55 amp alternator to an 80 challenge!!!

[glcalahan]

I am rebuilding a Yanmar 2GM20F that comes stock with a 55 amp alt. Question is: would it be possible to re wind the armature to increase amperage for stock 55 amp to an 80 amp alternator? It is my understanding the case is about the same size OR can the amp be increased at all by rewinding???

The amp/alt challenge!!!

[john61ct]

Plenty of custom alt shops can do something like that.

But in reality, the small case makes it likely that putting out high amps will heat things up, and most regulators just cut voltage when that happens, not current.

Maybe you can adapt it to a VR like Balmar MC-614 and get better control.

But really for true continuous HO, moving up to a big large-case unit designed for that is much better.

But but, depending on your bank chemistry you may only shorten the time it takes from 50% to Full by say 30 minutes, maybe 6 hours down to 5:30

[glcalahan]

Perhaps it's not worth worrying about. I am installing 3 group 31 AGMs.

[Compass790]

Dont know whereabouts in the world you are but sometimes you can get good used 80amp alternators cheap as people are always upsizing. Agree with John61 about upping yrs.

[a64pilot]

Arrg,
When you reduce output voltage, you reduce output current, or said another way, reduce current and voltage will drop too.
Think about it, your XX amp alternator is trying to drive bank voltage up to absorption voltage, but cannot, because it’s current limited at XX amps, and it would take XXX amps to get to absorption, so it holds max output until it either burns up or its field current is reduced because the thermal sensor has hit the temp it cuts back at, reducing field current reduces output current and therefore voltage.

Once the bank is fully charged, the field current is adjusted so that the output voltage stays at set point, this is usually below the max output and or temp limit so it happily maintains voltage set point.


Now what is really, really important if you want to get the most out of your stock 55 amp alternator is not rewiring it to get 80 amps, cause it will still have the dumb or rather smart stock internal regulator.
It’s dumb in that it won’t charge batteries very well, but rather smart cause it protects the alternator so well they last for years, and years.

To charge your batteries well you need a smart external three stage regulator with an alternator temp sensor and a bank temp sensor is nice to have too.
The Balmlar 614 seems to be an excellent piece of kit, ought to be for the price it costs.
So have your alt modified for external regulation, and get a good external regulator, there are many that are decent and a whole lot less $$$ than the Balmar 614.

[rom]

Originally Posted by glcalahan

I am rebuilding a Yanmar 2GM20F that comes stock with a 55 amp alt. Question is: would it be possible to re wind the armature to increase amperage for stock 55 amp to an 80 amp alternator? It is my understanding the case is about the same size OR can the amp be increased at all by rewinding???

The amp/alt challenge!!!

Interesting project ! a few thoughts:
- my hitachis (2 in a cat) 80A actually deliver about 30A continuous, that is at about 2000 RPM but I don't think it changes much at different revs.
- I wouldn't be surprise you get about the same output with the stock 55A model since I believe the 55A is the same case as the 80A. maybe it's only a voltage regulator difference between the two ?

If you are up to that kind of modification you may as well consider using an external bridge rectifier (110 USD at alternatorparts.com). Removing that much heat from the alt should allow for (much?) higher continuous ouput.

You would also need an external regulator, maybe you don't need anything smart and any reg at 30 USD will do fine for you. A potentiometer inline the field would allow you to manually decrease the alternator ouput in case it would still get too hot.

This is something you like to do, so please do it before and let me know how it works

[glcalahan]

Thanks! I am not sure I am able to commit the time as I am doing a complete rebuilt stem to stern and rebuilding the Yanmar. I plan to have take the alt to have it torn down and rebuilt too and wondered if this could be done. I have my hands full. My limited electrical knowledge didn't know it was so limited! Thanks!!

[glcalahan]

Rebuild of a 1972 Pearson 33 that is.......

[a64pilot]

In truth if money and time is an issue and you have a good shorepower Charger.
The little Honda EU2000i is tough to beat for its price, just barely under a grand, Mayberry’s has it on sale right now for $965 delivered.
Price a good high output alternator and of course say a Balmar 614 or a kit including both, then if you are like most of us, you’ll spend more time at anchor than anything and maybe you don’t want to run your freshly rebuilt Yanmar to charge.
Assuming you don’t already have generator of course.
Of course Solar is very nice to have too, it will do the majority of charging on a good day.
Of the three in my opinion the alternator is the least important charge source.

[glcalahan]

Yes, I do agree. I also do own a Honda 2000i, no panals yet but I do have a new....yet to be installed ProMariner charger for the 3 new group 31 AGM batteries. I will be looking into solar panels but currently the Yanmar is in pieces as of yesterday and have to get engine compartment ready for paint and painting, clean and paint engine parts, get the engine reassembled, put the new shaft, packing gland, cutless bearing and prop......ugh! Just never ends till you are done! Well....that won't happen!!! Thanks all! Some really great ideas!

[pcmm]

You can pick up an 80 or 100amp hitatchi replacment alternator for around $100, find yourself a Pro-RegD external alternator and their instructions actually show you how to modify the alternator for external regulation. Its really simple in reality, just need to solder a couple of wires onto the brushes (you don't even need to remove the internal regulator, its that easy!) lead them out of the case and connect it up to the Pro-regD. That's the hardest part. follow the instructions and you'll have an 80amp externally regulated alt with internal reguolator backup for probably less than $200 if you keep an eye out on ebay and the like for a Pro-RegD

That's what I did. all the Original yanmar connections still fit too!

[glcalahan]

Great input thanks!

[Dave Lochner]

If you are investing in AGM batteries it is important to charge them correctly and frequently. These articles will help you sort it out.

https://marinehowto.com/automotive-a...cle-batteries/

https://marinehowto.com/how-fast-can...ry-be-charged/

and others on the site. Compass Marine also sells externally regulated 80A and 90A alternators.

[hellosailor]

Usually when 55-65-70-80 amp alternator options exist and they all look alike, the maufacturer actually uses a slightly longer case for each one. So the width is the same, the installation is the same, but each step up makes a little more alternator overhang the rear mount. And the coil assembly, etc. is also longer, using the extra length to carry more wire in both the coil and frame. Side by side, they won't look quite the same anymore.

[glcalahan]

Thank you!!!