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post #41 of 42 Old 12-10-2011
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Originally Posted by Rockter View Post

Many ships, like mine, need a live ignition to excite the alternator rotor. I have one of those early, and reliable, Ample Power regulators from 1992.

If I turn the ignition off though, I simply do not charge.

I am puzzled as to how any other system would work? How would the alternator be regulated without a power supply? How would it charge?

I don't think it does any harm to my system to turn it off when engine is running, but I simply try never to do it. It has happened every now and again. All that happens is that the alternator amperage just drops to zero.
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Originally Posted by casey1999
The Yanmar manual states (and I think most engine manuals) the alternator can be damaged (rectifier I think gets damaged) if the alternator is disconnected from the battery when the alternator is spinning. Can this happen even if your alternator is self exciting? How is the rectifier actually damaged?

Two possibilities, I think?

1. If the alternator doesn't "see" battery it won't charge, no damage?

2. If it "sees" battery and tries to charge into a "no load" condition the diodes, (rectifier) can be damaged?

By mistake I ran an alternator "open" for a short time and got away with it. from what I have read I was lucky.

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post #42 of 42 Old 12-10-2011
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As an aside to the potential damage to alternator, turning the key off prematurely will turn off oil alarm .So now you pull the stop cord or whatever you have. No way of knowing if engine has actually stopped what with all the partying going on in the cockpit and you release the cord early.Engine gives it's last gasp and bounces on compression sucking salt water into cylinder from manifold, bending one or more con rods I can hear you say "'Only an idiot would do that!" Fortunately the insurgency company paid me for my time and parts and the bruises on my butt are finally fading.
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