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Discussion Starter · #1 ·
I have an Ample Power 100 amp small frame and external 3-step regulator. They are working well and have been for decades. The motor is a Volvo MD17C and the main batter bank 275 Ahr gel cell. I have wired the system to allow the disabling of the alternator field wire so that I can swop the battery banks with the motor running.

I have a spare alternator that came off another Volvo engine. It is a Valeo A13N234 alternator (a new one is pictured below). I understand that it is internally regulated and the rectifier diodes are internal also. The one I have appears to have some sort of capacitor hanging from the positive terminal but I don't know where the other end of it goes. Is it some form of snubber?

Is there a visible field wire that I can interrupt prior to switching the battery banks?

I fear if I do not allow the alternator charging to be disabled before I switch the battery banks that I am going to blow the rectifier diodes.

Thanks.

Rockter.
 

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The yellow wire off the back is the voltage sense wire. The black cap is not a capacitor, it is just a spade connector. This wire is connected back to the positive terminal, but it can also be extended directly to your battery bank (recommended).

There is no external field wire because this is an internal regulator. It is easy to modify for an external regulator by connecting a field wire to the appropriate brush and bringing it outside the case. The other brush stays grounded internally. Be aware that this is a N-type alternator, and your regulator might only use P-type. If so, it is easy to convert the regulator by switching the field and ground brushes that the internal regulator currently uses, and remove the internal regulator.

If you just want to switch it off, then that should be able to be accomplished by just turning the ignition key off while you switch batteries, and then back on. The alternator gets its excitation from the key switch. Alternately, connect a switch in line with the D+ terminal to turn it off.

But if you switch batteries a lot, you should get a switch that has a make before break function so that the alternator is never cut off when switching. That way you can just turn the switch and not worry.

BTW, unless you have removed your current rectifier diodes and moved them externally, all alternators have internal diodes.

Mark
 

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Discussion Starter · #3 ·
Col.
Thanks.
My front line alternator and external regulator are working fine.
The alternator in the picture is planned as a reserve.
Am I right in assuming that the D terminal carries the +12V power supply for the alternator to function? I trust that if I connect that to the ignition switch it will serve as a form of charging on/off function and if I temporarily interrupt the 12V supply to the D terminal then that will allow me to switch battery banks without the risk of blown alternator diodes.
?
 

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Col.
Thanks.
My front line alternator and external regulator are working fine.
The alternator in the picture is planned as a reserve.
Am I right in assuming that the D terminal carries the +12V power supply for the alternator to function? I trust that if I connect that to the ignition switch it will serve as a form of charging on/off function and if I temporarily interrupt the 12V supply to the D terminal then that will allow me to switch battery banks without the risk of blown alternator diodes.
?
d+ only gets that alternator energized.Once it is spinning d+ it is not going to shut it off by interrupting d+..
 

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Discussion Starter · #5 ·
I guess this is the problem with internally-regulated alternators. How do you switch battery banks with the engine running? Some seem to use a snubber capacitor across the output terminals? Does that work?
The present set-up with an external regulator allows me to interrupt the field wire.
I guess I could open the internally-regulated alternator and hijack one of the leads to the alternator brushes.
It is rather cramped in there i guess.
 

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If your system uses a 1-2-Both-Off switch, you just go through Both to switch banks. Just don't go through Off. Assumes switch is make before break which most of those switches are.
 

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I guess this is the problem with internally-regulated alternators. How do you switch battery banks with the engine running? Some seem to use a snubber capacitor across the output terminals? Does that work?
The present set-up with an external regulator allows me to interrupt the field wire.
I guess I could open the internally-regulated alternator and hijack one of the leads to the alternator brushes.
It is rather cramped in there i guess.
You just use an ACR...
 

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I have an Ample Power 100 amp small frame and external 3-step regulator.
I am willing to bet that your Ample Power alternator is a General Motors 10DN alternator. They are externally regulated alternators with a one bolt mount. The back side should look like this although the front side might have the enclosed fan rather than the open fan and/or a different v-belt pulley.
If that is right, you can buy one off the internet, or drop by an auto parts store and ask the clerk to go thru their rebuilt 10DN alternators to find one with a 100 amp test report. They are cheap.
 

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Discussion Starter · #10 ·
Guys.
My old 100 amp Ample Power alternator is still going strong with the Ample Power 3 step regulator both from 1992.
When away from the dock it is our only source of battery charging.
I have a spare alternator that I was planning to carry on board but it is internally regulated. It does have a strange capacitor hanging down from one of the terminals that may have been some sort of snubber.
Perhaps I will carry the spare alternator and if I need to use it always start the motor on "all" at the battery master switch and never move the switch when running.
Perhaps I can open the alternator and hijack one of the wires feeding one of the brushes and lead that wire outside to a manual switch?

What is an ACR?

Thanks.
 

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ACR is an automatic charging relay. Connects batteries to charging source when it detects higher voltage from alternator, solar etc.

And as I said in post #6, there is no problem switching between banks as long as you go through Both, not Off. Been doing it for decades and never blown the alternator diodes.
 

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Discussion Starter · #13 ·
Some literature makes great emphasis on the need for the battery master switch to disable the alternator field wire just before the contact is lost when switching. My battery master switch has a separate terminal through which the field wire passes and apparently it must be wired and it is.
Perhaps not all battery master switches are the same?
In the picture I sent can I disable the alternator output by interrupting the yellow wire leading to the positive terminal?
If so I can easily wire in a wee switch to kill the output before switching with motor running.
It is planned as a spare alternator only for emergencies.
 

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In the picture I sent can I disable the alternator output by interrupting the yellow wire leading to the positive terminal?
If so I can easily wire in a wee switch to kill the output before switching with motor running.
It is planned as a spare alternator only for emergencies.
No, that yellow wire is the voltage sense wire for the internal regulator. It has nothing to do with turning the alternator on/off, and interrupting it could cause an over-voltage event as the regulator tries to compensate.

Mark
 
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