can you make a 12v alternator into a 24v alternator

[SVSAVANNAH]

Must be possible, I have a free balmar 95-SERIES (9504-965). it is 12v my boat is 24v....


Can you make a 12v alternator into a 24v alternator?




cheers

[KeelMe]

Certainly.

[SVSAVANNAH]

I should have been more specific in my question.....




HOW

[Dsanduril]

Short answer, it's probably cheaper and certainly easier to buy a 24V alternator. There are couple of threads on this subject already.

On the technical side, the field winding of the 12V model has a resistance/impedance of about 2.4 Ohm. That results in a field current of 6A at 14.4V. If you use it as is in a 24V system you'll get 12A at 28.8V through the same winding, resulting in 4x heat generation in the field and death of the alternator. -> Done properly the field has to be rewound for the change in voltage (and a few other steps).

If it was your only choice, in the boonies, it could be done. Most competent shops could rewind, but if you're anywhere you can just buy a 24V bus/ambulance alternator...

[SVSAVANNAH]

it is my only choice, I'm in the boonies..... so I need to rewind the armature?


How do I calculate length and size of winding? what else do I need to do?

[KeelMe]

Take it to an alternator shop.

[sailormed]

Originally Posted by SVSAVANNAH

it is my only choice, I'm in the boonies..... so I need to rewind the armature?

Being in Indonesia is “in the boonies....”?

[SVSAVANNAH]

Regulator not sorted yet .... are you saying just hook it up to a 24v regulator and it will just work????????

[KeelMe]

614 = 14v
624 = 24v

[SVSAVANNAH]

are you saying just hook it up to a 24v regulator and it will just work????????

[rom]

Originally Posted by Dsanduril

Short answer, it's probably cheaper and certainly easier to buy a 24V alternator. There are couple of threads on this subject already.

On the technical side, the field winding of the 12V model has a resistance/impedance of about 2.4 Ohm. That results in a field current of 6A at 14.4V. If you use it as is in a 24V system you'll get 12A at 28.8V through the same winding, resulting in 4x heat generation in the field and death of the alternator. -> Done properly the field has to be rewound for the change in voltage (and a few other steps).

If it was your only choice, in the boonies, it could be done. Most competent shops could rewind, but if you're anywhere you can just buy a 24V bus/ambulance alternator...

If it has an external field input (as opposed to self excited) you may feed it 12V and connect its output to a 24V battery. It may not be able to provide enough voltage at low speed though. If you know which math applies here it could be interesting. The voltage sense of the VR should then be connected to one of the 12V batteries making the 24V battery, if it is built this way... Interesting science project but knowing a 28SI 24V 110A is about 250USD I would not hesitate much.

[a64pilot]

Never done it, but gut says it won’t make 24V for long, if at all.

[SVSAVANNAH]

Let me restate my original question:


What is the internal difference between an unregulated 24v and a 12v Alternator? And can one be modified from one voltage to the other?

[markcouz]

24v alternator of same power (so half the amps) will have double the number of windings of a thinner diameter.

[markcouz]

You could get 24v from a 12v alternator by fiddling with the voltage on the sense wire, you would need to run the alternator at much higher rpm (because you have half the required windings) and limit the amps to 50% or less of the 12v rating, otherwise you will burn out the alternator.

I have done this on a vehicle to raise output by 0.5v, but doubling the output voltage sounds like a horrible idea to me, but each person must determine their own level of acceptance.