Convert alternator to 56v?

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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.
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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.
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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?
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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.
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
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.
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
This alternator outputs 48v but the field is ran off of 12v so I’ll have to have that second voltage source regardless.
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
So the present set up uses a different supply for the field than the generated output?
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
Have you checked internally if there is any adjustments etc in order to set the present generator output, if so try tweeking it !
Max.
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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.
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
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.
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
56v peak charge sounds about right to charge a 48vdc battery, obviously 48v would not do it.
Max.
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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).
 

Thread Starter

Iqinsanity

Joined Oct 6, 2019
10
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.
 
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