24v to 12v series to parallel switching.

[179580]

I would think that you may be barking up the wrong tree. I have experience of 2 vessels fitted with this engine, both working on a standard 12 volt system. Both , even in cold weather, were on the button. Saying that both were fitted with a diesel fed thermostart in the manifold. Was this 12/24 system fitted from new? Stephenson Marine, Dartmouth are the go to for the Sea Panther.

 

[VicS]

Yes you are right there

When I was designing my current boat I selected a 12Vdc bow thruster. Yes this ment bigger cables but as I was building it was easy to fit big bus bars.

I picked up an above deck andersen winch motor that is 24dc so I will need to look at how to drive it but that some time ahead. One reason I looked at the post.

As Vic pointed out its rated at 100 A continuous so it would not drive my Vetus bow thruster 600 Amp max but it could drive a 24Vdc starter motor as a starter motor is only intermittent operation

Yes but the trouble is that it is a 12 volt starter motor being run from a 24 volt supply ! The current will be much higher than it would be if run off 12 volts or for that matter if it was 24 volt motor.
My understanding is that without preheating a normal 12 volts system did not crank the engine fast enough to get it stated hence the 12 volt motor being run at 24 volts.

 

[VicS]

I would think that you may be barking up the wrong tree. I have experience of 2 vessels fitted with this engine, both working on a standard 12 volt system. Both , even in cold weather, were on the button. Saying that both were fitted with a diesel fed thermostart in the manifold. Was this 12/24 system fitted from new? Stephenson Marine, Dartmouth are the go to for the Sea Panther.

ITYWF that early versions were fitted with this 12/24 volt system. Later versions were fitted with the thermostarter and a normal 12 volt system.
I,m sure the OP knows what system he has

 

[179580]

ITYWF that early versions were fitted with this 12/24 volt system. Later versions were fitted with the thermostarter and a normal 12 volt system.
I,m sure the OP knows what system he has

I am sure he knows what he has as well. I was questioning if these engines were so fitted as the 2 versions I experienced were not. May be a more prudent system to fit the thermo.

 

[PaulRainbow]

But not adequately rated to use for engine starting

You're mistaken. It's used to power bow thrusters up to 11kw.

 

[rogerthebodger]

You're mistaken. It's used to power bow thrusters up to 11kw.

A 11kw bow thruster would draw just under 500 Amps at 24Vdc and the one I posted has a continuous current rating of 100 Amps with a 20% intermittent rating of 150 Amps.

I would not like to use one of these on my 699 Amp at 12Vdc of 300 Amp at 24 Vdc.

Don't know about the starter motor in question and what start and run current a 12vdc motor would draw when powered with 24 Vdc.

 

[PaulRainbow]

A 11kw bow thruster would draw just under 500 Amps at 24Vdc and the one I posted has a continuous current rating of 100 Amps with a 20% intermittent rating of 150 Amps.

I would not like to use one of these on my 699 Amp at 12Vdc of 300 Amp at 24 Vdc.

Don't know about the starter motor in question and what start and run current a 12vdc motor would draw when powered with 24 Vdc.

You are also mistaken, the 24v-12v series/parallel switch has a continuos rating of 400a or 1000a for 60 seconds.

It is designed to power 11kw bow thrusters, like i said in my last post.

 

[rogerthebodger]

You are also mistaken, the 24v-12v series/parallel switch has a continuos rating of 400a or 1000a for 60 seconds.

It is designed to power 11kw bow thrusters, like i said in my last post.

OK the one I posted says 100 A continuous so where does it say continuou 400a or 1000a for 60 seconds.

Do you have a link for the one you are looking at.

Not disagreeing just confused.

Vetus Series parallel switch for 24 volt thruster with 12 vo (Vetus BPSPE)

" These contacts have a continuous duty rating of 100 Amps, and an intermittent 20% rating of 150 Amps. "

This is the bit confused me

 

[PaulRainbow]

OK the one I posted says 100 A continuous so where does it say continuou 400a or 1000a for 60 seconds.

Do you have a link for the one you are looking at.

Not disagreeing just confused.

Vetus Series parallel switch for 24 volt thruster with 12 vo (Vetus BPSPE)

" These contacts have a continuous duty rating of 100 Amps, and an intermittent 20% rating of 150 Amps. "

This is the bit confused me

Vic has led you astray by telling you it won't start an engine and it's only rated at 100a

The very first line on the Vetus page states "The 160 kgf and 220 kgf bow thrusters are only available with a 24 Volt DC electric motor. " The 220 kgf thruster is 11kw

It then goes on to say "When the batteries installed for the bow thruster are also used for other 12 Volt consumers, it should be remembered that the current is supplied via the charging contacts of the series/ parallel switch.

These contacts have a continuous duty rating of 100 Amps, and an intermittent 20% rating of 150 Amps. As a consequence, never use these batteries as starter "

The series connection, for powering the thruster, is rated at 400a continuous, but when it reverts to parallel connection the batteries are connected through a lower rated circuit, 100a continuous. The relay is obviously intended to power a 24v thruster from two 12v batteries, which could easily be done by just wiring them in series, but on an otherwise 12v vessel there wouldn't be a way to charge the batteries. With the Vetus switch, one of the batteries is connected to a 12v charging source and when in parallel mode the switch charges the other battery. The reason for not connecting a windlass or an engine to one of the batteries is that it would try and draw more current from the other battery than the parallel/charging circuit could carry.

It's an expensive solution to running a 24v thruster, IMO. Personally, i'd just wire them in series and fit a 12v to 24v charger, cost about £250

 

[oldmanofthehills]

already covered.

 

[VicS]

OK the one I posted says 100 A continuous so where does it say continuou 400a or 1000a for 60 seconds.

Do you have a link for the one you are looking at.

Not disagreeing just confused.

Vetus Series parallel switch for 24 volt thruster with 12 vo (Vetus BPSPE)

" These contacts have a continuous duty rating of 100 Amps, and an intermittent 20% rating of 150 Amps. "

This is the bit confused me

I misunderstood this and as a result have probably confused you.

The 100 amp rating refers to the auxiliary contacts which only carry the charging current ... obviously 100 amp rating for these is more than adequate for the Sea Panther

The main contacts carry the load current ( Bow thruster or in the case of the Sea Panther the starter motor current)
The bow thrusters mentioned in the link for which this unit is required draw 450 and 720 amps respectively . Clearly it'll handle the Sea panther starter current easily and far from being underated as I suggested .

The warning is against using the dedicated bow thruster batteries for large 12 volt loads, such as a windlass, because that could result in an excessively large current being drawn via the auxiliary contacts .

Possible solutions if the OPs unit is defective include

• Replace with the same if available
• A low cost work around with a relay
• A permanent 24 volt battery charged by a battery to battery charger
• Investigate the possibility of an all 12 volt system and a "Thermostarter"

 

[rogerthebodger]

OK Thanks Paul and Vic

Confusion resolved.

 

[PaulRainbow]

I misunderstood this and as a result have probably confused you.

The 100 amp rating refers to the auxiliary contacts which only carry the charging current ... obviously 100 amp rating for these is more than adequate for the Sea Panther

The main contacts carry the load current ( Bow thruster or in the case of the Sea Panther the starter motor current)
The bow thrusters mentioned in the link for which this unit is required draw 450 and 720 amps respectively . Clearly it'll handle the Sea panther starter current easily and far from being underated as I suggested .

The warning is against using the dedicated bow thruster batteries for large 12 volt loads, such as a windlass, because that could result in an excessively large current being drawn via the auxiliary contacts .

What i said in post #29, glad you read and understood it

 

[ncritchley]

Good evening everyone, its the OP here, and I'd just like to update you all on progress. Despite my various suspicions regarding the proper functioning of the switch, or the state of my batteries, the solution was indeed that proposed by VicS, and perhaps others. In fact I'd failed to ground the number 5 terminal (I'd like to say because the diagram wasn't clear, but really it's down to my own poor understanding). So all is now working perfectly, and I'd just like to thank you all again for the extraordinarily helpful comments.
I've followed this conversation with interest, and I realise that I should really have provided a little more information at the outset. My engine is indeed one of the earlier models, and the factory manual clearly shows a 24v configuration, witha 24v alternator and solenoid but a 12v starter motor. I inquired into this in some depth a few years ago, talking to both Stephenson Marine and Sheridan's. It appeared that the gear ring ratio on the flywheel of these early models was changed to allow for this unusual method of starting. Even with this setup, the engine wasn't always keen to start, until I fitted a tractor-style glowplug as a preheater. It now fires up within a few seconds. Surprisingly, in nearly a decade, I've only had one starter motor burn out, and at £50ish new from a factor, I just keep a spare on board.
But it's been a pain trying to get the whole 24v to 12v step down arrangment to work satisfactorily for the domestic circuits, which is why I wanted to install a series/parallel switch. Also because the old 24v alternator is on its last legs, and I had a shiny new 12v one in the shed!
Happy to answer any questions. Best wishes, Neil

 

[PaulRainbow]

Good evening everyone, its the OP here, and I'd just like to update you all on progress. Despite my various suspicions regarding the proper functioning of the switch, or the state of my batteries, the solution was indeed that proposed by VicS, and perhaps others. In fact I'd failed to ground the number 5 terminal (I'd like to say because the diagram wasn't clear, but really it's down to my own poor understanding). So all is now working perfectly, and I'd just like to thank you all again for the extraordinarily helpful comments.
I've followed this conversation with interest, and I realise that I should really have provided a little more information at the outset. My engine is indeed one of the earlier models, and the factory manual clearly shows a 24v configuration, witha 24v alternator and solenoid but a 12v starter motor. I inquired into this in some depth a few years ago, talking to both Stephenson Marine and Sheridan's. It appeared that the gear ring ratio on the flywheel of these early models was changed to allow for this unusual method of starting. Even with this setup, the engine wasn't always keen to start, until I fitted a tractor-style glowplug as a preheater. It now fires up within a few seconds. Surprisingly, in nearly a decade, I've only had one starter motor burn out, and at £50ish new from a factor, I just keep a spare on board.
But it's been a pain trying to get the whole 24v to 12v step down arrangment to work satisfactorily for the domestic circuits, which is why I wanted to install a series/parallel switch. Also because the old 24v alternator is on its last legs, and I had a shiny new 12v one in the shed!
Happy to answer any questions. Best wishes, Neil

So, you have a 24v alternator and solenoid, but a 12v starter motor that you run at 24v ? If that's true, i don't understand why you are fitting the series/parallel switch. All you needed to do was to wire the batteries in series to give 24v for starting and to be charged by the 24v alternator, then fit a 24v to 12v DC-DC converter to run the 12v systems.

So how is the 24v alternator connected ?

 

[ncritchley]

So, you have a 24v alternator and solenoid, but a 12v starter motor that you run at 24v ? If that's true, i don't understand why you are fitting the series/parallel switch. All you needed to do was to wire the batteries in series to give 24v for starting and to be charged by the 24v alternator, then fit a 24v to 12v DC-DC converter to run the 12v systems.

So how is the 24v alternator connected ?

What you suggest has in fact been the layout for the last few years. But the parallel switch idea came about for several reasons:

- My 24v alternator was failing and a replacement was expensive, while I had a brand new 12v one already in the shed
- I wanted to have 2 separate battery banks (each 2 x 12v), one kept exclusively for starting purposes
- The stepdown converter I have doesn't do a very good job, and I was loathe to spend unnecessarily, when I had all the components already available (including the series/parallel switch) to carry out the conversion.

I may have made things unecessarily complicated, but as you'll have gathered, marine electrics really aren't my strength.

I realise it leaves me still with 24v on a 12v starter, but they do seem to be remarkably resilient!

Anyway, all working beautifully now, thanks to you guys.