay with the old 12V systems such as available 48V instrumentation....VHF’s and so forth

I think the point with any electrical system design, is to make it safe, functional, and easily serviceable.

As previously posted, a 48 Vdc (or higher) system on a boat can make sense, especially in the case of a large boat with high loads, and especially in the case of electric propulsion.

In doing so, it is important to mitigate the risk of the higher voltage, including insulation and isolation.

FWIW, responding to the backhanded comment regarding 120 Vac, as mentioned previously, the marine electrical standards that apply to 120 Vac, provide numerous safety measures to mitigate the risk of the higher voltage. Perhaps those who don’t realize this shouldn’t be telling others how they should wire boats.

[foggysail]

No one has suggested boats should be designed and built with inadequate safety. And no handyman should deviate or change a properly designed and wired system on a boat or any other place.

[geoffa]

I surmise there is a bunch of "heated agreement on this thread". If we all came down from Mars tomorrow I know it would be 48v. Trouble is we are all victims to a mature market of 12vdc, would we be doing a bottom up design, integrating LiFePo4, solar and optimising the opportunity 48v dc is a no brainer. Yes I have lots of 12v. To me the 48v was driven by two key decisions, and I squared R losses and not in the cables. Three key components worked out better at 48v dc, isolation cct breakers, the MPPT for solar and the inverters. The latter two being the most heat sensitive and the one running nearly full time. The 16 times reduced internal current should reduce loads on the most sensitive internal components apart from more broadly managing the external heat load. By going 48v there was a price difference and allowed me to use miniature cut breakers because of the total reduced current. I actually don't have a 48v rail as such as cable runs from the LiFePo4, inverter, cct breakers and MPPT are but a few inches.
On the question of safety a sensible risk analysis of 48v would probably give you a safer system as the 48v for any given capacity will have a lesser short cct impedance and hence the likelihood of a welded connection.
I might add I was never able to obtain a short cct impedance for my LiFePo4 pack and most off the shelf fuses seem to be rated at 12v. This is part of the reason there is no 48v distribution as such.
I could not find any public domain data on 48v fibrillation risk.
I recollect designing a welder many moons ago as an electrical engineering student and the safety test was a welder with a wet shirt leaning against steel structure whilst changing an electrode. I recollect the voltage was 72v.
Would I be able to go full 48v dc, for dc cirvuits absolutely, unfortunately the market does not allow.
Geoff
FIEAust, CPEng, MCEE, NER
PS what powers up a rail gun, super capacitors, lifepo4, and big generators. Now there is some interrupting capacity!!

[ranchero76]

Thanks to all, especially to these who are doing or planning to do it. For me - some things changed in life (financial matter), so unfortunately sailing adventure has to wait...
For these who smart enough to try new things - there are tons of options for you on the market today.
For these who worry about small 12v appliances - 48v to 12v convertor 120W, 90% efficiency is $3.99 on eBay with free shipping! And don't start "it's probably not very reliable" - item has great feedback and it literally can be consumable - buy 20 of them, put in plastic bags and never worry that it might break down.
Same with 48v to 120V or to 240V convertors - they cheap as dirt, you can have bunch of them for spares if reliability really concerns you.

So the only things which would be concern - heavy 12v loads like winches etc.
I would spend effort and replace all motors with 48v motors, using as fewer models 48v brushless motors as possible (fewer spares needed). They are much smaller, have no brushes and can be easily found in IP67 housing (waterproof) if needed.
Than just buy few extra and keep spares - problem solved. Even though in most countries motors can be rebuilt, prices on modern 1-2kW brushless motors so affordable that easier to carry spares in my opinion.

[mdenize]

Originally Posted by geoffa

I surmise there is a bunch of "heated agreement on this thread". If we all came down from Mars tomorrow I know it would be 48v. Trouble is we are all victims to a mature market of 12vdc, would we be doing a bottom up design, integrating LiFePo4, solar and optimising the opportunity 48v dc is a no brainer. Yes I have lots of 12v. To me the 48v was driven by two key decisions, and I squared R losses and not in the cables. Three key components worked out better at 48v dc, isolation cct breakers, the MPPT for solar and the inverters. The latter two being the most heat sensitive and the one running nearly full time. The 16 times reduced internal current should reduce loads on the most sensitive internal components apart from more broadly managing the external heat load. By going 48v there was a price difference and allowed me to use miniature cut breakers because of the total reduced current. I actually don't have a 48v rail as such as cable runs from the LiFePo4, inverter, cct breakers and MPPT are but a few inches.
On the question of safety a sensible risk analysis of 48v would probably give you a safer system as the 48v for any given capacity will have a lesser short cct impedance and hence the likelihood of a welded connection.
I might add I was never able to obtain a short cct impedance for my LiFePo4 pack and most off the shelf fuses seem to be rated at 12v. This is part of the reason there is no 48v distribution as such.
I could not find any public domain data on 48v fibrillation risk.
I recollect designing a welder many moons ago as an electrical engineering student and the safety test was a welder with a wet shirt leaning against steel structure whilst changing an electrode. I recollect the voltage was 72v.
Would I be able to go full 48v dc, for dc cirvuits absolutely, unfortunately the market does not allow.
Geoff
FIEAust, CPEng, MCEE, NER
PS what powers up a rail gun, super capacitors, lifepo4, and big generators. Now there is some interrupting capacity!!

Spot on! There is one point to add 48v has been a standard since the ark. It is most widely used as the standard ringing voltage of analog telephones (does anyone remember those days?) so all telco grade analog PABX,s and exchanges ran 48v through out. This means that there are a alot of power supplies, relays, breakers, fuses and lamps designed for it. Why did they use it through all that inground copper? all of those reasons above but most of all it was SAFE. you can lick your fingers and touch the busbars attached to my 1000AH battery and barely feel it let alone die. The most I have ever felt was when I cut myself and was finger tightening some nuts on the busbar (wet, salty tight contact) but even that was a tingle. Drop the phone in the bath when it is ringing and you are in it and you will not die (of electrocution anyway)

[ranchero76]

Originally Posted by mdenize

The most I have ever felt was when I cut myself and was finger tightening some nuts on the busbar (wet, salty tight contact) but even that was a tingle.

Now that would be called hands on personal experience

[ramblinrod]

Originally Posted by geoffa

I surmise there is a bunch of "heated agreement on this thread". If we all came down from Mars tomorrow I know it would be 48v. Trouble is we are all victims to a mature market of 12vdc, would we be doing a bottom up design, integrating LiFePo4, solar and optimising the opportunity 48v dc is a no brainer. Yes I have lots of 12v. To me the 48v was driven by two key decisions, and I squared R losses and not in the cables. Three key components worked out better at 48v dc, isolation cct breakers, the MPPT for solar and the inverters. The latter two being the most heat sensitive and the one running nearly full time. The 16 times reduced internal current should reduce loads on the most sensitive internal components apart from more broadly managing the external heat load. By going 48v there was a price difference and allowed me to use miniature cut breakers because of the total reduced current. I actually don't have a 48v rail as such as cable runs from the LiFePo4, inverter, cct breakers and MPPT are but a few inches.
On the question of safety a sensible risk analysis of 48v would probably give you a safer system as the 48v for any given capacity will have a lesser short cct impedance and hence the likelihood of a welded connection.
I might add I was never able to obtain a short cct impedance for my LiFePo4 pack and most off the shelf fuses seem to be rated at 12v. This is part of the reason there is no 48v distribution as such.
I could not find any public domain data on 48v fibrillation risk.
I recollect designing a welder many moons ago as an electrical engineering student and the safety test was a welder with a wet shirt leaning against steel structure whilst changing an electrode. I recollect the voltage was 72v.
Would I be able to go full 48v dc, for dc cirvuits absolutely, unfortunately the market does not allow.
Geoff
FIEAust, CPEng, MCEE, NER
PS what powers up a rail gun, super capacitors, lifepo4, and big generators. Now there is some interrupting capacity!!

Well, the OP and some other posters have done their best to provoke retaliatory responses.

Example, "Is any one brave enough too..."

Choosing a marine electrical system voltage is not a matter of braveness or cowardess, it is simply a matter of considering all aspects of the available options. Everyone is free to choose as they wish, even if their plans are very ill-conceived in the opinions of others.

Every time I hear someone use the term "no brainer" I chuckle to myself.

In my opinion, there is absolutely no aspect of marine electrical system design and installation that does not warrant considerable thought and proper weighting of advantages and disadvantages of various scenarios.

I am on earth, and have been here all my life.

I am an electronic engineering technician, with 40 years experience.

I own and operate a marine service business where I consult, design, install, and service marine electrical systems.

I have many published articles on marine electrical systems.

I develop and conduct marine electrical system seminars for boating groups.

In my opinion, going to 48 Vdc without thought (using ones brain), would be a huge mistake and a poor choice in most cases.

Again, for vessels with very high loads, (esp. electric propulsion) 48 Vdc or even higher may be warranted after weighing risk vs reward.

In my opinion, and based on many evaluations, for most ICE powered cruising boats to 40 ft, 12 Vdc will suffice and be the best all around choice.

Between 40 ft and 60ft, 24 Vdc for the higher loads will usually be perfect.

Beyond that, the heavy load equipment is often better served powered by a diesel generator and/or hydraulics.

(Note that I have placed definite lines based on length, which are simply a general guide based on my education, experience, and history of evaluating exactly this subject in real life for real boaters. There can certainly be cases where the lines are blurred a little.)

I recommend anyone with a 40ft or less ICE powered boat, considering a DC system greater than 12 V, or with a 40- 60 ft ICE powered boat, considering a DC system greater than 24 Vdc, to really think it through, or get some pro advice; yes it can be done, but just because it can be done doesn't mean it should be, for all of the reasons previously stated.

If someone's opinion differs, that's absolutely fine, but that differing opinion does not make mine or any alike, wrong, misguided, uneducated, inexperienced, cowardly, old-fashioned, non-current, other worldly, or any of the other ridiculous accusations, implications, assertions, or attempts to discredit, valid in any way.

[Cadence]

Originally Posted by ramblinrod

Well, the OP and some other posters have done their best to provoke retaliatory responses.

Example, "Is any one brave enough too..."

Choosing a marine electrical system voltage is not a matter of braveness or cowardess, it is simply a matter of considering all aspects of the available options. Everyone is free to choose as they wish, even if their plans are very ill-conceived in the opinions of others.

Every time I hear someone use the term "no brainer" I chuckle to myself.

In my opinion, there is absolutely no aspect of marine electrical system design and installation that does not warrant considerable thought and proper weighting of advantages and disadvantages of various scenarios.

I am on earth, and have been here all my life.

I am an electronic engineering technician, with 40 years experience.

I own and operate a marine service business where I consult, design, install, and service marine electrical systems.

I have many published articles on marine electrical systems.

I develop and conduct marine electrical system seminars for boating groups.

In my opinion, going to 48 Vdc without thought (using ones brain), would be a huge mistake and a poor choice in most cases.

Again, for vessels with very high loads, (esp. electric propulsion) 48 Vdc or even higher may be warranted after weighing risk vs reward.

In my opinion, and based on many evaluations, for most ICE powered cruising boats to 40 ft, 12 Vdc will suffice and be the best all around choice.

Between 40 ft and 60ft, 24 Vdc for the higher loads will usually be perfect.

Beyond that, the heavy load equipment is often better served powered by a diesel generator and/or hydraulics.

(Note that I have placed definite lines based on length, which are simply a general guide based on my education, experience, and history of evaluating exactly this subject in real life for real boaters. There can certainly be cases where the lines are blurred a little.)

I recommend anyone with a 40ft or less ICE powered boat, considering a DC system greater than 12 V, or with a 40- 60 ft ICE powered boat, considering a DC system greater than 24 Vdc, to really think it through, or get some pro advice; yes it can be done, but just because it can be done doesn't mean it should be, for all of the reasons previously stated.

If someone's opinion differs, that's absolutely fine, but that differing opinion does not make mine or any alike, wrong, misguided, uneducated, inexperienced, cowardly, old-fashioned, non-current, other worldly, or any of the other ridiculous accusations, implications, assertions, or attempts to discredit, valid in any way.

Lets all go back to the 32 volt system. circa mid 50s.