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BARGES: All about barges and barging - building, buying, maintaining, equipment, handling on the water, etc.
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TOPIC: 24V starter - 12V alternator !

24V starter - 12V alternator ! 28 May 2020 13:10 #116290

  • Pete Milne
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Cable size is a very good point here, thanks! With the Engine battery within a metre of the starter, it's easy to just double the cable capacity.
I'm not sure that starting with 12V (with a high-current battery like the Optima) is likely to be a problem. I suspect many old engines, like my DAFs were taken off lorries with the 24V starter and the batteries added instead of changing the starter. I'm sure most barges will be 24V for that as much as any other reason. I wonder how many others have 12V starters?

Pete

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Pete Milne, Quo Vadis , Gent.

24V starter - 12V alternator ! 28 May 2020 12:00 #116284

For a 12V starter to be the same power as 24v starter it will draw twice the amperage, therefore the cabling sized for a 24v starter may be too small for the 12v starter, which could lead to hot cables and poor turning power at the starter. Whichever way you go you will need to ensure that the starter in the same power as the original. Its not just by accident that trucks and heavy engines are 24v, 24v gives much better starting performance especially when turning over a cold heavy diesel first thing in the morning and probably the reason why such a complex system was installed in the first place.

take for instance a 4kw starter, at max load at 24v it will draw 166 amps, at 12v, 333 amps.
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24V starter - 12V alternator ! 27 May 2020 22:47 #116272

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Gordon Mackenzie wrote: Just my little bit of input , I can’t see if you are on 2 separate banks for starting and house or all in one , which is not a good idea, we have 24 volt starter and 12 volt alternator, however ,we have separate banks, 24v batteries for starting powered by a 12 to 24 v battery charger by Sterling ,so alternator charges 12volt l......../quote]
I bought the boat with one big 24V bank and the 12V alternator and 12V domestic distribution. As a neighbour pointed out while discussing it , replacing the 24V starter by 12V saves the cost of a second starter battery and gets rid of the historic 24/12V conversion kit and the cost of replacing it. Altogether simpler and if I cost in the price of a fit-and-forget Optima starter battery, it saves money, too. My only problem is access to the starter - and for the moment, getting across the border to Holland to collect a replacement! As I said earlier, time to bite the bullet and get the 24V starter out!
I am of course installing a separate 12V bank for domestic use , with a Cyrix to share charging in either direction. Solar panels too, of course.

Pete

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Pete Milne, Quo Vadis , Gent.

24V starter - 12V alternator ! 27 May 2020 11:41 #116261

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Just my little bit of input , I can’t see if you are on 2 separate banks for starting and house or all in one , which is not a good idea, we have 24 volt starter and 12 volt alternator, however ,we have separate banks, 24v batteries for starting powered by a 12 to 24 v battery charger by Sterling ,so alternator charges 12volt lithium’s via a BMS that can operate a relay to stop charging when full they in turn power the charger that will only switch on when the house batteries reach a predetermined voltage , this also is done by the solar as well so hopefully shouldn’t have any problems.
Cheers
Gordon
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24V starter - 12V alternator ! 27 Apr 2020 13:07 #115575

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Balliol Fowden wrote: Trevor, just hypothetically, yes, if everything else is 12 volt then a 12 volt starter is a no-brainer and, if access to the starter is difficult to change it, then that needs dealing with anyway.

There is nothing wrong with the principle of a series/parallel changeover, just the fact that the OP’s unit was clearly a museum piece and probably full of resistances and life expired coils, hence my suggestion to bin it, plus the separate fact that there is no split battery system.

That's exactly my thinking and conclusion after this discussion! If the Starter was as accessible as on a bigger barge, I'd change it in a flash. Also, if you can't get at something, it's sure to be the next thing to fail so I have tojust bite the bullet and rebuild part of engine room to deal with it. Then I'll have a nice simple system that can share all the charging sources (Alternator, Solar panels, Gen, Shore) with a simple split-charge relay (as well as the usual blue boxes!) and a single starter battery.
Thanks all - and if anyone needs a 'magic box' I'll have one going spare soon - but it may be better in a musem!

Pete

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24V starter - 12V alternator ! 27 Apr 2020 10:05 #115574

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Trevor Glave wrote: Pete, may I suggest you figure out how your magic box works its magic. You may then learn to eventually love it for what it does! This would be my second choice. My first choice would be to change the 24V starter to 12V as your neighbour suggests. An alternator/starter shop may be able to rebuild your 24V unit as a 12V unit cheaper than buying a new starter. (Is there actually a problem with your electrical system other than your ‘hate-at-first-sight’ magic box?) I presume that the PO installed what you have as his best solution. You have the usual 12V alternator and 12V load (lights, VHF etc.). The only unusual feature is a 24V engine starter. The magic box is a simple way to make this equipment work together. Simple is good!

Here’s how the magic box works. It just contains three high-current relays and has to be connected to two 12V batteries. Normally the two batteries (A & B) are connected in parallel by the relays in the box and are kept charged by the 12V alternator as usual. When you turn the key to operate the 24V starter the magic box leaves battery A connected as before but battery B gets its connections moved. Its negative terminal gets connected to the positive terminal of battery A and its positive terminal gets connected to the starter solenoid so the two batteries are now in series to apply 24V to the starter. When you release the key the box puts the batteries back in parallel. Balliol’s diagram may help understand your rat’s nest?

Does your new old toy use one battery bank for both domestic use and engine start? Not a good idea for at least two reasons!
Trevor


Trevor, just hypothetically, yes, if everything else is 12 volt then a 12 volt starter is a no-brainer and, if access to the starter is difficult to change it, then that needs dealing with anyway.

There is nothing wrong with the principle of a series/parallel changeover, just the fact that the OP’s unit was clearly a museum piece and probably full of resistances and life expired coils, hence my suggestion to bin it, plus the separate fact that there is no split battery system.

The SP unit could be retained (in principle) and a separate bank of domestic 12 volt batteries could be provided, charged via split charge relay, to give the split domestic/starter system, but balancing the charge to the battery sets might be even more difficult than usual with the SP unit and the whole system would be further complicated. A 12 volt starter for a 12 volt boat is the only sensible simple course.

Balliol.

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24V starter - 12V alternator ! 27 Apr 2020 01:38 #115571

Pete, may I suggest you figure out how your magic box works its magic. You may then learn to eventually love it for what it does! This would be my second choice. My first choice would be to change the 24V starter to 12V as your neighbour suggests. An alternator/starter shop may be able to rebuild your 24V unit as a 12V unit cheaper than buying a new starter. (Is there actually a problem with your electrical system other than your ‘hate-at-first-sight’ magic box?) I presume that the PO installed what you have as his best solution. You have the usual 12V alternator and 12V load (lights, VHF etc.). The only unusual feature is a 24V engine starter. The magic box is a simple way to make this equipment work together. Simple is good!

Here’s how the magic box works. It just contains three high-current relays and has to be connected to two 12V batteries. Normally the two batteries (A & B) are connected in parallel by the relays in the box and are kept charged by the 12V alternator as usual. When you turn the key to operate the 24V starter the magic box leaves battery A connected as before but battery B gets its connections moved. Its negative terminal gets connected to the positive terminal of battery A and its positive terminal gets connected to the starter solenoid so the two batteries are now in series to apply 24V to the starter. When you release the key the box puts the batteries back in parallel. Balliol’s diagram may help understand your rat’s nest?

Does your new old toy use one battery bank for both domestic use and engine start? Not a good idea for at least two reasons!
Trevor

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24V starter - 12V alternator ! 26 Apr 2020 14:56 #115569

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Peter Smith wrote: Pete, can you replace the starter with 24v and one 24v alternator. Then a Victron to charge both batteries.
As an alternative the actual amp hours of energy used to start an engine is not large ( say 600 amps for 1 second is 0.16 amp hours ) which is why the mobile phone sized battery's can jump start a car. I am getting around to suggesting a 24v house set up with a 12v starter, a 12v starting battery with say a 5amp 24v-12v converter feeding a 12v regulator to charge the start battery.
Ok you are relying on one alternator, but they are reliable, plus you may have a generator or solar as a backup.


The starter is already 24V. Everything else on the boat is 12V, so 24V house battery is totally out of the question! I'm not sure there is a Victron charger/inverter with 24 and 12V. On the other hand, a charger as you describe but 12V-24V DC might be a possibility, as I suggested - if there is one at a reasonable cost. Then only the starter and its battery stay at 24V.

Pete

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24V starter - 12V alternator ! 26 Apr 2020 13:01 #115568

Pete, can you replace the starter with 24v and one 24v alternator. Then a Victron to charge both batteries.
As an alternative the actual amp hours of energy used to start an engine is not large ( say 600 amps for 1 second is 0.16 amp hours ) which is why the mobile phone sized battery's can jump start a car. I am getting around to suggesting a 24v house set up with a 12v starter, a 12v starting battery with say a 5amp 24v-12v converter feeding a 12v regulator to charge the start battery.
Ok you are relying on one alternator, but they are reliable, plus you may have a generator or solar as a backup.

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24V starter - 12V alternator ! 26 Apr 2020 11:06 #115567

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"change the alternator to 24V '' is just part of a whole picture, which includes a new 12V aux battery bank. However the plan isn't complete yet.
My first aim is to remove the 'magic box' that I don't know anything about, which raises the question of how charge both battery sets when the engine is running . A second alternator looks difficult to fit in the space and the starter motor is almost inaccessible , so a DC-DC charger seems tempting. Perhaps 12-24V with the existing 12V alternator? On the other hand, that's more or less what my 'magic box' is!

The single battery, 450Ah in my case, seems to be 'normal' in smaller boats and perhaps lorries since my 'macic box' is still available, though I do plan a separate starter battery as 'good' practice.

Maybe my neighbour has the best answer and I should take enough of the boat apart to make the starter motor accessible - and just change that!

Pete

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24V starter - 12V alternator ! 25 Apr 2020 23:02 #115562

So Pete, I'm puzzled by your 'change the alternator to 24V ' comment. Are you proposing to keep your existing 12V alternator to charge your 12V domestic battery bank to feed your 12V onboard equipment and to add another 24V alternator to only feed two separate 12V batteries in series to provide the energy source for your 24V starter motor? Or do you plan to only use one 24V alternator and a 24V battery bank with a DC to DC converter to drop the 24V down to 12V for all your onboard 12V equipment? To add some more worms, I am sure you are aware it is not good practice to use the same battery bank for domestic use and engine starting, which would make the two alternators a better choice?
Trevor

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24V starter - 12V alternator ! 25 Apr 2020 16:51 #115560

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A neighbour pointed oiut thatthe 'simple' answer would be to change the starter motor to 12v, and save the cost of the second battery needed for 24V. He has a point. While chatting to Drinkwaard Motoren about the cost of a new starter, I mentioned the magic box, which they said is a standard spare part, which converts 12V to 24V for charging and (and presumably the reverse to supply equipment & lights from the battery), allowing the boat to run totally from one battery bank. Magic indeed - but it's still going out!

Pete

PS It turned out 25% cheaper to change the alternator (to24V), buy the extra battery and live with mixed voltages. There will be a new 12V domestic battery.

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24V starter - 12V alternator ! 22 Apr 2020 18:21 #115480

CUPA offer the same parallel-series battery switching relay arrangement if you want to install their more-powerful 24V CP50 bowthruster in an otherwise 12V system.
Trevor

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24V starter - 12V alternator ! 22 Apr 2020 12:44 #115462

Pete Milne wrote: I'll be changing the alternator to 24V and dumping the box - just curious!

Pete


Very wise, I'd say, KISS. Not that I'd apply the last 'S' to you!

Bob

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Bob & Bobbie Marsland
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24V starter - 12V alternator ! 22 Apr 2020 12:29 #115459

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What I have seen elsewhere is a parallel / series changeover box with changeover relays or solenoids, effectively putting the batteries in series when starting but in parallel otherwise, something like this:

www.google.com/url?sa=i&url=http%3A%2F%2Fwww.texasindustrialelectric.com%2FT_114_12_series_parallel_switch.asp&psig=AOvVaw2Abr8xZW1dQ6dpIABvKdy-&ust=1587636974076000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCKjrhuHm--gCFQAAAAAdAAAAABAM

As you say best binned!

Balliol.

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24V starter - 12V alternator ! 22 Apr 2020 11:42 #115452

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Can anyone explain how this works? On my new old!) toy the alternator is 12V and the starter 24V, with two 12V batteries. The alternator (or putting a charger on one battery) seems to charge both the batteries. There is a strange old box alongside the batteries with many wires I've not yet traced. Does anyone recognise the mystery box?
I'll be changing the alternator to 24V and dumping the box - just curious!

Pete
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