Hi, all.
I want to replace my old (probably original) Motorola 55a alternator with a larger amp newer one, and I've been looking over the Technical Articles on the subject. (Thanks for those.) One thing I don't understand yet:
Why would I need an external regulator? Can't I just use the built-in regulator that comes with the alternator?
My engine is the M-25.
—
Ben Ethridge
Miami, FL
1984 MK1 Hull# 263
I did an alternator upgrade a couple of years ago and I used the built-in regulator that was on the alternator. It is working fine. Make sure you review your wiring and have big enough gage wire for the increased current loads from the alt.
Ken Enstrom
2004 C-36 MKII #2199
Tall Rig, Wing Keel, M-35B
S/V Valkyrie - Sail Great Lakes
Interesting question,
My 105 Amp alternator failed this summer. I had gone by Rod Collins article and changed to an external regulator and the system worked well for 10 seasons. In trying to chase down an alternator while cruising this summer I ended up having my son deliver my original alternator to us in Harpswell, ME. Because it had an internal regulator I needed to rethink the way I had wired the external. Well, I completed the changeover and everything functioned absolutely OK. Now I'm thinking this over again and the performance seems to equal the same with the 50Amp and perhaps a bit better....not sure why?
Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine
[quote=benethridge]Hi, all.
I want to replace my old (probably original) Motorola 55a alternator with a larger amp newer one, and I've been looking over the Technical Articles on the subject. (Thanks for those.) One thing I don't understand yet:
Why would I need an external regulator? Can't I just use the built-in regulator that comes with the alternator?
My engine is the M-25.[/quote]
The answer is, like most things, is it depends....
Musings Regarding External Regulation
-Maine Sail
https://www.marinehowto.com/
When to use an internal regulator:
When to consider an external regulator:
External regulators let you more closely taylor your alternator output to your battery capacity, discharge profile, alternator capacity, belt size, and battery chemistry in order to minimize engine run time.
Gary, aside from a faulty 105 amp alternator and external regulator, best guess at why a 50 amp alternator works just as well or even better than your 105 amp alternator is that your batteries during the bulk phase of charging cannot accept more the 50 amps, or at least not for very long. This coupled with the fact that internal regulators tend to have bulk on a timer vs. calculated time (like many external regulators) could account for any slight advantage. Absolutely, if you had batteries that would accept >50 amps for a significant amount of time AND your 105 amp alternator and regulator were working properly, your recharge times with your 105 amp alternator would be less than with a 50 amp alternator. So, best guess is that you have some worn out batteries OR you don't discharge them deep enough for a high capacity alternator to make a difference.
Nick Caballero
Retired C36/375IA Mk II Technical Editor
Nick, you are correct in that I do not believe I let my batteries deplete enough to take full advantage. I also learned about my choices from MaineSails link he attached to his post. Very informative. I have a Balmar BRSll regulator which I chose back when I made the installation and it is preset to 13.6V., but can be changed. I also found info beyond what Balmor supplied at the time. and that I need to digest a bit further. When I have let my batteries deplete significantly the advantage of the 105 Amp alternator is very evident and I do not have to run the engine as long.......more sailing!
Gary Bain
S/V "Gone With The Wind"
Catalina 36', Hull #: 1056, Year: 1990, Engine: M-35
Standard Rig
Moored: Boothbay Harbor, Maine
Home: Auburn, Maine
[quote=GaryB]Nick, you are correct in that I do not believe I let my batteries deplete enough to take full advantage. I also learned about my choices from MaineSails link he attached to his post. Very informative. I have a Balmar BRSll regulator which I chose back when I made the installation and it is preset to 13.6V., but can be changed. I also found info beyond what Balmor supplied at the time. and that I need to digest a bit further. When I have let my batteries deplete significantly the advantage of the 105 Amp alternator is very evident and I do not have to run the engine as long.......more sailing![/quote]
Gary,
13.6V is a battery murdering voltage and charging performance killer..... Flooded batteries need gassing voltages to remain healthy. Bump that voltage to 14.4V - 14.6V for absorption and you will see vast improvements in battery longevity and charging performance. (I am assuming you have flooded batteries) If you never have motor runs longer than 6 hours or so going to 14.7V will be even better.
Also the voltage sensing leads for the regulator should be fed direct to the house bank battery terminals (regulator RED and regulator BLACK wires) if the alternator is also fed to the house bank. Bumping the voltage and providing correct voltage sensing will yield huge improvements in battery life and charging performance. That said it may be too late for your bank if it has been at 13.6V for any length of time....
The BRS regulator is an einexpensive single stage external regulator with minimal benefit. The ARS-5 or MC-614 are a huge leap up in regulator technology...
-Maine Sail
https://www.marinehowto.com/
I'm disappointed to find out that in 2014 solid state internal alternator regulators are not much smarter than the vibrating contact type used in my 1960 Valiant. Doing a bit of research, many internal regulators seem to be based (solely) on the L9407F component. Indeed, the L9407F has thermal compensation which does adjust the field drive, but unfortunatley no real multi-stage attributes. The L9407F is set for a nominal 14.35 volts.
Yes, bump the BRS voltage up if you are going to stick with it. There's an adjustment pot near the spade terminals. Bumping it up to 14.4 volts will at least put it on par with the regulation capabilities of your internal unit. Put a dab of sealant on the pot after adjustment so that vibration does not move it. The BRS being at 13.6 volts certainly can account for part of the difference in performance you have noted.
Nick Caballero
Retired C36/375IA Mk II Technical Editor
[quote=newguy]I'm disappointed to find out that in 2014 a solid state internal alternator regulator is not much smarter than the vibrating contact type used in my 1960 Valiant. Many internal regulators seem to be based soley on the L9407F component. Indeed, the L9407F has thermal compensation which does adjust the field drive, but unfortunatley no real multi-stage attributes.[/quote]
Keep in mind these internal regulatros are simply meant to drive automotive power systems with massive alternators that don't need to work very hard.. My wife's car has a 130A alt and a battery smaller than a G24... All the alt and reg are really doing is powering headlights, stereo, climate control etc. and these alts run at very light duty.. All they do is bulk/CC and absorption voltages/CV and that is all they really need. On newer cars the alt is often controlled by the ECU....
Also not all alternators used on boats use that chip and not all have temp compensation to self protect the alternator. Some do like Hitachi's but the Motorola / Leece-Neville 8MR series marine alts have a 0mV temp gradient. This means no drop in voltage or cut in field voltage as the alt heats up and can mean a cooked alternator when you try and drive a large bank with them.. This is where an external regulator that can current limit or temp compensate can become critical with the Motorola cased alts.
-Maine Sail
https://www.marinehowto.com/
[quote=newguy] This coupled with the fact that internal regulators tend to have bulk on a timer vs. calculated time (like many external regulators) could account for any slight advantage. [/quote]
This is not how internal regulators work. Some internal regs have a temp gradient that reduces the voltage limit of the regulator (mostly Hitachi, Paris Rhone etc.) but all the rest simply work off voltage, as in voltage regulator. Course most factory systems are horribly wired and have massive voltage drop issues so it appears to folks that internal regs work off timers and reduce current early. With proper voltage sensing they would perform identically to an external regulator in bulk, if both absorption voltages were set the same.They do not use timers, this is why they are called voltage regulators...
-Maine Sail
https://www.marinehowto.com/