Live aboard electrics

[melkaren]

Any opinions on our proposed electrical system for a 65 ft full time live aboard

 

here is what we have been advised:

 

Beta 43 engine

 

12volt DC 45 amp alternator for starter battery and bow thruster batteries

24 volt DC 75 amp alternator for battery pack(660AH) plus 3Kw/70amp/24v Victron inverter/charger

Fischer Panda 4000i 7.0 kva AC generator

 

Will be running at 230 volts AC, washing machine, small tumble dryer, micro-wave, iron (not all at once)

 

Would appreciate any suggestions or alterations

[pagan witch]

Any opinions on our proposed electrical system for a 65 ft full time live aboard

 

here is what we have been advised:

 

Beta 43 engine

 

12volt DC 45 amp alternator for starter battery and bow thruster batteries

24 volt DC 75 amp alternator for battery pack(660AH) plus 3Kw/70amp/24v Victron inverter/charger

Fischer Panda 4000i 7.0 kva AC generator

 

Will be running at 230 volts AC, washing machine, small tumble dryer, micro-wave, iron (not all at once)

 

Would appreciate any suggestions or alterations

 

 

Seems to me like a whole lot of electrical power there - are you sure it is a boat you are planning ?

 

Unless you are going all electric and forgot to mention it why the 7 kva gen set ? That equates to over 30 amps at 240 volts - enough to run most domestic sized electric ovens.

 

We are normally connected to shore line granted, but even so with the exception of the washing machine we can run everything else off of the 2kw inverter and a 440 ah battery bank. If we want the washing macine we run a diesel 2.5 kva gen set that lives under the back deck.

 

PS what is 'an iron' ? see similar thread

[melkaren]

Does this help???

 

http://en.wikipedia.org/wiki/Ironing

[Gibbo]

Any opinions on our proposed electrical system for a 65 ft full time live aboard

 

here is what we have been advised:

 

Beta 43 engine

 

12volt DC 45 amp alternator for starter battery and bow thruster batteries

24 volt DC 75 amp alternator for battery pack(660AH) plus 3Kw/70amp/24v Victron inverter/charger

Fischer Panda 4000i 7.0 kva AC generator

 

Will be running at 230 volts AC, washing machine, small tumble dryer, micro-wave, iron (not all at once)

 

Would appreciate any suggestions or alterations

 

That's a nice system but is it really necessary? That is one HUGE battery bank. 12 typical sized batteries as opposed to the usual 3, 4 or 5. And a 75 amp alternator into a bank that size isn't really big enough in my opinion. I'd be wanting something closer to 150 or even 200 Amps.

 

Unless, of course, someone has thought that 6 X 100Ahr batteries wired up as 24 volts gives 600 Ahrs. That changes the whole perspective.

 

Gibbo

[chris w]

Any opinions on our proposed electrical system for a 65 ft full time live aboard

 

here is what we have been advised:

 

Beta 43 engine

 

12volt DC 45 amp alternator for starter battery and bow thruster batteries

24 volt DC 75 amp alternator for battery pack(660AH) plus 3Kw/70amp/24v Victron inverter/charger

Fischer Panda 4000i 7.0 kva AC generator

 

Will be running at 230 volts AC, washing machine, small tumble dryer, micro-wave, iron (not all at once)

 

Would appreciate any suggestions or alterations

 

Can you confirm. You have a 24v 660AH battery bank (ie: 12 x 12v 110AH batteries) or you have 6 x 12v 110AH batteries wired to give 24v, which would be 330AH?

 

Chris

[melkaren]

Chris

 

Quoted as '2x 320 amp-hour full traction battery pack, giving 320 amp-hrs at 24 volts' I may have got the original info wrong...

 

Does this assist ?

[chris w]

OK yes that's a 24v 320AH set up. Why have you gone for 24v rather than 12v? Getting suitably rated equipment will be always more problematic with 24v. In case you are not aware, you could wire the batteries in parallel and ahave a 12v 640AH bank.

 

Chris

Edited March 24, 2008 by chris w

[blackrose]

Can you confirm. You have a 24v 660AH battery bank (ie: 12 x 12v 110AH batteries) or you have 6 x 12v 110AH batteries wired to give 24v, which would be 330AH?

 

Chris

 

If it's the former that's a whole lot of battery maintainence - 72 cells to top up and that's not including the start or BT batteries.

 

I thought the Fischer Panda 4000i was a 4kw generator - where does the 7kva come from?

http://www.mymarina.co.uk/Boat_News/BoatNe...da-pms400i.html

[melkaren]

Apologies re genny got that wrong too, yes it is a 4kw

 

I know very little about electrics...believe 24volt was due to voltage drop

[blackrose]

Apologies re genny got that wrong too, yes it is a 4kw

 

I know very little about electrics...believe 24volt was due to voltage drop

 

Depending on how the battery bank is configured I think it sounds like a good system, although I think your alternators could be a bit bigger.

[chris w]

Apologies re genny got that wrong too, yes it is a 4kw

 

I know very little about electrics...believe 24volt was due to voltage drop

 

24v will have less voltage drop (50% of 12v for the same cable diameter). BUT, this is a normal phenomenon to overcome in boat electrics and is easily solved by doubling the cable cross-sectional area compared to that used for 24v. Doubling the cross-sectional area though doesn't mean that the cables are huge because to double the area, the diameter only has to increase by 1.4 times. Most cables on 12v systems are still fairly small diameter.

 

I would advocate going for a 12v system as you will have no issues in finding equipment to run on this. Could the real reason be that the boatyard that sold it to you wanted to get rid of their only 24v alternator??

 

I'll re-emphasise what I said above. Voltage drops on a 12v system are no problem. Cables sizes are simply chosen to suit.

 

Chris

[blackrose]

24v will have less voltage drop (50% of 12v for the same cable diameter). BUT, this is a normal phenomenon to overcome in boat electrics and is easily solved by doubling the cable cross-sectional area compared to that used for 24v. Doubling the cross-sectional area though doesn't mean that the cables are huge because to double the area, the diameter only has to increase by 1.4 times. Most cables on 12v systems are still fairly small diameter.

 

I would advocate going for a 12v system as you will have no issues in finding equipment to run on this. Could the real reason be that the boatyard that sold it to you wanted to get rid of their only 24v alternator??

 

I'll re-emphasise what I said above. Voltage drops on a 12v system are no problem. Cables sizes are simply chosen to suit.

 

Chris

 

Why do many bigger boats and Dutch Barges have 24v systems Chris? At the last London Boat Show a guy on the Kabola stand told me he was surprised that a boat the size of mine had a 12v system. They only supply 240v AC and 24v DC diesel heaters.

[chris w]

In essence there is no reason other than the voltage drops on a 24v system are half those of a 12v system for the SAME cable size. And, as I said above, if you increase the cable DIAMETER by a factor of 1.4 times (ie: doubling the cross-sectional area of the cable) the voltage drop on the 12v system will be the same.

 

The main reason they are saying what they're saying IMHO is that the vast majority of "professionals" don't know this or even know how to work it out. As we all know 24v stuff is no way as prevalent or as easy to find as 12v stuff.

 

Chris

[davidandheather]

This may be of interest

At a given power rating a 24 volt inverter will need half the current as a 12 volt inverter. This makes the entire system more efficient, and since high current transistors are expensive, the inverter will be cheaper. Many trucks and busses run their complete electrical systems on 24V.

David

[melkaren]

The only equipment running on 24 volt DC would be a fridge/freezer and lights, I have no problem sourcing those

Plus of course the invertor

Edited March 24, 2008 by melkaren

[chris w]

This may be of interest

At a given power rating a 24 volt inverter will need half the current as a 12 volt inverter. This makes the entire system more efficient, and since high current transistors are expensive, the inverter will be cheaper. Many trucks and busses run their complete electrical systems on 24V.

David

 

Huh??? The power will be the same in both cases. Twice the volts x half the current = the same number. The inverter power loss will also be the same percentage in both cases.

 

 

Melkaren:

 

The only equipment running on 24 volt DC would be a fridge/freezer and lights, I have no problem sourcing those

Plus of course the invertor

 

What about pumps, TV, radio etc

 

Chris

Edited March 24, 2008 by chris w

[Nickhlx]

The Beta 43 and 50 are currently coming with a 12 volt, 150 and a 45 amp alternator according to their brochure. Perhaps there is a 24 volt set you have opted for.

 

Also, wouldn't Peukert advocate configuring the batteries as a bigger AH ( lower voltage ) configuration for more effective capacity ?

 

 

Nick

[sueb]

Huh??? The power will be the same in both cases. Twice the volts x half the current = the same number. The inverter power loss will also be the same percentage in both cases.

Melkaren:

What about pumps, TV, radio etc

 

Chris

 

phone charger; computer.

The more batteries the more it's going to cost when they need replacing.

Sue

[melkaren]

Pumps 24 volt...no problem to source

TV, computer, phone charger...230 volt AC

radio: 1.2v Nimh re-chargable

[Tony Brooks]

Why do many bigger boats and Dutch Barges have 24v systems Chris? At the last London Boat Show a guy on the Kabola stand told me he was surprised that a boat the size of mine had a 12v system. They only supply 240v AC and 24v DC diesel heaters.

 

 

 

Possibly because the larger engines means that it would probably use 24 volt electrics in its native form to minimise the size of conductors in the starter etc.

 

Once you get into 24 volt starting it makes things a lot simpler to keep the whole boat as 24 volt. However I would stick with 12v on a narrowboat.

[sueb]

Pumps 24 volt...no problem to source

TV, computer, phone charger...230 volt AC

radio: 1.2v Nimh re-chargable

 

Why use more power to get 240v whe you only need 12v. You are just going to flatten your batteries and have to use diesel (at road prices soon) to recharge them.

Sue

[blackrose]

Why use more power to get 240v whe you only need 12v. You are just going to flatten your batteries and have to use diesel (at road prices soon) to recharge them.

Sue

 

Because most 12v appliances are more expensive, not as readily available and not as good as mains appliances perhaps? Most boats have mains rings & inverters these days. You might use 10% more power just to run your inverter but if you're using two appliances then this inefficiency is halved and so on.

Edited March 24, 2008 by blackrose

[Gibbo]

Another common misconception has cropped here with regard to the difference between 12 and 24 volt systems and their required cabling sizes.

 

For the same power, a 24 volt item will use half the current of the equivalent 12 volt unit. This is obvious.

 

It therfore follows that using the same size cable will result in half the voltage drop. So that naturally leads to the idea that we use a cable with half the cross sectional area. This results in the same voltage drop on 24 volts as would be got on 12 volts. And that's as far as most people go. 24 volt can use half the cable size.

 

But think about that..... "the same voltage drop on half sized cable"..... Dropping 0.6 volts on a 24 volt system is only half as bad as dropping 0.6 volts on a 12 volt system (2.5% as opposed to 5%).

 

A 24 volt system can use cable of a "quarter" the cross sectional area of a 12 volt system for the same equivalent loss.

 

Gibbo

[chris w]

Well done that man. Having not ever run calculations for 24v systems, the penny hadn't dropped that not only is the current halved (that penny had dropped) but that the allowable voltage drop (say 3%) would of course double, numerically, resulting in a factor of x4 as compared to 12v systems. Thanks for pointing that out. So the cable diameters on a 24v system, as compared to a 12v system, will be halved. That's quite a reduction in size.

 

Chris

[Neil.A]

Pumps 24 volt...no problem to source

TV, computer, phone charger...230 volt AC

radio: 1.2v Nimh re-chargable

So, you want to make the same mistake as me eh?... I thought having a large battery bank and a Victron Inverter/charger and Dometic travel power would enable me to run fridges, dishwashers, TVs, DVD's etc. It does, but its a lot of un-necessary work. Why generate 12v to convert to 240v when you dont need to. Most TV's now have a 12v input and have Freeview and DVD's built in.

Listen to the advice already given on here, stick to 12v.