24volts for Narrowboats

[Yoda]

All large equipment was based on 24v awhile ago and indeed American cars also used this voltage. Other vehicles also use 48 volts but much less now. On long vessels it is sensible to operate at a higher voltage than 12v because of the voltage drop, lack of gear withstanding. It was the European motor industry that set 12v as a standard therefor there is lots of gear about which is cheap.

 

In future where battery back up power for traction will be the norm, it is more likely that cars will be 24 or 48 volts as a common standard.

[DHutch]

Dhutch (Daniel) - if you don't mind me asking, what manufacturer of inverter / charger have you got installed ?

Our charge is a three-head sterling marine 25amp unit, which is now 18 years old as it is origanal equipment.

 

The inverter is a small 300watt MSW unit, which was perchased from maplins (in all ways the same as the 12v 300w msw unit).

 

We're very happy with the operation of both of these units, although the would be benfit in having a large inverter with the ablity to run mains powertools we currently make use of a honda Ex1000 (also 18yo) for this task.

 

If i was builting a boat from scratch i would have to spend a while looking at what there was to offer, but if i had to buy somthing today, ive been very impressed with what ive seen of the victron phonix charger/inverter units.

[Arnot]

Gibbo, you are an argumentative old curmudgeon! Did you get out of the wrong side of the bed today? Go and get some happy pills down your neck... What makes you think you have a monoply on facts?

 

FWIW my boat is actually 12V but I often work on 24V installations.

 

There are a couple of things here that I would take issue with, not necessarily incorrect but more incomplete.

 

Whilst it is fair(ish) to say that 24 volt battery chargers, inverters etc, are not more efficient than the equivalent 12 volt model. I would dispute that they are within 0.5% I would guess that 5% would be nearer the mark but as you say, this should not come into the equation as a major determinanat for making a decision.

 

There is of course the question of the alternator, 24V ones at higher outputs are very definitely more efficient and if the OP as a liveaboard intends to use this form of charging a lot then over the lifetime of the boat, quite a bit of diesel could be saved.

 

I am quite sure that any manufacturer of predominantly 12V equipment finds producing a small quantity of 24V stuff a bit of an inconvenience but no-one forces them to do it. I rather think that if we let the convenience of manufacturers in carrying on making what they find easiest would not promote innovation. My Heart bleeds for them but I am quite content to be an "awkward b*st*rd" when necessary to get what I want.

 

For all this, for the OP, the 12V option is going to make life easier insofar as build and subsequent repairs go but the 24V option will probably save you money in the longer term.

 

Regards

 

Arnot

Edited August 31, 2009 by Arnot

[Albion]

How the two 'resident oafs' can start a slanging match over such an innocuous topic I don't know, (or are we down to one now).

 

Not quite sure how this comment adds to the debate other than being deliberately provocative. There was absolutely no need for this sentence in the posting.

Roger

[Yoda]

Gibbo, you are an argumentative old curmudgeon! Did you get out of the wrong side of the bed today? Go and get some happy pills down your neck... What makes you think you have a monoply on facts?

 

FWIW my boat is actually 12V but I often work on 24V installations.

 

There are a couple of things here that I would take issue with, not necessarily incorrect but more incomplete.

 

Whilst it is fair(ish) to say that 24 volt battery chargers, inverters etc, are not more efficient than the equivalent 12 volt model. I would dispute that they are within 0.5% I would guess that 5% would be nearer the mark but as you say, this should not come into the equation as a major determinanat for making a decision.

 

There is of course the question of the alternator, 24V ones at higher outputs are very definitely more efficient and if the OP as a liveaboard intends to use this form of charging a lot then over the lifetime of the boat, quite a bit of diesel could be saved.

 

I am quite sure that any manufacturer of predominantly 12V equipment finds producing a small quantity of 24V stuff a bit of an inconvenience but no-one forces them to do it. I rather think that if we let the convenience of manufacturers in carrying on making what they find easiest would not promote innovation. My Heart bleeds for them but I am quite content to be an "awkward b*st*rd" when necessary to get what I want.

 

For all this, for the OP, the 12V option is going to make life easier insofar as build and subsequent repairs go but the 24V option will probably save you money in the longer term.

 

Regards

 

Arnot

 

I don't understand that, as demand is the same and as you can only generate enough to satisfy the demand, would it not be the same?

[Gibbo]

Right we'll take your points one by one...............

 

Gibbo, you are an argumentative old curmudgeon!

 

No I'm not

 

Did you get out of the wrong side of the bed today? Go and get some happy pills down your neck... What makes you think you have a monoply on facts?

 

I don't. But I do recognise when someone has a monopoly on non-facts.

 

FWIW my boat is actually 12V but I often work on 24V installations.

 

Ditto

 

Whilst it is fair(ish) to say that 24 volt battery chargers, inverters etc, are not more efficient than the equivalent 12 volt model. I would dispute that they are within 0.5% I would guess that 5% would be nearer the mark but as you say, this should not come into the equation as a major determinanat for making a decision.

 

Well..... Rich Electric 12 volt 1500 watt pure sine at 85% rated power is 86.8% efficient. The same unit in 24 volt is 87.1% efficient. That, by my calculations is a difference of either 0.3% of the maximum possible or 0.35% in absloute terms. That is within 0.5%

 

If you reckon it is 5% better then that means the 24 volt unit would be 91.14% efficient which is completely wrong. And even it it was right, it's still a relatively insignificant amount.

 

There is of course the question of the alternator, 24V ones at higher outputs are very definitely more efficient

 

Yes they are. But again, not by much. We're still talking a few percent at most.

 

I am quite sure that any manufacturer of predominantly 12V equipment finds producing a small quantity of 24V stuff a bit of an inconvenience but no-one forces them to do it. I rather think that if we let the convenience of manufacturers in carrying on making what they find easiest would not promote innovation. My Heart bleeds for them but I am quite content to be an "awkward b*st*rd" when necessary to get what I want.

 

But you've missed the point. The point is that 12 volt equipment is more expensive because of the necessity to make 24 volt equipment or to make dual voltage equipment. All my products would actually retail at about 15% less if they weren't dual voltage.

 

Gibbo

 

Not quite sure how this comment adds to the debate other than being deliberately provocative. There was absolutely no need for this sentence in the posting.

Roger

 

I've kinda got used his rambling now. My grandmother did a similar thing in her last few years.

 

Gibbo

[Arnot]

I don't understand that, as demand is the same and as you can only generate enough to satisfy the demand, would it not be the same?

Once the current produced is passed through the batteries, it doesn't make any difference to the battery charging efficiency or speed of charge, it is the efficiency of the alternator in generating that power that is better at 24V.

 

Because for a given power output, the current is halved, the losses in the stator windings are reduced by 75% and the losses in the rectifier by a similar amount. As a consequence, less mechanical power input is required to generate a given electrical ouptut and hence less diesel is used. As a useful byproduct, the reduced losses tend to mean that 24V alternators run cooler and therefore tend to last longer.

 

Hope this helps,

 

Regards

 

Arnot

[Gibbo]

Because for a given power output, the current is halved, the losses in the stator windings are reduced by 75%

 

Well this isn't strictly true is it. The losses would be reduced by 75% IF the stator was the same (and could miraculously produce the same voltage). But it isn't the same. It is thinner wire and more windings. In fact it's wire about half the CSA, and about twice as many of them. So stator losses are reduced by about.... er........... nothing.

 

In the real world, they are actually slightly lower because they don't quite put twice as many winding of half the CSA wire in. But, again, we're talkiing a few percent. Not 75%!

 

And also consider that the stator losses are only about a 1/3 of the total losses. So reducing stator losses by 3% only results in an overall alternator loss reduction of 1%

 

and the losses in the rectifier by a similar amount.

 

Again, not quite. For an equal comparison you have to use rectifiers with double the voltage rating. So for the same package size they will have the same losses at half the current.

 

As a consequence, less mechanical power input is required to generate a given electrical ouptut and hence less diesel is used. As a useful byproduct, the reduced losses tend to mean that 24V alternators run cooler and therefore tend to last longer.

 

Again, a few percent.

 

Gibbo

[Timleech]

Well this isn't strictly true is it. The losses would be reduced by 75% IF the stator was the same (and could miraculously produce the same voltage). But it isn't the same. It is thinner wire and more windings. In fact it's wire about half the CSA, and about twice as many of them. So stator losses are reduced by about.... er........... nothing.

 

 

Gibbo

 

Isn't it the case that some alternators do use the same windings for both voltages, but change between star & delta configuration?

 

An awful lot of 'stuff' will be made in both voltages, to satisfy the commercial vehicle/vessel markets. OK that may not be true for some low-end domestic/pleasure boat stuff, and it's certainly true that many (UK, pleasure boat) chandlers won't keep much 24V stuff in stock.

 

As I see it, 24V is better theoretically, especially for boats of more than say 40' length and/or lots of gear, but it has practical snags with availability and sometimes price of equipment. It's a matter of personal judgement which to go for, I can understand why most will choose 12V.

 

Tim

[NB Alnwick]

There must be some advantages in using a higher voltage - otherwise why go to the bother of having high voltage electricity at all. If 12v DC really is the best answer - then why hasn't it been adopted as a safe standard for our mains supply?

 

The savings of 24v compared with 12v may well be minimal but then so are the savings gained from wiring the batteries properly and using the correct size of cable - any easily achieved saving on a boat must be worth the effort.

[DHutch]

Now if everyone switched to 24 volt it would be fine. Simpler for everyone involved. But that's never going to happen. So for the present 12 volt is, without any question, the more popular.

My opening gambit was that there where more 12v boats than 24v. And if you would drive my down to what i would recomend to job public, it would be to go with 12v.

- However, having being running a 24v boat for years, what i am saying is that i have never had a problem with it being less common that was anything more than a very slight inconvence. Like them only have two of a light i wanted four of that i wasnt in a rush for.

 

If your water pump fails you should have a contingency plan anyway. Ours is that the draincock had a lenght of flexable hose on it thats used for a sight glass, but if uncliped from the wall, can by lowered, at which point it would fill a pan/kettle/jug.

 

 

Daniel

[madcat]

For what its worth I think Im in the 12v camp for a modern leisure narrow boat due to 12v items being more common and 12v systems more usual on modern boats.The volt drop issue is solvable with a properly designed and well fitted installation with correctly sized cables and decent components which are fit for purpose. Strictly no bell wire !!!!.

If your engine is 24v for starting probably it wouldnt be so bad to fit a 2nd alternator delivering 12v for the domestic batteries..

In my case the boat had a 12v starter and was therefore all 12v had it been 24 v then thats how it would have stayed because the starter motor is probably the most expensive bit of electrical equipment to replace.Being an old boat with just back cabin and engine room theres not much electrics to worry about. Simples as the squeaky furry ones would say.

I think you probably want to enjoy your boat and boating and not get bogged down with complications so 12v would probably be the best bet as Gibbo says

[Yoda]

For what its worth I think Im in the 12v camp for a modern leisure narrow boat due to 12v items being more common and 12v systems more usual on modern boats.The volt drop issue is solvable with a properly designed and well fitted installation with correctly sized cables and decent components which are fit for purpose. Strictly no bell wire !!!!.

If your engine is 24v for starting probably it wouldnt be so bad to fit a 2nd alternator delivering 12v for the domestic batteries..

In my case the boat had a 12v starter and was therefore all 12v had it been 24 v then thats how it would have stayed because the starter motor is probably the most expensive bit of electrical equipment to replace.Being an old boat with just back cabin and engine room theres not much electrics to worry about. Simples as the squeaky furry ones would say.

I think you probably want to enjoy your boat and boating and not get bogged down with complications so 12v would probably be the best bet as Gibbo says

 

 

I refer you to post #60 Times are a'changing.

Edited August 31, 2009 by Yoda

[Gibbo]

There must be some advantages in using a higher voltage - otherwise why go to the bother of having high voltage electricity at all. If 12v DC really is the best answer - then why hasn't it been adopted as a safe standard for our mains supply?

 

The savings of 24v compared with 12v may well be minimal but then so are the savings gained from wiring the batteries properly and using the correct size of cable - any easily achieved saving on a boat must be worth the effort.

 

The advantage is thinner cables. There are no others of any significance.

 

If that is the deciding factor then yes, 24 volts is better because the cables are thinner.

 

But if being able to get a replacement pump on 5 minutes notice is more important then just put thicker cables in (four times the CSA) and use 12 volts.

 

There are of course other considerations. 24 volt TVs aren't as common for one.

 

Gibbo

 

Isn't it the case that some alternators do use the same windings for both voltages, but change between star & delta configuration?

 

I dunno. Snibble's the man to answer that one.

 

From a technical point of view it is certainly a possibility. But both the 12 and 24 volt units would be a bit of a compromise.

 

An awful lot of 'stuff' will be made in both voltages, to satisfy the commercial vehicle/vessel markets. OK that may not be true for some low-end domestic/pleasure boat stuff, and it's certainly true that many (UK, pleasure boat) chandlers won't keep much 24V stuff in stock.

 

As I see it, 24V is better theoretically, especially for boats of more than say 40' length and/or lots of gear, but it has practical snags with availability and sometimes price of equipment. It's a matter of personal judgement which to go for, I can understand why most will choose 12V.

 

That's exactly how I see it.

 

Gibbo

[nb Innisfree]

Gibbo answer the question, did you or did you not get out of the wrong side of the bed?

[Yoda]

Gibbo answer the question, did you or did you not get out of the wrong side of the bed?

 

 

What makes you think he gets out of bed?

[Gibbo]

Gibbo answer the question, did you or did you not get out of the wrong side of the bed?

 

Yes, but only because I slept in the wrong half.

 

Gibbo

[madcat]

Yoda I looked at post 60 once I realised that was what you meant,thought you was on about the 1960s at first but them Im only a cat! I think that 12v became the norm for narrow boats because of the influence of the caravan market,remember when everybody had labcraft strip lights.Things are indeed changing .My brand of "retro boating" is really a minority and most people want a few mod cons and why not.Wonder what the future holds but I hope it includes instant relief for toothache as I ve seen more than I care to of the emergency dental clinic this bank holiday and would much rather have been on the boat .

[GUMPY]

I know for certain that my local chandlery does not have 24 volt equipment on the shelves.

 

Your local chandlery, which is also mine, doesnt have much of anything on the shelves.

Possibly the worst chandlery in the world.

Me I use mail order or Uxbridge who do have a good stock of most things.

 

 

Oh and I am on the fence with this one having both a 24v system and a 12v system

Edited August 31, 2009 by idleness

[Guest]

Yoda I looked at post 60 once I realised that was what you meant,thought you was on about the 1960s at first but them Im only a cat! I think that 12v became the norm for narrow boats because of the influence of the caravan market,remember when everybody had labcraft strip lights.Things are indeed changing .My brand of "retro boating" is really a minority and most people want a few mod cons and why not.Wonder what the future holds but I hope it includes instant relief for toothache as I ve seen more than I care to of the emergency dental clinic this bank holiday and would much rather have been on the boat .

Possibly, but far more likely because nearly all the engines used are 12V based.

[alan_fincher]

Your local chandlery, which is also mine, doesnt have much of anything on the shelves.

Possibly the worst chandlery in the world.

Me I use mail order or Uxbridge who do have a good stock of most things.

I agree Uxbridge is good, and the other one we are talking about doesn't compete, (other than on convenience).

 

I don't agree it is close to "worst in the world" though - there are much worse.

 

You would certainly have no trouble sourcing a 12 volt water pump there, (or parts to service popular existing models), and a shower drain pump would be easy too.

 

Actually I find many needs can be met there, and although sometimes are very pricey, other times they are pretty competitive, (I couldn't beat their price on either a calorifier, or on a replacement Morco, or at least not if I factored in mail order carriage charges.)

 

Some chandleries, despite all the hype, may have keen prices, but actually have remarkably little choice. I mentioned one earlier that falls into that category, (in my opinion).

 

Ever tried going to Midland at Braunston for a list of things they say they have ? I did, and they hadn't!

[NB Alnwick]

>snipped<

Ever tried going to Midland at Braunston for a list of things they say they have ? I did, and they hadn't!

 

I've always found everything I need at Braunston - but then I am not looking for 12v items

[smileypete]

So, anyone know how much the cable costs for a typical 50-60' narrowboat?

 

 

I think, technicalities aside, that you will always find it easier to get 12V gear on the cut. I think most chandlers stock 12V pumps and suchlike. If say a water pump fails, or a shower drain pump, you will want a replacement pretty quickly. I would hedge my bets on obtainning a 12V one easier than a 24V one. Perhaps I am mistaken, but will stay with 12V.

Whale Gulpers last pretty much forever, also the 24V versions are fairly common and cheap off Ebay.

 

With water pumps it's usually the pump head that fails. If a 24V pump fails, the 12V equivalent can be bought and the pump head swapped over.

 

 

There is of course the question of the alternator, 24V ones at higher outputs are very definitely more efficient and if the OP as a liveaboard intends to use this form of charging a lot then over the lifetime of the boat, quite a bit of diesel could be saved.

By my reckoning a 24V alternator is at least 5% more efficient than a 12V one on rectifier losses alone.

 

cheers,

Pete.

[Guest]

I have come to the conclusion that the 24V business is definitely an elitist thing.

[alan_fincher]

I've always found everything I need at Braunston - but then I am not looking for 12v items

It's happened more than once, but on a classic occasion we went in for about 5 or 6 different things, all listed on their web-site, not one of which was in that branch.

 

So far as I recall, none was an electrical item.

 

They blamed stock-taking that time - presumably if you let your stock run down to zero, it's quicker to count things.

 

Not as bad as Limekiln, though, who we have twice contacted to establish that we are justified in making the trip. Having been told about batteries "don't worry, we always have a pallett", they had none (the main branch), and having enquired about specific lifejacket availability and being told "we always have those", they didn't (Stourport). Some exceedingly inaccurate "advice" about gas fitting too.

 

Disappointing really, but one gets to know the better ones.