12 volt alternator

[Nige]

Hi Folks -

A very simple question here, if you have a STARTER motor that requires 24 volts on your boat engine, and have 2 - 12 volt batteries wired up to give the 24 volts required, can you also have an ordinary (65amp in this case) 12 volt alternator connected to them for charging?

 

My chief engineer is telling me its a no.........and as im selling the boat on Friday I need a quick solution !!!

 

Cheers all,

Nige

[Gibbo]

Hi Folks -

A very simple question here, if you have a STARTER motor that requires 24 volts on your boat engine, and have 2 - 12 volt batteries wired up to give the 24 volts required, can you also have an ordinary (65amp in this case) 12 volt alternator connected to them for charging?

 

My chief engineer is telling me its a no.........and as im selling the boat on Friday I need a quick solution !!!

 

Cheers all,

Nige

 

No. Best you can do is a clump of very heavy duty relays to automatically switch the batteries between series and parallel for 12 or 24 volt operation. I can't thick of a "quick solution".

 

Gibbo

[Nige]

No. Best you can do is a clump of very heavy duty relays to automatically switch the batteries between series and parallel for 12 or 24 volt operation. I can't thick of a "quick solution".

 

Gibbo

 

SO would I be right in thinking that the way to go would be a 24 volt alternator to charge the starter batteries, with some sort of split charge relay system to charge the leisure batteries at 12 volt ? Is such a system possible ?

 

Cheers,

Nige

[KenK]

SO would I be right in thinking that the way to go would be a 24 volt alternator to charge the starter batteries, with some sort of split charge relay system to charge the leisure batteries at 12 volt ? Is such a system possible ?

 

Cheers,

Nige

 

See Gibbo's reply it's six of one half a dozen of the other. I would have thought simplest would be a 12 V starter motor and battery. If you're selling it how did it work before?

 

Ken

[Tony Brooks]

No. Best you can do is a clump of very heavy duty relays to automatically switch the batteries between series and parallel for 12 or 24 volt operation. I can't thick of a "quick solution".

 

Gibbo

 

 

And I understand such things were standard on certain Merc Vans - perhaps try a scrappy.

 

Tony Brooks

[KenK]

And I understand such things were standard on certain Merc Vans - perhaps try a scrappy.

 

Tony Brooks

Don't know which ones, we have used Mercs for ever, currently Sprinters and Vitos they all use standard 12 V. We even have two with lifts, side and tail and they have hydraulic pumps driven from the engine.

 

Ken

[Big Steve]

I've a similar problem with a 24v Webasto heater. After lots of thought I've decided to use a 3 pole changeover switch, easily obtainable, inexpensive, allows 24v for when needed, when not needed charges both batteries via 12v alternator. if you're struggling with the concept E mail me and I'll send a diagram.

 

On second thoughts, it won't be inexpensive in your case because it will have to be rated at, at least, 400A and 400A switches, or relays aren't cheap. Another way would be to have a extra battery dedicated to starting and use a 12v-24v inverter to charge the pair, or a second alternator just for the extra battery.

Edited September 12, 2007 by Big Steve

[Sir Nibble]

The correct component is available. I just can't remember which catalogue to look in. There was another member with the same problem set himself up with one a while ago. Give me a while and I will get back with a part number.

[Sir Nibble]

That was probably quick enough for "automerge", so don't blame me if this post looks weird.

Contact your local branch of lucas service, you want CARGO part number 180290. This is a pukka bit of kit designed for exactly what you want to do.

[RobinJ]

A very simple question here, if you have a STARTER motor that requires 24 volts on your boat engine, and have 2 - 12 volt batteries wired up to give the 24 volts required, can you also have an ordinary (65amp in this case) 12 volt alternator connected to them for charging?

Yes.

Many of the diesel engined Nauticii used a 24V starter with a 12V system. You need to wire an additional start solenoid which is cascaded off the original and connects the -ve of the first to the +ve of the second. If done correctly it interlocks so the batteries cannot be shorted if anything goes wrong. The trick is to know which -ve to use (as there is one at 0V and one at 12V during starting).

I may not have a copy of the circuit anymore, but I will have a look.

 

P.s. The reason it is done is normally for extra torgue.

Edited September 13, 2007 by RobinJ

[smileypete]

Hi Folks -

A very simple question here, if you have a STARTER motor that requires 24 volts on your boat engine, and have 2 - 12 volt batteries wired up to give the 24 volts required, can you also have an ordinary (65amp in this case) 12 volt alternator connected to them for charging?

 

My chief engineer is telling me its a no.........and as im selling the boat on Friday I need a quick solution !!!

 

Cheers all,

Nige

 

Hi,

 

I'd see if the starter is available in 12v.

 

If so a place that reconditions starters might also be able to rewind it for 12v if the brushes etc are the same.

 

cheers,

Pete.

[gary4lw]

That was probably quick enough for "automerge", so don't blame me if this post looks weird.

Contact your local branch of lucas service, you want CARGO part number 180290. This is a pukka bit of kit designed for exactly what you want to do.

Twas me you helped, solid bit of kit too cant tell you what i paid for i would have to kill you!!!!!!!!

[Big Steve]

That was probably quick enough for "automerge", so don't blame me if this post looks weird.

Contact your local branch of lucas service, you want CARGO part number 180290. This is a pukka bit of kit designed for exactly what you want to do.

 

That might be just the thing for my Webasto problem. Any one got a cct diagram so I can see what it does? Lucas site no help.

[Sir Nibble]

Twas me you helped, solid bit of kit too cant tell you what i paid for i would have to kill you!!!!!!!!

It is solid gear isn't it. Cargo are a Danish company who supply a phenomenal range of parts for alternators and starters, as well as complete units, lamps, switches, relays, cable and whatever, you name it! As for what you paid, price to us is £62, and if it were up to me I would be sending stuff out to forum members at cost, but I am under the iron heel of Satan. That's why I always refer people to lucas for these bits.

That might be just the thing for my Webasto problem

'Fraid not, the part is not continuously rated, and would cause dreadfull battery imbalance problems.

[Nige]

See Gibbo's reply it's six of one half a dozen of the other. I would have thought simplest would be a 12 V starter motor and battery. If you're selling it how did it work before?

 

Ken

 

The engine in question is a Mercedes 636 and the old alternator that was on I believe was a 24 volt one - no way to tell as its now deceased and had absolutely no markings on it. Thats whats caused the problem - it died and I've had to replace it. I was under the impression - wrongly as it turned out - that a 12 volt alternator was ok to charge a 24 volt bank.

 

I dont think this engine would cope with a 12 volt starter, not sure. And as im selling the boat I dont really want to get involved to that level.

I was hoping there could be a simpler solution that would allow the batts to be charged without major work involved

Cheers,

Nige

[Sir Nibble]

Fastest, simplest solution is to have the old alternator rebuilt I'd have thought.

[DHutch]

Or get another 24v one.

- If i had any idea where the first alternetor off emilyanne went i would offer it to you, wouold do you fine as it was only replaced becuase we couldnt spin it fast enough.

 

 

 

Daniel.

[RobinJ]

I may not have a copy of the circuit anymore, but I will have a look.

Sorry Nige, looks like everything was passed on when I sold the boat!