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  #1   IP: 64.32.196.134
Old 08-03-2008, 11:06 PM
SEMIJim SEMIJim is offline
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Battery Switch: Field Disconnect Protection

After getting under way under sail yesterday, I switched from "BOTH" to "1". The VHF radio beeped and the GPS powered off. So either the switch on our 32-year-old boat is not a make-before-break switch or it's just plain gotten old. Either way: Time for a new switch.

Assuming our A4 has the original Motorola 35A alternator on it: Can I use the field disconnect protection "OFF/1/BOTH/2" switches that are so-equipped offer? I believe the original had an external regulator, and, if I understand correctly, that's what's needed to use this feature.

Secondly: Would a switch rated at 250 amps continuous, 360 amps momentary be sufficient for an A-4?

Heck while I'm at it: Wrenched on engines a lot in the past, but never had cause to do more than occasionally just out and replace alternators whole-sale. So how do I tell the difference between the original 35A Motorola and an upgrade? Between an alternator with an external regulator (as I understand the original would be?) and one with an internal regulator?

Thanks,
Jim
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  #2   IP: 142.68.101.28
Old 08-04-2008, 06:04 AM
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I've been trying to figure this out too. Bought a new switch recently.

1. I understand the A4 has a maximum cranking current less than 200A. Don wrote "we believe that a 200 amp fuse would be a good choice to provide for starter operation" in http://www.moyermarine.com/forums/showthread.php?t=1044 and "The amp draw varies considerably depending on outside air temperature, compression values, etc., but we've never seen over 200 amps." in http://www.moyermarine.com/forums/ar...hp/t-1168.html.

2. Below is a photo of our alternator. I think the external regulator is the silver device attached to the front. I tried to figure out using Google which wire might be the field wire, but gave up -- too many variations between models over the years. It might even be inside the regulator/alternator connection, not outside. My plan is to take it to an alternator shop to check it out anyway, since it is only charging 13.1 volts. I'll ask them then.

Update 10 August 2008: I took the alternator off and found a label on the external regulator. The Internet is a wonderful thing:
http://195.125.241.148/cgi-win/product.exe?M5197A
Transpo M5-197A REG MO 12V
replacing OE MOTOROLA 105-197 5-197 8 RG 2010A
Voltage Set Point: 15.0 V
Regulation: B-Circuit
Adjustable Voltage
Short Key Hole Case Style
Terminal Identification:
PLUG-TYPE: K
WIRING CODE 3
RED...................ISOLATION DIODE(+)
BLACK .............GROUND
GREEN..............FIELD
YELLOW...........IGNITION

There is no green wire visible, so as I suspected it must be inside the casing, so not easy to interrupt it to run to the battery switch field disconnect terminals.
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Last edited by rigspelt; 01-14-2010 at 05:21 AM. Reason: Added photo with regulator removed.
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  #3   IP: 75.199.196.192
Old 08-04-2008, 08:03 AM
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Assuming you're referring to the field exciting lead that connects to the
positive terminal of the coil, that connection is not actually needed to
keep the alternator online, once it activates. In other words, you can
disconnect that lead and the alternator will continue to operate.

Don
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Old 08-04-2008, 08:56 AM
SEMIJim SEMIJim is offline
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Quote:
Originally Posted by Don Moyer View Post
Assuming you're referring to the field exciting lead that connects to the
positive terminal of the coil, ...
I honestly have no idea.


Quote:
Originally Posted by Don Moyer View Post
... that connection is not actually needed to
keep the alternator online, once it activates. In other words, you can
disconnect that lead and the alternator will continue to operate.
That doesn't sound like it, then. I'm not clueful as to how automotive alternators work, but I get the impression that interrupting this circuit shuts-down the alternator, thus protecting the diodes. Perko, Guest and Blue Sea all make switches that have this feature.

This article contains the following information on this circuit:
Quote:
[Guest] Model 2110, 2100, 2300A, 3100 and 3200 switches feature an alternator field disconnect which interrupts the alternator field when the switch is turned to the "off" position, thus preventing electrical surges in the armature circuit which might burn out the alternator diodes or ancillary equipment.
...
Alternators with EXTERNAL REGULATOR:

Remove regulator field wire (regulator "F" terminal) and connect to new wire leading to Guest battery switch field terminal (either terminal).

Add another wire from the other switch field terminal and connect to regulator "F" terminal.

Use #14 AWG wire for new circuit.

OR

If it is easier to reach the alternator, remove alternator field wire (alternator "F" terminal) and connect to new wire leading to Guest battery switch field terminal (either terminal).

Add another wire from other switch terminal and install to alternator "F" terminal.
Use #14 AWG wire for new circuit.

Alternators with INTERNAL REGULATOR:

The field circuit wire on alternators with internal regulators is located within the alternator housing and it is impractical to use the field disconnect feature.
rigspelt,

Thanks for the info: Re: Main battery switch requirement. Sounds like a 250A continuous, 360A intermittent switch should be sufficient.

As far as the alternator field wire: The description above sounds almost vaguely kind of familiar to me--the "F terminal" part, that is. It's been so long since I've wrenched on engines--especially an engine with an alternator with a detached regulator--that I cannot say for sure. I do vaguely recall having to replace a regulator... once. ISTM it was not mounted on the alternator, itself. Then again: I've poked-around in our P30's engine compartment pretty extensively, by now, and I don't recall seeing anything bolted-on anywhere reminiscent of an external regulator, either.

Update:

So I did a bit of quick research, and immediately found Alternator Good ol' Wikipedia . Contained in that article is this:
Quote:
The field windings are initially supplied via the ignition switch and charge warning light, which is why the light glows when the ignition is on but the engine is not running. Once the engine is running and the alternator is generating, a diode feeds the field current from the alternator main output, thus equalizing the voltage across the warning light which goes out. The wire supplying the field current is often referred to as the "exciter" wire. The drawback of this arrangement is that if the warning light fails or the "exciter" wire is disconnected, no priming current reaches the alternator field windings and so the alternator will not generate any power. However, some alternators will self-excite when the engine is revved to a certain speed.
So it sounds like maybe the wire Don describes is the correct wire, but that the 35A Motorola alternator is of the self-exciting type, so the field disconnect feature on some battery switches can't be used to protect the alternator in case of operator error.

And more info:

Atomic Four Specifications (Robert Hess) has this to say:
Quote:
Electrical Charging System: Post 1967 12 volt DC, 35 amp Motorola marine alternator, transistorized alternator-mounted voltage regulator, 12 volt DC solenoid equipped starter (optional 50 amp Motorola marine alternator was available at extra cost)
Don't know what that means with respect to the field (aka: "exciter") wire.

Jim

Last edited by SEMIJim; 08-04-2008 at 10:07 AM. Reason: Additional info
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  #5   IP: 142.68.101.28
Old 08-05-2008, 05:06 AM
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Quote:
Originally Posted by SEMIJim View Post
... sounds like maybe the wire Don describes is the correct wire, but that the 35A Motorola alternator is of the self-exciting type, so the field disconnect feature on some battery switches can't be used to protect the alternator in case of operator error. And more info: (Robert Hess) has this to say: "Post 1967 12 volt DC, 35 amp Motorola marine alternator, transistorized alternator-mounted voltage regulator, 12 volt DC solenoid equipped starter " Atomic Four Specifications . Don't know what that means with respect to the field (aka: "exciter") wire.
Jim
Odd that my 35A Motorola A4 alternator appears to have an external regulator attached, but yours does not. Anyway, we both share the same problem: cannot identify the right wire from which to run a lead to the F connectors on those battery swithches with the Field disconnect feature, to prevent alternator damage if someone accidentally turns off the battery while the engine is running. My conclusion was that maybe the right wire is inside the physical connection between the regulator and the alternator. In the end I decided to get an expert to look at this particular alternator, which I notice is pretty consistent with most of the alternator advice in prior posts here. Seems like there is too much variation in alternator setups for some DIY solutions.

Nigel Calder's Boatowner's Mechanical and Electrical Manual has a good alternator section.
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Old 08-05-2008, 08:30 AM
SEMIJim SEMIJim is offline
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Quote:
Originally Posted by rigspelt View Post
Odd that my 35A Motorola A4 alternator appears to have an external regulator attached, but yours does not.
I don't know that ours does not, I just don't recall seeing anything, off-hand. We may have the same setup you do, and I just never noticed it.

Quote:
Originally Posted by rigspelt View Post
In the end I decided to get an expert to look at this particular alternator, which I notice is pretty consistent with most of the alternator advice in prior posts here. Seems like there is too much variation in alternator setups for some DIY solutions.
It really shouldn't be that difficult. I'll take a look at it next time we're out at the boat, if I think of it.

To be honest: The field disconnect thing isn't awfully high on my priority list. I'd like to have it, as a backup/safety feature, but I don't ever expect we or anybody else to change that switch while we're motoring. ("Expect" is the key word, there, I know .) My immediate concern is stuff powering-down while switching.

So: I may get a switch with the field disconnect or I may not. (Probably will. It doesn't appear to add much cost to the switch.) If I do: I may someday get around to hooking it up--if it's possible, or I may not. It's certainly not important enough to me to pay a marine mechanic to come out and look at it.

Quote:
Originally Posted by rigspelt View Post
Nigel Calder's Boatowner's Mechanical and Electrical Manual has a good alternator section.
I've heard that's a good book. Thing is: I already know electrical systems fairly well, so I don't know as I'd get much out of it. Maybe...

It'll be interesting to see what your mechanic comes up with. Take pictures .

I am kind of surprised the answer isn't here.

Jim
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  #7   IP: 70.108.234.35
Old 08-18-2008, 11:33 PM
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Jim,

I was thinking about adding a capacitor to the alternator to arrest spike voltages encountered when the batteries are not in the circuit. A capacitor would allow the engine and alternator run safely in the OFF position. Old cars used to do this. I haven't had time to spec this out yet, though.

Short of that solution, I am thinking about adding a relay and buzzer to the battery switch field coil connections. The circuit would sound a buzzer when the battery switch is off and the alternator is running.

Steve
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  #8   IP: 206.125.176.3
Old 04-29-2009, 07:46 AM
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sastanley sastanley is offline
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Lightbulb it's been here all along!

Hi all,

Kinda of an old thread, but relevant to my current tasking so no reason to start a new one. My local alternator shop made a comment about voltage adjustable bolt-on regulators for the original 35 amp Motorola when I took one of them in for service.

What I discovered when I bought the boat was the OEM regulator didn't work. The P.O. disconnected the green wire (which I guess is the field wire, and as rigspelt surmised is in between the reg & alt housing, inside the USCG approved ignition protection felty stuff) and ran it to an external regulation source.

Since I am cheap (and own two alternators, one with a new diode plate, and one with no regulator, but otherwise seem to be functioning normally) I was considering sourcing these regulators on the Internet. I have a diode based charge isolator on board, and this takes my original 13.8 volts at the alternator post (still a little low by today's charging standards), and reduces it to about 13.06-13.17v (depending on engine speed) at the battery during charging. Modern charge practices seem to indicate a (wet cell in this case) battery receiving 13.17v will die a slow death due to undercharging, and that number should be more like 14.2v

As usual , rigspelt has already done the research...after I dug thru some non-english websites to find cross reference part numbers for the old regulator, a subsequent Google search with some of those numbers pops up this very thread, because of the information rigspelt posted above with all the cross referencing done.


Now, the question is can anyone find these things on the Internet?? The link above pointing to ASE supply seems to be one of the only places that actually sell them ($23), but I cannot seem to get accurate stock information. The most readily available seems to be the Transpo (M5-197A), or possibly the Amsco (MA-201) regulators.

Thanks!
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"Holiday" - '89 Alura 35 #109
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
http://www.moyermarine.com/forums/signaturepics/sigpic3231_6.gif

Last edited by sastanley; 04-29-2009 at 07:59 AM.
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Old 04-29-2009, 11:26 AM
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Quote:
Originally Posted by SEMIJim View Post
After getting under way under sail yesterday, I switched from "BOTH" to "1". The VHF radio beeped and the GPS powered off. So either the switch on our 32-year-old boat is not a make-before-break switch or it's just plain gotten old. Either way: Time for a new switch.

Assuming our A4 has the original Motorola 35A alternator on it: Can I use the field disconnect protection "OFF/1/BOTH/2" switches that are so-equipped offer? I believe the original had an external regulator, and, if I understand correctly, that's what's needed to use this feature.

Secondly: Would a switch rated at 250 amps continuous, 360 amps momentary be sufficient for an A-4?

Heck while I'm at it: Wrenched on engines a lot in the past, but never had cause to do more than occasionally just out and replace alternators whole-sale. So how do I tell the difference between the original 35A Motorola and an upgrade? Between an alternator with an external regulator (as I understand the original would be?) and one with an internal regulator?

Thanks,
Jim
Sounds like you may have gone through "off" on the way from "both - 1".

"Regardless of setup, an important consideration is that the alternator-to-battery+ connection must never be broken while the alternator is generating current. Otherwise the energy stored in the alternators inductive coils would produce a large voltage spike, possibly destroying both the alternator rectifyer diodes and any connected electronics."
(Boatowners Illustrated Electrical Handbook", Charlie Wing 2006 (P.61).

Wing offers the following solutions to the problem:

1. A voltage snubber from alternator output to ground;

2. a warning sign on the switch;

3. in the case of a four-pole switch, a built-in "field disconnect" (which requires a seperate voltage regulator as opposed to one that is built-in the alternator).

He also suggests a fourth:

4. permantly wiring the alternator output to the "house battery", so there is no danger of damage from interrupting the alternator output. A starting battery can be charged if hooked up with a switch that allows both batteries to be connected in parallel.

and fifth option:

5. both batteries hooked up with a pair of isolation diodes (because the diodes look like closed circuits in the forward direction , they also solve the open-alternator problem). But they also drop charging voltage by .6 - 1.0 volts resulting in chronic undercharging of the batteries!

Guess, you can't get something for nothing!!!

(But if your voltage regulator is adjustable you can compensate by adjusting the output to compensate for the diodes.)
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Old 04-29-2009, 03:32 PM
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Hmmm, #4?

I have problem #5.

I also have a solar trickle charger which I've been testing in the garage over the winter..It seems to bring the battery up just fine after a week or so of strong sunshine, even in winter. Summer should be even better (longer days, more sun.) I put a $25 controller on it (to avoid overcharging), and it seems to pump about 0.7 amps in bright sunshine into the battery. Not a stunning amount, but it is free!

While I contemplate a permanent solution, I am currently considering simply removing the charge isolator from the circuit and keeping the solar charger on the start battery, and the alternator (all whopping 13.8v) connected directly to the house battery. The solar charger should be able to easily bring up the minimal voltage drop from starting the engine if I can't actually start using the house battery, which would be my normal procedure anyway. If necessary I could always move the alternator output back to the isolator if I needed temporary charging of both batteries. All of these items are in close proximity to each other & I have relatively good access on my Catalina 30.
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"Holiday" - '89 Alura 35 #109
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
http://www.moyermarine.com/forums/signaturepics/sigpic3231_6.gif

Last edited by sastanley; 04-29-2009 at 03:41 PM. Reason: rambling on & on & on
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Old 04-29-2009, 10:20 PM
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Quote:
(all whopping 13.8v) connected directly to the house battery.
Hi Shawn,

I am not quite following your explanation. Do you have an external regulator or not? If you have an external regulator it is a simple mod to overcome the diode voltage drops associated with your isolator - with a $2 diode.

Steve
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Old 04-30-2009, 08:39 AM
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sorry, I tend to ramble..i am often not clear :)

Steve,
No I do not have an external regulator. The boat had one at one time (simple one wire automotive type) , but it didn't work either...the charging system on this boat was 'highly modified' by the P.O. What I am attempting to do is at least get it back to original configuration and then move forward from there.

So far, I have sourced another 35amp alternator from a former A-4 owner with the stock regulator, which from what I can tell from my research was designed to put out 13.8v. This has at least gotten me back to a base configuration to work from. Now, I am considering replacing the OEM regulator with a bolt-on replacement regulator that has adjustable voltage. The alternator shop said the alt. itself is pumping out about 15 volts. These aftermarket regulators have a max rating of 15.1v so it sounds like the alt. is OK.

My problem is sourcing this adjustable regulator. In the meantime, I am trying to find a way to get the voltage up in my charging system as far as I can. I already have one dead battery which I assume has been from charging it thru the 'modified' system I inherited along with a diode based isolator. (I did not test the output voltage of the modified system...basically the P.O. built his own regulator with a couple of diodes & a 3-way switch.) The isolator would also be great, if/when I can get 15 volts out of the alternator...I measured each side of the isolator and lose about 0.73 volts or so going thru it.

Again, with the stock 35A Motorola only putting out 13.8v, my goal right now is to eliminate as much wire and junctions as possible, and get as much juice to the battery as possible, while I research alternatives.

So, I am assuming using your suggestion, it tricks the regulator into pumping out more voltage? How does it do that if it is fixed at 13.8v? I thought the job of the regulator was to adjust the amperage put out by the alternator based on its sensing the battery's voltage (state of charge?), I do not understand how you can use a diode to modify the voltage output itself on a fixed unit? - I am a complete amateur at this electrical stuff, so you'll have to bear with me.

In the interest of full disclosure & to try to be less confusing, the boat's previous owner was my father, & he is an electrical engineer and a tinkerer. He has all kinds of weird stuff going on this boat I am trying to figure out. You and him could probably talk shop all day. When I was a kid, he'd draw little diagrams like the one in your post trying to explain what he was doing. I've found a few random hand drawn diagrams in some of the manuals & books I've found in the boat.
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"Holiday" - '89 Alura 35 #109
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD! (no longer a two boat owner!!)
http://www.moyermarine.com/forums/signaturepics/sigpic3231_6.gif

Last edited by sastanley; 04-30-2009 at 08:58 AM. Reason: more rambling ;)
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Old 04-30-2009, 01:55 PM
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Hi Shawn,

Going from the bottom up. . .

Quote:
I am a complete amateur at this electrical stuff, so you'll have to bear with me.
No worries. I am very interested in this topic as my first choice while rewiting my boat was to use isolation diodes, but I bought an ACR instead. I still don't know if that was the best choice, so I an anxious to see your system work properly.

Quote:
I thought the job of the regulator was to adjust the amperage put out by the alternator based on its sensing the battery's voltage (state of charge?)
Yes, the regulator is used to deliver whatever current is necessary to bring the battery voltage up to the charging voltage, 13.8 in your case. Also, the regulator doesn't care about the condition of the battery - or whatever else may be attached - lamps, fans, hair dryer, guitar amp, whatever.

Code:
So, I am assuming using your suggestion, it tricks the regulator into pumping out more voltage?
Yes.

Quote:
How does it do that if it is fixed at 13.8v?
Now the bad news. You have to get in-between the alternator and the regulator. This is probably next to impossible with an integrated regulator, so you will need to not only get an external regulator, but defeat the internal one. And even if you could insert a diode, what would you do when it is time to replace the alternator? Do another mod?

My boat came with the 55 amp unit Don sells and this was the main reason I opted for the ACR. The 55 amp unit has internal regulation. I saw no practical way to use an isolator except with a non-regulating alternator and a separate, external, regulator. Probably not what you wanted to hear. Sorry.

Steve

Last edited by High Hopes; 04-30-2009 at 02:05 PM.
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