Hi, I didn’t know what forum to ask this question and this one seems to have very knowledgeable people so I came here lol.

How do I make an alternator put out 56v in an easy way? Let me start by saying I’m starting with a 48v alternator that was also shipped in a 56v version. Leece Neville 4417jb is the 48v and 4420jb is the 56v. The manufacturer says they are the same and can be interconverted by a regulator swap. Which would be simple, if they weren’t discontinued.

Could I use my regulator with some resistor or something? Maybe the 14v version regulator modified to sense 1/4 of the inputs therefore supplying 56v while only “seeing” 14v?

My goal is to charge a 48v battery bank and I obviously would have a hard time doing that on 48v. It’s a 95 amp alternator so boosting 5kw would probably smoke any boost converter I could come up with.

Thank you so much for your help.

Also, I’ve looked into aftermarket regulators but have come up short unfortunately.

 

Alternators use a Excited Field winding to generate the voltage, it's just a matter of regulating the DC voltage applied to the Field, using a comparator.

 

So raise the “ignition” voltage while measuring the output voltage until I get the desired output?

It crossed my mind but I wasn’t confident that I wouldn’t blow the regulator.

Thank you, I appreciate the advice.

 

I have done it with a LM317 for DC generators up to 230vdc.
Max.

 

I’m confused now, do I strengthen the field voltage or lower it? The lm317 seems to be a voltage limiter so wouldn’t that be counter productive?

 

Is there a specific off the shelf item that I can buy? I understand I’ll have to set it manually using a voltmeter on the alternator output.

 

Sorry it should be LM311 comparitor.
One input uses a pot to set the output value, the other monitors the alternator rectified DC, for an alternator it requires a DC supply initially, battery bank etc similar to the automotive alternator.
Max.

 

This alternator outputs 48v but the field is ran off of 12v so I’ll have to have that second voltage source regardless.

 

So the present set up uses a different supply for the field than the generated output?
Max.

 

Yes, that’s how the alternator is designed. It expects a 12v source to excite the field.

https://smithcoelectric.com/products/r240103745s-new-oe-electronic-regulator-for-leece-neville-48v

 

Have you checked internally if there is any adjustments etc in order to set the present generator output, if so try tweeking it !
Max.

 

I don’t believe there is, it’s labeled as “non adjustable”. That’s why I was hoping to mess with the input voltage, if it’s a 4 to 1 ratio then it should be easy to just bump up the field, but I’m not confident that I won’t blow the regulator that I can’t get a replacement for.

Right now it’s a desk ornament until I get the engine I want to mount it to, which will be next payday. There’s some good deals on yanmar 3cyl diesels on Craigslist locally at the moment.

 

Obviously that one will be monitoring the output voltage from the alternator itself.
Is it possible to reverse engineer it? is it all surface mount electronics?
The LM311 version is not that hard to build, if only for a stand by etc.
Max.

 

Sealed in epoxy resin unfortunately.

I’m not even 100% sure what “48v” and “56v” mean in this context. Is it a 48v nominal alternator that will output 56v and charge a 48v battery or is it a 48v actual output? From what I understand 56v nominal battery systems do exist but are quite rare.

I guess I’m getting ahead of myself and need to get the thing running so I can check it with a voltmeter. I was going to take it to the auto parts store today to have them put it on their machine and they can get it excited but the output is too high for their machine and of course when I go to work to grab my voltmeter someone borrowed it without ask

 

56v peak charge sounds about right to charge a 48vdc battery, obviously 48v would not do it.
Max.

 

Well, I got extremely lucky and after about 20 emails I have the very last factory 56v regulator from prestolite.

Help me understand, since the alternator is a constant voltage device and not a constant current I should be just fine charging a lead acid or lifepo4 battery from a 56v source right? Because as the battery fills it will draw less and less current due to the battery current becoming closer and closer to the charging voltage. Correct? Or am I forgetting something? I’m no expert.

My preference is lifepo4 but due to cost lead acid seems like it will be the initial battery bank only to be upgraded later. (And probably in parallel with the lifepo4 in the charging circuit separated with a relay only connecting during charging).

 

The alternative is to run an inverter directly from the alternator (it’s a 100% duty cycle alternator that comes on a golf course mower that runs 3 electric motors with no battery) and use that inverted power as “shore power” to another inverter/charger which would charge the batteries.

 

Just for the record you're not alone on that converting a 48 to 56 V
And I firmly believe I founD The last voltage regulator on the planet
Took a month of research but I found one in Quebec Canada.
Now the question I have for you is your alternator running hot?
Does it kick up to 56 volts real fast?
The reason I ask because I've went into further investigation and the rotors are a different part number
And they seem to be interchangeable with specific 12 V alternator's and the larger rotor number that fits the 56 bolt seems to be putting out 165 amps in the 12v section and the rotor that comes with a 48 V inner changes with a 12 V and it only puts out 105 A in a 12 V alternator so I am guessing that the rotor is built heavier I don't know this yet because I haven't acquired a 150 on eBay 200 on Amazon believe it or not. Of all places
No matter what I'm sure you know it's definitely cheaper than trying to buy a 56 V alternator out right.
Anyway I stumbled across your posting while trying to research and find the actual capacitor to work the 56 V alternator which is a different part number as well

 

I have the diesel motor I planned on using, a 1L yanmar. I have the alternator but in regards to your question it was 48v to begin with so for me the only part that was different was the regulator.

Also since I changed jobs to being a trucker I gave up my apartment until I find a house and it’s all sitting in a storage unit. I tried to run it once but it was a waste of time since at that time I didn’t have a 12v alternator or a spare battery so powering the coil was a problem. Sorry I couldn’t be more helpful

 

Well we are learning all these idiosyncrasies on that 48 V alternator if and when you ever do get to use it you will find it runs hot, and when all our parts come in I will update you on how it works.
Not that we need it but if you should ever wanna get rid of yours let me know
But as I said before if you pull up lease neville technical manual on the 48/56v alternator there is definitely three parts that have have different part numbers