Fitting an external regulator to alternator

Ed Schenck · Jan 22, 2012

Really hard to do without the wiring schematic from the regulator manufacturer. You should be able to find one online as an example. Also depends upon the alternator, whether it requires an exciter voltage. Then modifying the alternator. I tried to find someone to modify my 80 amp Hitachi, could not. Sold it and bought a Balmar.

Bill Roosa · Jan 22, 2012

How much do you know about alternators?
The primer goes like this; there are 2 coils of wire, the stator which does not move and produces all the electricity in AC form and the rotor which spins with the alternator and is controlled by the regulator to increase or decrease the output of the stator. More rotor current means more stator output for a given rotor RPM. The rotor gets its power through the two slip rings and brushes. An internal regulator connects to one of these brushes and the other brush connects to ground. The regulator MAY also have the diode pack in it which changes the stator AC current to DC for use on the boat. There is also a connection from the regulator to the stator winding so the regulator can "see" the stator output. It uses this "voltage sense" wire to get feed back on how much to increase/decrease the rotor power so the stator output is where it should be.
If you want to convert to external you first have to determine where the diode pack is. If it is separate from the internal regulator it is pretty straight forward wiring. If it is internal to the regulator then you are going to have some challenges.
An external regulator only has two wires that connect to the alternator. The rotor power positive and the voltage sense wire. The rotor ground can be internal to any part of the alternator case. The voltage sense wire SHOULD go on the batteries (check the manual with the external regulator) The rotor power positive would normally just plug into the two wire plug on the alternator case used for that purpose. Since you have an internal regulator there probably is no two wire plug and you will have to drill a hole or route the wire through one of the cooling air slots. and of course take out the internal regulator.
But you have to make sure the diodes work once the internal regulator is out.

Also note the small hole in each rotor brush holder housing. These holes line up with a hole in the alternator case. if you compress the brush into the housing and run a paperclip through the hole the brushes stay in place and you can get the rotor back in the alternator case with very little effort. Then just pull the paperclip once everything is back in place and the springs will cause the brushes to contact the slip rings. Failure to know this results in a trip to the local electrical shop who does understand how to do this.

Bill Roosa · Jan 22, 2012

The diodes will be connected to the stator wires directly or to the alternator case. There are 6 of them and they all alike. If you have a negative ground wire on the back of the alternator the diodes connect to the stator or a buss the connects to the negative ground wire. All they are is one way valves that take the 3 stator coils (6 ends) output and direct them all in the same electrical direction (+ and -). All the stator coils are interwoven so it will only look like one coil of wire.
At this point a picture of the alternator innards or the model number and shop manual would be very handy.

Stu Jackson · Jan 22, 2012

Ken, let's keep it simple. Maine Sail has addressed many of these issues, in his Musings in Featured Contributors.

1. ...so that I get better charging when on engine... It isn't necessarily true. http://forums.catalina.sailboatowners.com/showthread.php?t=125392

2. Have your daily use loads changed? If not, what makes you think you need more charging?

3. What size is your stock alternator, and your house bank size and your daily load? In many cases, a larger house bank can suffice in lieu of changing the alternator and regulator.

4. If you do the swap, consider also Maine Sail's admonitions to avoid expensive alternators, since Leece Neville makes Balmars for Balmar. http://forums.catalina.sailboatowners.com/showthread.php?t=106489

5. Do you have a battery monitor?

Maine Sail · Jan 22, 2012

A reputable alternator REPAIR shop should be easily able to convert your Hitachi alt to external regulation. I believe a good shop may still be able to locate an internal regulator "dummy" for the Hitachi. That "dummy" regulator and allows you to tap directly into the alternator field supply but does not "internally regulate".

The problem with DIY'ing this is that the regulator and brush assembly on a Hitachi is all one unit. You need to do some surgery on the regulator, cut some soldered pieces and then tap directly into the field brush if your shop can't find the dummy reg/brush holder.

Ed Schenck · Jan 22, 2012

Yep, that's what you told me way back when Maine Sail. After calling around I found a shop, "sure no problem". They had worked on my starter once. Then they saw the alternator and said they wouldn't try it. So my point is that we need the name of some shops that can and will.

Maine Sail · Jan 22, 2012

Ed Schenck said:
Yep, that's what you told me way back when Maine Sail. After calling around I found a shop, "sure no problem". They had worked on my starter once. Then they saw the alternator and said they wouldn't try it. So my point is that we need the name of some shops that can and will.

My guy up here in Maine can do it... I will ask him about the dummy regs to see if he can still get them.

Ralph Johnstone · Jan 22, 2012

Had a Shop ..........................

..................... up here make a small rewiring change (according to him) on my original Hitachi 128170-77010, S114-305, 7Y5 alternator for $48.00. I have done a business with him before and he seems like a nice guy and just maybe wanted to keep me coming back. It was now set up for external regulation.

I chose the Balmar ARS-5 regulator because it seemed complex and a neat toy to play with. I have found it suits my needs perfectly as it puts out far more amps at 14.7V (bulk) than the previous regulator at 14.2V (bulk). That 14.7V would be just too much on a constant regulator for 8 hrs of motoring. The old regulator just never got the batteries over 80% regardless of how much motoring we did. This is according to the Link 10 Battery monitor. According to the monitor we are now able to hit 100% given sufficient motoring time.

So far the external regulator has behaved perfectly. The one problem I am still working on is cooling the small shoe box the 2GM20F sits in as it is causing the alternator to operate at 80 deg. C. now that it has to work for a living. Actually, I have set the Alt. Temp. Limit on the Balmar to 80 deg. C. and at that temperature, the charging voltage starts to cut back. This increases the time to a full charge but certainly much better than the previous regulator.

Stu Jackson · Jan 22, 2012

You can also use Small Engine Mode to drop the output to 50% until you have some charge back in the house bank. rtfm.

Ralph Johnstone · Jan 22, 2012

I have the same setup as you do Ken and no room for another house battery. That is why it's important to me to get as much charge back into those batteries as fast as possible.

Maine Sail · Jan 23, 2012

Ken13559 said:
Ralph, indeed that's my thought as well.

The most two 105Ah wet cells are gong to accept is about 52A of charge current in bulk. It sounds like you have a voltage drop issue. If you can't keep the voltage up you'll lose the ability for the batteries to take the optimum current. It also sounds as if your Link monitor may not be working correctly.. The factory reg should be set to about 14.3V +/-..

We ideally need more info to accurately help with your situation.

1- What is the alternator you have now model/brand?
2- How many amps?
3-How does the alternator circuit get back to the batteries?
3A- Do you have an "ammeter" in your engine panel?
4- What gauge wire is used between alternator B+ and battery bank?
5- With the batteries full what it the battery terminal voltage when charging?
6- With the batteries full what is the voltage at the ALT B+ stud?
7- With the battery bank at about 80-85% state of charge what is the B+ voltage?
8- With the battery bank at about 80-85% state of charge what is the batt terminal voltage?
9- With batteries in BULK what is the B+ voltage
10- With batteries in BULK what is the battery terminal voltage?
11- How old are the batteries?
12- Have they ever been equalized?
13- Has the specific gravity been checked?
14- Has every terminal, including alternator case grounding, been cleaned and checked?

I see owners spend gobs of money on alternators and quite often not improve the situation much. Your internal regulator will do BULK and ABSORPTION but will not FLOAT. However, it's a sailboat and FLOAT should not even be a deciding factor as you should rarely be running the engine long enough to hit FLOAT. With two 105 Ah wet cells the most they are going to accept, when dead or in BULK, is about 50-52A of charge current but this will drop. (25% of 210 = 52.5A). If above 80% SOC the accepted current declines fairly rapidly and it can take 10+ hours or more to get back to 100% state of charge, provided you're not experiencing bad voltage drop....

Alan Johnson · Jan 23, 2012

Alternator modification.

On the Catalina 36 site I remember seeing an article by Fred Jackson that gave step by step instructions with pictures on converting a Hitachi alt. to an external requlator. I cannot get into that site now, I think you have to be a member, but I did print out a copy that is on my boat. PM me and give me a fax line if you would like a copy or join the 36 association.

Fitting an external regulator to alternator

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