12v or 24v?

[NorthwichTrader]

My apologies for asking this age-old question again, but you can't search 3 letter words on this forum to read others' previous contributions!

 

So, I've got a perfectly good 24v starter motor on my engine, which I would have to swap if I went for 12v just to keep the system simple.

 

Keep 24v or go for 12v, what's the general consensus?

[bottle]

Eerr!! would you not also need to change the alternator to 12v so as to be able to charge the start (12v) battery.

 

 

Aside, I have the opposite to you, boat is 24v, start (engine and generator) are 12v. Two alternators on engine one 12v and the other 24v, generator has one 12v.

[Timleech]

24V has definite advantages, especially if the boat is long and/or if you intend having a large inverter.

Main disadvantage is that you won't get many cheap deals from the chandlers and some items might have to be ordered in.

Look for commercial vehicle suppliers and proper marine, rather than canal, chandlers for a better chance of 24V stock.

Secondhand or old stock bargains are to be had in 24V if you keep a lookout on ebay etc.

 

Tim

[Speedwheel]

I know at least two people who have both. (In one case you can get 12v or 24v from the same sockets depending on how you wire the plug up)

[Paul C]

My apologies for asking this age-old question again, but you can't search 3 letter words on this forum to read others' previous contributions!

 

So, I've got a perfectly good 24v starter motor on my engine, which I would have to swap if I went for 12v just to keep the system simple.

 

Keep 24v or go for 12v, what's the general consensus?

 

Is the boat part way through a build? Brand new? etc

 

If you are, for example, building a sailaway and you've just fitted an engine with a 24V starter, then there's a good case for going "24V" throughout the boat. If you have an old boat with 12V electrics everywhere except you've just replaced the starter motor with the wrong one, then its a different matter.

[smileypete]

My apologies for asking this age-old question again, but you can't search 3 letter words on this forum to read others' previous contributions!

 

So, I've got a perfectly good 24v starter motor on my engine, which I would have to swap if I went for 12v just to keep the system simple.

 

Keep 24v or go for 12v, what's the general consensus?

Could be worth a go for the off-grid liveaboard boat cum power station

 

In that case it can be worth shopping around for occasional bargains on 24V alts, inverter, gulper, blown air heater, and 24V solar and wiring work out cheaper. The savings can then be ploughed back into more solar and bigger/better batts....

 

Balanced against that is the risk of having to pay a premium for 24V kit when it fails and replacement is urgently needed, though a few items like DC fridges, solar controllers are usually dual voltage.

 

Don't know if it's really needed for the average canal boat, more of a lifestyle choice maybe?

 

cheers, Pete.

~smpt~

Edited June 30, 2013 by smileypete

[mrsmelly]

Our boats at work have 12volt and 24 volt for various bits of kit and the leccy string runs are a hell of a lot longer than any narrowboat wiring and I can quite categoricaly state without hesitation that the 12volt kit works extremely well all of the time. I can also state that the 24volt kit works extremely well all of the time.

In the real world there is simply no difference and our boats get way more hammer than most.

 

Tim

[Timleech]

Our boats at work have 12volt and 24 volt for various bits of kit and the leccy string runs are a hell of a lot longer than any narrowboat wiring and I can quite categoricaly state without hesitation that the 12volt kit works extremely well all of the time. I can also state that the 24volt kit works extremely well all of the time.

In the real world there is simply no difference and our boats get way more hammer than most.

 

Tim

 

Of course there is a difference, the wiring for 12Volt needs to have double the cross-sectional area of that for 24V for the same performance.

The amount of 'hammer' should make no difference if the system is properly designed and built.

Personally I'm not keen on the scale of currents and wiring needed to cope, for big (say 3kW) 12 Volt inverters. Yes it can all be done but I'd rather avoid having to do it.

 

Tim

[ditchcrawler]

Eerr!! would you not also need to change the alternator to 12v so as to be able to charge the start (12v) battery.

 

 

Aside, I have the opposite to you, boat is 24v, start (engine and generator) are 12v. Two alternators on engine one 12v and the other 24v, generator has one 12v.

I'am the same, It seemed a good idea at the time while talking to a mate in a pub.

[Charlotte Burnett]

I rewired with a 3kw inverter in 12v, wouldn't again. As has been said, 24v makes more sense for big boats/big systems. Everything works just fine with 12v but handing the cable is hard work and it's sodding expensive!

[mrsmelly]

 

Of course there is a difference, the wiring for 12Volt needs to have double the cross-sectional area of that for 24V for the same performance.

The amount of 'hammer' should make no difference if the system is properly designed and built.

Personally I'm not keen on the scale of currents and wiring needed to cope, for big (say 3kW) 12 Volt inverters. Yes it can all be done but I'd rather avoid having to do it.

 

Tim

Hi

 

The physical difference in cable sizing is no big deal, we are not talking 20mm cross section after all. Our boats at work and my private boat are all wired with much much bigger stuff than is quoted as necessary it simply removes any chance of voltage drop now or in the future if very big cable is installed from day one. The fact is that 12 volt stuff and 24 volt stuff both work equaly as well when installed correctly and as for big inverters? one of our boats has four 3kw 12 volt inverters and one has 3 by 3kw 24 volt inverters and they both do their work without any noticeable difference.

One boat has 12 volt starter motors and the other has 24 volt motors and both spin the engines in precisely the same way without any problem etc etc.

We have many wiring runs of over 100 feet in length with no problems whatsoever. Incidentaly we have morso cables of 20 metres in length on one boat and after 35000 hours of use since 1997 they have never failed and are original which does astound me somewhat !!

 

Tim

[Guest]

Can't see the real concern over the wiring for an inverter at 12V. Best to put the inverter next to the batteries if possible, so they will be short anyway. My 3Kw inverter seems to soldier on OK at 12V after almost ten years.

[NorthwichTrader]

Wow, thanks for all your input!

 

I should perhaps expand, as I can see it'll make a difference...the engine is not yet in the boat, which will be a 70ft sailaway (so longish wire runs), and doesn't presently have an alternator fitted. So, at this stage, we could go 12 or 24, with the first issue being whether I should be looking for a 12v starter motor, or sticking with the 24v starter that's fitted?

Is there any modern trends towards one or the other?

[Paul C]

I'd say its worth a detailed calculation: work out the costs of the wire for 12V, then the cost of wiring at 24V (for example, thinner main runs for lighting, thinner fridge supply, thinner wires for inverter if you have one, etc).

 

Then work out the possible extra cost of 24V electrical items instead of 12V. For example alternator, starter motor, fridge, lighting, TV. If you can't find an equivalent item, then you'll be into possibly a 24VDC - 12VDC converter, or using a mains powered item and committed to the inverter.

 

Assuming you were going to fit an even number of domestic batteries, then the cost here is the same. But you might need to allow for fitting 2x small 12V starter batteries in series, for the 24V route.

 

Given that you're starting from a 'clean sheet', I'd recommend either/or, not a mix of 12V engine and 24V domestic or vice versa, the reason being one day you might need to jump start the engine starter off the domestic battery bank. You don't want to be disconnecting and rearranging batteries to allow this.

[MtB]

It's an impossible question to sensibly advise on without detailed info about all the electrical kit you plan to fit, your intended cruising style/pattern, the engine you will be fitting, your attitude to costs, and a million other details!

 

 

MtB

[NorthwichTrader]

I'd say its worth a detailed calculation: work out the costs of the wire for 12V, then the cost of wiring at 24V (for example, thinner main runs for lighting, thinner fridge supply, thinner wires for inverter if you have one, etc).

 

Then work out the possible extra cost of 24V electrical items instead of 12V. For example alternator, starter motor, fridge, lighting, TV. If you can't find an equivalent item, then you'll be into possibly a 24VDC - 12VDC converter, or using a mains powered item and committed to the inverter.

 

Assuming you were going to fit an even number of domestic batteries, then the cost here is the same. But you might need to allow for fitting 2x small 12V starter batteries in series, for the 24V route.

 

Given that you're starting from a 'clean sheet', I'd recommend either/or, not a mix of 12V engine and 24V domestic or vice versa, the reason being one day you might need to jump start the engine starter off the domestic battery bank. You don't want to be disconnecting and rearranging batteries to allow this.

Thanks, Paul! I totally agree with you on an either/or scenario, I don't want a split system!

We'll be liveaboard and wanting to make the boat off-grid friendly, so will be looking at solar in good time. I noted someone mentioned (Smiley Pete, I think - can't check, now I'm posting on the iPhone?) that 24v was advantageous for solar, so maybe it's the way to go?

I know we could be asking a lot, but a really good (and spacious, and probably thirsty) fridge-freezer is top of our list!

[Guest]

Having seen the price of starter motors for some engines recently, your decision might already have been made for you! You would need to check it out though.

[NorthwichTrader]

It's an impossible question to sensibly advise on without detailed info about all the electrical kit you plan to fit, your intended cruising style/pattern, the engine you will be fitting, your attitude to costs, and a million other details!

 

 

MtB

That's a fair comment!

We had originally intended to be totally off grid and tramp the waterways in idle bliss, whilst home-schooling our 5-year-old son!

However, his social integration has had us rethink the strategy a bit, and have since opted for a marina base (for now), though we still want the boat with full off-grid capability (solar, generator, etc.)

We will essentially be living in a lined and compartmented wooden tube, with a portaloo in the engine room (until we get the toilet fitted), and a bucket for a sink, until we can work through our actual needs for the boat.

We've got a Kelvin J3 and a fitted boatman's, so we will have at least one decent bed to start with.

It's a new build, and we are right at the beginning of the project, and our learning!

We have probably got around £4k to make a start on the fit out, so we'll need to prioritise, but we'd always prefer to wait until we've got the full amount for something, rather than settle for something we'd forever grumble about in the future!

We're looking for peace and tranquility, that's more or less where we're coming from!

PS I Enjoyed your you-tube footage, I'm guessing that was you?

[MtB]

Prolly yes, my youtube channel has about nine vids of my Kelvin K1

 

Given yer budget for fitting out is hopelessly, unrealistcally low I suggest 12v is the only way to go. 12v will start a J3 perfectly but don't be a wuss, start it by hand - you know it makes sense!

 

 

 

MtB

[NorthwichTrader]

Prolly yes, my youtube channel has about nine vids of my Kelvin K1

 

Given yer budget for fitting out is hopelessly, unrealistcally low I suggest 12v is the only way to go. 12v will start a J3 perfectly but don't be a wuss, start it by hand - you know it makes sense!

 

 

 

MtB

Edit: once we get on the boat, it should also free up around £700 PM

Edited June 30, 2013 by NorthwichTrader

[Charlotte Burnett]

Given your situation, I see no advantage to going 12v beyond availability of spares. I don't see this as a massive issue; what is going to go wrong? Water pump? The rebuild kit is similar for 12 and 24v. Central heating pump? You have a spare plumbed in parallel right? Tunnel light bulb? Keep a spare. Truck place would keep one anyhow. Whale gulper? I'm sure they have failed before but I've not heard of it! Cabin lights? They'll be LED with wide input voltage and last until your 5 year old has left home. Almost all of the 12v stuff retails for the same as 24v. If there is a specific thing that is particularly overpriced, there is the option of using a DC-DC converter to step the voltage down.

 

If I read correctly, you have a 24v starter motor already and £4k for a fit out - I'd rather have a bathroom than a 12v starter motor. 24v makes for potentially a cheaper solar installation as you will run at half the current of 12v for the same given number of cells which means to can fit a regulator of half the size necessary for a 12v system.

[smileypete]

Maybe just do a quick spreadsheet for comparison of 12V vs 24V costs?

 

Might be possible to get the starter rewound for 12V too, or in the meantime use a 2ndhand batt to give 24V for starting from 12V bank, charge it from a solar or DC converter or something.

 

cheers, Pete.

~smpt~

Edited June 30, 2013 by smileypete

[MtB]

I disagree. It's not just the cost but the availability. 12v water pump failed? On the shelf in Midland Chandlers. 24v pump failed? Fat chance, a two week wait to order one and twice the price I bet. Same story with everything else. You HAVE to think ahead and keeps spares in stock for EVERYTHING, which means buying twice, in effect.

 

You'll regret go 24v I predict, but this is just my opinion.

 

MtB

[NorthwichTrader]

Many thanks Charlotte Burnett, and to everyone else who've kindly posted!

I have to say, the thought of sourcing a new starter, brackets, and possibly a new engine mount, is beginning to turn the tide a bit, particularly with such an evenly weighted contest between the two wiring systems!

Thanks again!

[MtB]

Many thanks Charlotte Burnett, and to everyone else who've kindly posted!

I have to say, the thought of sourcing a new starter, brackets, and possibly a new engine mount, is beginning to turn the tide a bit, particularly with such an evenly weighted contest between the two wiring systems!

Thanks again!

 

With a J3 you don't need a starter motor at all!

 

MtB

 

P.S. I have 24v starter on Aldebaran, 24v alternator, 12v domestic system and a 24v to 12v step-down device to charge the 12v domesic batts from the 24v alternator