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Old 10-19-2019, 01:37 PM   #1
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32v system batteries go dead but alt producing 32v

Hello everyone!!! I own a 1957 71' wooden yacht with three electrical systems on board... a 110v ac, a 12v DC and a 32v dc. My bilge pumps, running lights, some interior lights, and toilets run on the 32v system. I have an awesome charger that does a great job of charging on shore power.

I have a Westerbeke generator that is inop at this time.

Here is my problem... lately when I am running, (two motors, inverter), i notice that the 32v system is rapidly drained. I checked the alternator to see if it was not generating power to charge while that motor (starboard) was running, but it is generating 32v. That is good news in a way... I don't think I have to replace that alternator... but now I have no idea why the batteries would be running down so rapidly. How do I go about searching for the "Vampire" or whatever is sucking these batteries down ahead of the charge coming from the alternator?

I really appreciate the advice. I am keeping the system, so please don't say "Replace the 32v system". Thanks,
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Old 10-19-2019, 03:03 PM   #2
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A nominal 32V system probably needs about 36 volts from the alternator to have enough voltage difference to charge decently. When you measure 32V is it really 32V or is it higher. And if it is near 32V you are probably just reading the battery voltage, not the alternator output voltage. The alternator could be putting out zero, but because it is connected to the battery you are really reading the battery voltage.



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Old 10-19-2019, 03:06 PM   #3
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It takes a voltage differential to pump current into a battery. I'd pull the alternator for a bench test.
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Old 10-19-2019, 03:07 PM   #4
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Thanks, David. I measured with a volt meter exactly 32v from the leads coming off of the alt when the engine was running. Could it be then that the alternator is indeed failing or failed and needs to be replaced? What is the best way to actually test this alternator?
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Old 10-19-2019, 03:09 PM   #5
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Got it. Ok. Good idea and (ugh) I will get right on it.
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Old 10-19-2019, 04:22 PM   #6
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Take the alternator off and take it to an auto electrical shop and have them test it. If it only reads 32V when the alternator is running then it almost certainly is bad.


Another way to check is to measure the current in the output wire with a clamp on DC ammeter. I will bet it is near zero.



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Old 10-19-2019, 07:02 PM   #7
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I had many 32v systems. Charge voltage is around 36v. It could be several items in the alternator. Any larger alternator rebuilder should be able to fix it. It should be rebuilt with new bearings if you don't know the age.

It also could be a corroded connection or ground. Anywhere between the alternator and batteries or within the alternator.
Another option is a 12v to 32v battery to battery charger instead of the 32v alternator and just go to a 12v alt on that engine.





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