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20 minutes ago, Boater Sam said:

The BIG question.......................... How do you know you have a 24v system? Exactly what is running off 24v? Engine?  cabin lights?  pumps?

The BIG question.......................... How do you know you have a 24v system? Exactly what is running off 24v? Engine?  cabin lights?  pumps? Battery charger? Inverter?

Could you be mistaken and its all 12v and a muppet has paired the batteries to give 24v?

The sales details for the boat are easily found online.

 

Rugby boats claimed it has....

 

ALB135A 24V alternator (new 2017)

 

4 * 110AH Domestics, 1 * 96A Starter

 

Mastervolt Mass 2500W/24V/60A Inverter with Mastervolt conroller (Presumably inverter charger combi?),

 

Assuming they are vagely accurate, this does look like a boat with 24 volt domestic electrics.

 

That said it is a Floating Homes 57 foot boat from 2003.  I would have thought a 24 volt electrical system on a boat from Floating Homes that has a Perkins Priima is a fairly unuual beast, isn't it?

 

As someone said a 24V alternator on an engine with a12 volt starter is clearly not an original fit.

 

 

Edited by alan_fincher

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I am puzzled as to why my betters are puzzled by the difficulties in charging a 12v (starter) battery from a 24v alternator/domestic system.  Could you not just put the starter battery in parallel with one of the two batteries making up the 24v (i.e. centre tap)?  A switch or gizmo in the connection could prevent the domestic side from draining the starter battery. 

 

I am not, of course,  saying this is how the OPs boat is wired - just asking if it can't be done quite simply. 

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12 minutes ago, Tacet said:

I am puzzled as to why my betters are puzzled by the difficulties in charging a 12v (starter) battery from a 24v alternator/domestic system.  Could you not just put the starter battery in parallel with one of the two batteries making up the 24v (i.e. centre tap)?  A switch or gizmo in the connection could prevent the domestic side from draining the starter battery. 

 

I am not, of course,  saying this is how the OPs boat is wired - just asking if it can't be done quite simply. 

I did suggest that possibility in post 39 ?

Edited by Eeyore

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15 minutes ago, Tacet said:

I am puzzled as to why my betters are puzzled by the difficulties in charging a 12v (starter) battery from a 24v alternator/domestic system.  Could you not just put the starter battery in parallel with one of the two batteries making up the 24v (i.e. centre tap)?  A switch or gizmo in the connection could prevent the domestic side from draining the starter battery. 

 

I am not, of course,  saying this is how the OPs boat is wired - just asking if it can't be done quite simply. 

Yes it can be done. It’s very poor practise and can unbalance the domestic bank. 

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1 minute ago, WotEver said:

Yes it can be done. It’s very poor practise and can unbalance the domestic bank. 

^^^^^^^^^^^^
This.

 

It's possible, but a bad idea.

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24 volt alternator marine double insulated,  exciter circuit triggered from relay operated by starting circuit .

 

24 volt inverter 

 

12 volt battery and starter insulated from 24 system

step down transformer 24 volt to 12 volt to charge start battery.

 

leave in marina plugged in... 

finaly goes boating and transformer/ inverter drains 24 batts when the alternator pops and fails to charge , or someone fails to follow some strange isolating procedure.

 

given boat appears very mains dominated the builder may gave fitted all 24 volt plus a step down circuit for pumps etc.

 

nightmare

 

 

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57 minutes ago, WotEver said:

Yes it can be done. It’s very poor practise and can unbalance the domestic bank. 

Isn't that similar to what happened with big-Col (and destroyed his batteries) ?

  • Greenie 1

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1 hour ago, WotEver said:

Yes it can be done. It’s very poor practise and can unbalance the domestic bank. 

OK - but it is much simpler than the other suggestion of 24v inverters powering 12v battery charges.

 

If the only real problem is with balancing the draw on the batteries, the power drawn by topping-up the starter will usually only be a few ah per day.   Gibbo did some calculations showing how differing length links/resistances on parallel batteries caused some to draw more current than others.   But as he acknowledged, he did not allow for the batteries equalizing voltages (and therefore SoC) when not much else was happening  current-wise.  I was never greatly convinced it was a real-world issue any more than say, some batteries might be better cooled by being further from the engine or the difference between middle and end batteries in a closely packed bank.

 

Years ago a friend had a Transit van with a York engine, which were notoriously difficult to start.  So, amongst other fixes, a second battery was added in parallel.  When he went camping (several tents.....) the batteries were connected in series to run a 24v system on a -12v - 0v - +12v arrangement using round pin 15a and 5a plugs depending on whether it was 12v or 24v at that point.   He tied a label on the steering wheel to remind him to change back to parallel  and, as far as I know, never discovered what happened when you put 24v to the van's electrics.

 

 

 

 

 

Edited by Tacet

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54 minutes ago, roland elsdon said:

24 volt alternator marine double insulated,  exciter circuit triggered from relay operated by starting circuit .

 

24 volt inverter 

 

12 volt battery and starter insulated from 24 system

step down BUCK MODULE  24 volt to 12 volt to charge start battery.

 

leave in marina plugged in... 

finaly goes boating and transformer/ inverter drains 24 batts when the alternator pops and fails to charge , or someone fails to follow some strange isolating procedure.

 

given boat appears very mains dominated the builder may gave fitted all 24 volt plus a step down circuit for pumps etc.

 

nightmare

 

 

Slipped in a correction, transformers are for AC only but a buck module like   Big Col used will do it.

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1 hour ago, Alan de Enfield said:

Isn't that similar to what happened with big-Col (and destroyed his batteries) ?

Yes. 

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1 hour ago, Tacet said:

If the only real problem is with balancing the draw on the batteries, the power drawn by topping-up the starter will usually only be a few ah per day. 

Then the next day. Then the next day. And on the day that the engine is reluctant to start it becomes a lot more than a ‘few’ Ah. BigCol successfully destroyed a pair of batteries doing that quite recently as Alan noted above. Think about the voltage across each of the 12V Batteries in series with 29V across the pair, when the ‘bottom’ battery is depressed by a flattened starter battery. 

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35 minutes ago, WotEver said:

Then the next day. Then the next day. And on the day that the engine is reluctant to start it becomes a lot more than a ‘few’ Ah. BigCol successfully destroyed a pair of batteries doing that quite recently as Alan noted above. Think about the voltage across each of the 12V Batteries in series with 29V across the pair, when the ‘bottom’ battery is depressed by a flattened starter battery. 

Well, it's a matter of degree so there can be no absolute answer.  If you flatten the single domestic, it is going to subsequently have a greater rater of charge than its series friend, but any more than a single flat battery on a 12v system?

 

But assuming the domestic and starter batteries are only paralleled when the alternator is charging,  the drop in voltage on the single domestic is not going to be that great.  If you had a VSR, would it not prevent the domestic being caned too hard? (honest question).

 

If you were that bothered, you could rotate the domestic battery so each had its turn being paralleled with the starter. 

 

  

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Just now, Tacet said:

If you flatten the single domestic, it is going to subsequently have a greater rater of charge than its series friend, but any more than a single flat battery on a 12v system?

Yes, because you’re not thinking about the ‘top’ battery that is now being seriously over-voltaged. This is what happened to Col. 

2 minutes ago, Tacet said:

If you were that bothered, you could rotate the domestic battery so each had its turn being paralleled with the starter. 

You could yes, far better to organise a more elegant solution so that you don’t have to. 

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14 hours ago, Boater Sam said:

Slipped in a correction, transformers are for AC only but a buck module like   Big Col used will do it.

Thank you, im anything but a physicist or engineer, just trying to work out what could have been done ..

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I came across a similar fudge a few years ago, new boat with domestics going flat overnight. Turned out to save on decent bowthruster cable the builder put a mains charger in the bow area to charge bowthruster , connected to inverter . As a result overnight it dumped all the domestic capacity into the bowthruster batterys.

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4 hours ago, roland elsdon said:

...just trying to work out what could have been done ..

Sadly, it seems to me there's a fair chance its the OP that could have been done!

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27 minutes ago, Sea Dog said:

Sadly, it seems to me there's a fair chance its the OP that could have been done!

Yes but im starting from having owned/ lived on 5 different boats since 1980 and done a lot of work ( as an amateur) to many.

only as i work towards changes on my own boat do i realise how little i know.

i seem to have missed from about 2000 to 2018 in technological changes...

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 I have just read on Facebook a boater with a single alternator, 12 volt this time feeding his domestics and the started being served by an A to B charger. can you get a 24 to 12 A to B ?

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1 hour ago, ditchcrawler said:

 I have just read on Facebook a boater with a single alternator, 12 volt this time feeding his domestics and the started being served by an A to B charger. can you get a 24 to 12 A to B ?

I wonder if he meant B to B? Sterling sell those. 

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2 hours ago, ditchcrawler said:

 I have just read on Facebook a boater with a single alternator, 12 volt this time feeding his domestics and the started being served by an A to B charger. can you get a 24 to 12 A to B ?

Don't some folks just love to unnecessarily complicate simple things.

 

Yes 24v to 12v dropper is what we suggested Col got for his system after his 'super dooper' splitter device cooked his batteries.

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I have lost track of the topic more than a bit but it its a 24V engine system and 12V domestics then I doubt anything like Col bought would have enough output.

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On 13/02/2019 at 11:29, roland elsdon said:

 

step down transformer 24 volt to 12 volt to charge start battery.

 

 

See transformers don't work on DC, only in A.C.. 

 

A 24-12 volt buck boost converter would do the job though.

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10 minutes ago, cuthound said:

A 24-12 volt buck boost converter would do the job though.

Just a buck. No boost required. 

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