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Athabasca
Athabasca

Posted: Wed Nov 17, 2010 2:43pm

Post Subject: Alternator Voltage too high

I have a question regarding alternator voltage. I have a barrus shires 2000 with twin alternators. One charges three domestic batteries and the other charges the starter battery. There is an Adverc controlling the domestic bank charge voltage. The problem: The adverc is compplaining (flashing green light) and a voltage check with the adverc unplugged shows the domestic battery voltage with the engine running is 15.3 V - enough to fry them! I have had the alternator bench checked by the supplier (it is only 7 months old) and they say that uner controlled test conditions it outputs the standard 14 odd volts (can't remember the exact number. What could be causing the volts to rise when installed (even with the adverc disconnected)? Thanks in anticipation, David Fothergill

Tony-B
Tony-B

Posted: Wed Nov 17, 2010 4:17pm

Post Subject: Alternator Voltage too high

If its a battery sensed alternator rather than a standard machine sensed one then then it could be something causing resistance on the sensing lead but if it is battery sensed I wonder why the Adverc was fitted. A resistive internal connection in the alternator between the main generating part and the voltage regulator could also cause it as could (on some designs) a single blown field diode but that should give a high voltage when on test. I notice you say nothing about any other charging system you may have installed. Some solar regulators and many multi-stage chargers could produce that sort of voltage when they are doing an equalisation charge but not the engine on its own. The typical output voltage AT THE END OF A DAY'S CRUISE with a modern alternator will be between 14.2 and 14.4 volts BUT another major mariniser has been supplying alternators set to 14.8 volts which may well damage traditional battery technology if the batteries are not kept topped up. However again the alternator would do that on the bench as well. All I can suggest is to check to see if the alternator is battery sensing (phone E P Barrus and ask). If not check all charging connections, including those in the multiplug I expect is tucked away somewhere on the wiring loom, and the battery clamps etc. for any signs of anything that may cause resistance. Definitely clean the battery posts and clamps. I would be most interested to find out what is wrong so please come back and tell us when you find out. Tony Brooks

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