Quote:
Originally Posted by James_Hatton
I was reading the voltage directly across the battery terminals, with a digital voltmeter.
12.8v without the engine running.
14.4v immediately after starting the engine.
The voltage then gradually drops over a period of about 5 minutes to 14.1v
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The reason you are getting a voltage variation (14.4v @ startup dropping to 14.1v after 5 minutes) is usually due to the battery's state of charge.
If you started the engine with (say) a half charged battery, the alternator would put out the +14v for longer - until the battery was fully charged. Then the perceived volts would start to drop.
Its a moot point about the correct upper voltage that alternators put out, and that's where the voltage regulator plays its part. Personally I have seen dozens of alternator output voltages over the magic 14v , but batteries (and most pieces of electrical equipment) can tolerate this. But @ 14.4v, it may looks a tad high but try driving a few miles with the voltmeter still connected (temporary long leads thro the door or window) and switch on your headlights / fans etc and see how the voltage fluctuates in the real world of driving with varying electrical loads.