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I have a 99 SNOB, 351 carb. My gauge reads 15-16 volts, voltage meter reads 14-15 at the battery and my alternator is putting out 13.5 at idle. How is is possible for voltage to go up at the battery? I can understand a gauge that is off, but my meter should be accurate.
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RE: VOLTAGE QUESTION
That is okay. Batteries always have more than 12V. 13.5 volts (normal) will charge the battery as alternator output is being regulated by the internal regulator due to the battery having a full charge. If the battery were discharged, the alternator would probably show a bit more voltage.
Incidentally, how did you measure this? -
I measured the output at the battery and the alternator with a volt meter. Still showing over 15 on the dash guage.Comment
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To the best of my knowledge:
Fully charged batteries will read about 13.5 volts with no alternator running. Alternators can run between 14 to 14.8 volts, a bit less when at idle. Like DavidF said, the regulator adjusts current and voltage depending on the load so as not to fry the system.
You should see something slightly higher than 13.5 across the battery when in idle or moderate RPM, like 14-14.8 or there abouts.
Check the voltage at the battery with boat off, and boat running, then meter the voltage at the contacts behind the volt gauge. We found that our old boat gauge was off by about 1 volt after a new battery and alternator. This is not uncommon.
My 02 runs at about 14.5 on the gauge when at speed with just the stereo going, this is normal since we have a motor load and the stereo on, this is as it should be, and reads about 13 at idle. Could be a funny gauge.Comment
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