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  #1  
Old 09-05-2008
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Question Batteries not charging

Ok, here is the problem. When connected to shore power my batteries ( 2 of ) charge up fine. When running the motor the alternator is not charging my batteries. The gage showing the alternator output reads zero. I've removed the alternator and had it tested, it is fine. Has anyone had this problem and what was the solution?
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Old 09-05-2008
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If the alternator is fine, and it uses an internal regulator, but the batteries are not charging?

Either the alternator is not being spun properly (very loose belt or glazed belt so it is slipping badly), OR you have a "one wire" installation which shorts the alternator sense lead back to the output post. In order to get the alternator to kick in, you have to blip the engine, typically to 2-2500rpm to get the initial output from it before it will turn on and regulate itself.
OR you have a wiring problem. Could be your battery terminals or cables or switches, or the harness leads from the alternator, are not making a good contact. Could be there's a blown battery main fuse that's out of sight.
If the belt is nice and clean and tight, and you can't turn the alternator without the belt and flywheel turning, the belt probably is OK.
Check your manual to see if you have a "one wire" setup, or check the wiring to see if the sense wire has been joined back to the output.
Then start checking the rest of the wiring. Note that if the alternator is SPINNING at normal speed, but the sense wire is disconnected, you can blow the alternator out in a minute flat. So check the wiring out before you restart, and then when you restart, use a voltmeter connected directly to the alternator output terminal to see if it really IS putting out.

Odds are something is just not connected.
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Old 09-05-2008
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Check as above. Allow time for the alternator to "ramp up". Measure the voltage at the alternator posts with the engine turning at your cruising speed. If the batteries need charge the voltage should be about 14v. If it isn't and the alternator has been checked out - check the exitation current wiring. If the alternator does not recieve this current through the ignition switch, it will not "ramp up".
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Old 09-05-2008
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Bad wiring?

I just spent a lot of time trying to figure out a similar problem - it looked like a bad voltage regulator... but the manual said that 90% of charging problems are caused by bad wiring. And that turned out to be true.

First I found a pile of bad crimp joints - the previous owner/installer had used automotive connectors and a cheap crimp tool and everywhere I looked I found loose crimps. Got those all fixed... measured voltages and everything was good, until I would try and use it, and then the battery sense voltage dropped from 12.8 to 6.0. Turned out in my case I had a burned wire way back over by 80amp fuse protecting the run from battery to alternator. This was caused by corrosion in non-tinned automotive cable.

Anyway, my advice is to trace out where your wires go and what they do; measure voltages look for loose connections. Its far more likely in a marine environment that a connection has internal resistance from corrosion, bad crimps, loose nuts and so forth than it is that a part goes bad.

The beauty doing this is you will get know your wiring better than you did before, and that will improve the reliability of the combination of your boat and her skipper.


So, on my external voltage regulator, I had a wire from ground, a voltage sense wire connected to the run from the battery, a key switch wire and a field wire running back to the alternator to control it. I had a tachometer wire running from the alternator. There was a ground wire to the alternator and a heavier positive wire from the alternator back to the battery. There may be a separate fuse for that. In my case I had a dual output alternator and some noise suppression transformers (I had to ask someone what the heck they were). Anyway, now I have a spare voltage regulator that I know works (since tried the replacement approach first) and I have a wiring upgrade project on the todo list. But I'm no longer in fear of my charging system.

Good luck.

Last edited by TaylorC; 09-05-2008 at 07:43 PM. Reason: punctuation.
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Old 09-06-2008
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Great forum

I appreciate every ones support so far. This sounds like it is going to be one of those things were you become alot more intimate with your boat. This is good and bad, less time sailing and more time learning the intricacies of Crunch Time. Thank you.
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Old 09-06-2008
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Using non-marine grade wire and cheap crimpers and crimp terminals just isn't worth it on a boat. Get the good ratcheting crimping tool, get decent quality crimp terminals, preferably adhesive-lined heat-shrink tubing ones, and decent marine grade wiring...

That burned wire TaylorC had could have easily been a boat fire that left nothing above the waterline.

Quote:
Originally Posted by TaylorC View Post
I just spent a lot of time trying to figure out a similar problem - it looked like a bad voltage regulator... but the manual said that 90% of charging problems are caused by bad wiring. And that turned out to be true.

First I found a pile of bad crimp joints - the previous owner/installer had used automotive connectors and a cheap crimp tool and everywhere I looked I found loose crimps. Got those all fixed... measured voltages and everything was good, until I would try and use it, and then the battery sense voltage dropped from 12.8 to 6.0. Turned out in my case I had a burned wire way back over by 80amp fuse protecting the run from battery to alternator. This was caused by corrosion in non-tinned automotive cable.

Anyway, my advice is to trace out where your wires go and what they do; measure voltages look for loose connections. Its far more likely in a marine environment that a connection has internal resistance from corrosion, bad crimps, loose nuts and so forth than it is that a part goes bad.

The beauty doing this is you will get know your wiring better than you did before, and that will improve the reliability of the combination of your boat and her skipper.


So, on my external voltage regulator, I had a wire from ground, a voltage sense wire connected to the run from the battery, a key switch wire and a field wire running back to the alternator to control it. I had a tachometer wire running from the alternator. There was a ground wire to the alternator and a heavier positive wire from the alternator back to the battery. There may be a separate fuse for that. In my case I had a dual output alternator and some noise suppression transformers (I had to ask someone what the heck they were). Anyway, now I have a spare voltage regulator that I know works (since tried the replacement approach first) and I have a wiring upgrade project on the todo list. But I'm no longer in fear of my charging system.

Good luck.
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