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Old 01-08-2019, 08:44   #1
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External regulators are they interchangeable?

I have a Motorola MA12N600 alternator with an external regulator. I was originally investigating high voltage at the batteries which had a reading of about 15.5V. this was caused by a loose regulator wire which I fixed and that dropped the voltage down to about 13.5 volts at the alternator output terminal and about 13.2 volts at the batteries. I haven't seen this voltage increase even when motoring for multiple hours it just stays at that 13.2 at the batteries. I believe the regulator may be bad and if it is I'm wondering if voltage regulators are interchangeable if I can't find the exact replacement part as I'm cruising currently in Mexico?( Sea of Cortez currently in Santa Rosalia )

The output of the alternator also goes to an ammeter in the cockpit and then to the starter solenoid which I believe is causing some voltage drop.I'm debating on removing the connection to the ammeter in the cockpit and running it directly to the starter with some larger gauge wire as well
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Old 01-08-2019, 08:59   #2
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Re: External regulators are they interchangeable?

After sitting for an hour or more, engine not running, your batteries should be about 12.5 volts. Check that. If that's so, then it is charging at 13.2 when running.
If motoring for several hours, if anything, the regulator should back off asking the alternator to charge.
All that wiring to the ammeter should be small wire. There will be a shunt located somewhere in between so huge cable doesn't have to go to the ammeter.

In theory, the simplest "regulator" is just a wire from battery to the regulator connection on the alternator. This will ask the alternator to put out maximum output until it burns up! A large heavy duty resistor or rheostat in line can adjust that output request.
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Old 01-08-2019, 09:52   #3
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Re: External regulators are they interchangeable?

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Originally Posted by Cheechako View Post
After sitting for an hour or more, engine not running, your batteries should be about 12.5 volts. Check that. If that's so, then it is charging at 13.2 when running.
If motoring for several hours, if anything, the regulator should back off asking the alternator to charge.
All that wiring to the ammeter should be small wire. There will be a shunt located somewhere in between so huge cable doesn't have to go to the ammeter.

In theory, the simplest "regulator" is just a wire from battery to the regulator connection on the alternator. This will ask the alternator to put out maximum output until it burns up! A large heavy duty resistor or rheostat in line can adjust that output request.
The ammeter is an old in line circuit so it has larger cable going to the instrument panel in the cockpit. Which dramatically increases the charging cable length since it then goes to the solenoid. I also believe the wire is undersized for the application (it came from the factory this way).

I check the. Voltage immediately on start up and it is still the lower values of 13.5 at the alternator and 13.2 on the batteries. I would expect the alternator to output a higher voltage intially then ramp down either due to heat or state of charge. Thats why I am thinking maybe it is undercharging due to the low voltage. I have solar panels which end up topping off the batteries so it hasn't been a big deal yet.
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Old 01-08-2019, 10:38   #4
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Re: External regulators are they interchangeable?

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Originally Posted by felizcortez View Post
The ammeter is an old in line circuit so it has larger cable going to the instrument panel in the cockpit. Which dramatically increases the charging cable length since it then goes to the solenoid. I also believe the wire is undersized for the application (it came from the factory this way).

I check the. Voltage immediately on start up and it is still the lower values of 13.5 at the alternator and 13.2 on the batteries. I would expect the alternator to output a higher voltage intially then ramp down either due to heat or state of charge. Thats why I am thinking maybe it is undercharging due to the low voltage. I have solar panels which end up topping off the batteries so it hasn't been a big deal yet.
Are the batteries already full at start up?
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Old 01-08-2019, 10:50   #5
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Re: External regulators are they interchangeable?

Having a cockpit ammeter is 1980 technology. The long wire run, as well as the small wire size, is effectively reducing if not killiing your available charging. In the late 80s (even) Catalina came up with a fix for this: replace the ammeter with a voltmeter in the cockpit, and run the AO to the starter lug, 'cuz there's only one wire from the 1-2-B switch C post. Then, later, the concept of running the AO to the house bank, and using a VSR or even the B position on the switch manually when charging sources were present to charge the start/reserve bank became recommended.


The type of alternator you have is immaterial to your question. What external regulator do you have?
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Old 01-08-2019, 12:20   #6
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Re: External regulators are they interchangeable?

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Are the batteries already full at start up?
No they are not. This would be in the morning after anchoring out and we would have drawn about 60aH from our 470AH bank.
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Old 01-08-2019, 14:20   #7
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Re: External regulators are they interchangeable?

I tried to find a part number on the regulator but it just says Motorola on the outside.

It looks like this one which came up when I searched the alternator.
https://www.motorcityreman.com/moproe8r.html

I pulled apart the connector and the contacts had corrosion on them so I cleaned them off with some sand paper. After the cleaning the output voltage at the alternator was 14.1V and at the batteries was about 13.7V. So I feel better that the regulator is functioning at least closer to how it should. Now I need to bypass the ammeter in the cockpit and go straight to the starter. I will also pick up a spare regulator when I make a trip back to the States

I have a house bank and a starter battery. The starter is charged off an ACR from the house bank.
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Old 02-08-2019, 14:24   #8
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Re: External regulators are they interchangeable?

If you use an external voltage regulator be sure your alternator does not have or use a concurrent internal voltage regulator.

I run a Balmar external regulator that can be used with any alternator not using an internal regulator. The Balmar can be programmed for any battery charging profile to accommodate almost all battery types.
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Old 02-08-2019, 15:05   #9
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Re: External regulators are they interchangeable?

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Originally Posted by felizcortez View Post
I tried to find a part number on the regulator but it just says Motorola on the outside.

It looks like this one which came up when I searched the alternator.
https://www.motorcityreman.com/moproe8r.html
>>>>>>>>>>>>>>>

If it's slapped on the back of your alternator, it is what is called an internal regulator.


Good news on the rest of your post.
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Old 02-08-2019, 16:08   #10
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Re: External regulators are they interchangeable?

A pic would quickly clear up whether its internal or external.
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Old 02-08-2019, 16:40   #11
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Re: External regulators are they interchangeable?

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Originally Posted by belizesailor View Post
A pic would quickly clear up whether its internal or external.

The link he sent has a picture of something he said is similar to what he has.
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Old 02-08-2019, 16:43   #12
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Re: External regulators are they interchangeable?

Quote:
Originally Posted by felizcortez View Post
I tried to find a part number on the regulator but it just says Motorola on the outside.



It looks like this one which came up when I searched the alternator.

https://www.motorcityreman.com/moproe8r.html



I pulled apart the connector and the contacts had corrosion on them so I cleaned them off with some sand paper. After the cleaning the output voltage at the alternator was 14.1V and at the batteries was about 13.7V. So I feel better that the regulator is functioning at least closer to how it should. Now I need to bypass the ammeter in the cockpit and go straight to the starter. I will also pick up a spare regulator when I make a trip back to the States



I have a house bank and a starter battery. The starter is charged off an ACR from the house bank.


So that thing, while external to the alternator, isnít really in the spirit of a good external regulator. Good news though is that you should be able to easily attach a good multistage regulator up using those wire connections.

But it sounds like youíve got some electrical housekeeping to do before considering anything more fancy.
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Old 02-08-2019, 17:09   #13
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Re: External regulators are they interchangeable?

Quote:
Originally Posted by Stu Jackson View Post
The link he sent has a picture of something he said is similar to what he has.
Got it.
Quote:
Originally Posted by Sailmonkey View Post
So that thing, while external to the alternator, isnít really in the spirit of a good external regulator. Good news though is that you should be able to easily attach a good multistage regulator up using those wire connections.

But it sounds like youíve got some electrical housekeeping to do before considering anything more fancy.
Yeah, that appears to be just an automative style regulator (fixed voltage set point) regardless of how its mounted.

OP:

You can replace same with same easily and inexpensively, but a good external regulator will do a better job of charging your batteries. Unfortunaltely, at about 10x the cost.

How do you use your boat? If its just for trips of a few days and then back on shore power for a while then the less sophisticated and less expensive regulator may meet your needs.

Having a spare aboard is a good idea too.
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Old 02-08-2019, 17:16   #14
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Re: External regulators are they interchangeable?

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Originally Posted by belizesailor View Post
Got it.
Yeah, that appears to be just an automative style regulator (fixed voltage set point) regardless of how its mounted.

OP:

You can replace same with same easily and inexpensively, but a good external regulator will do a better job of charging your batteries. Unfortunaltely, at about 10x the cost.

How do you use your boat? If its just for trips of a few days and then back on shore power for a while then the less sophisticated and less expensive regulator may meet your needs.

Having a spare aboard is a good idea too.

Good advice.


Here's more: do not add an external regulator to your Motorola OEM. They are NOT made for the hard running an eternal regulator will demand. Most usually, an external regulator is added once a skipper commits to a larger alternator.


belize is right, if with the cleanup you've done you're getting good charging voltages, stick with it until you upgrade your system.


All the best.
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Old 02-08-2019, 18:35   #15
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Re: External regulators are they interchangeable?

I used one like that once. it will get you by, but use it as an emergency back up regulator, get something better. That thing will burn the alternator.
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