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First of all, you probably (unless it freezing temperatures) should not see 14 volts at the battery terminals with the engine running. Usually, it means that the battery is toast (or heavily drained, and will be toast soon - see below) and the alternator is putting out a sizeable amount of current that the battery cannot absorb.
That aside, you should know these things, assuming a healthy battery and alternator:
1) Before starting the engine, with a cold engine compartment (has been sitting overnight), the voltage at the battery should ideally be about 12.65 v.
At 12.2 v, the battery is already half discharged -- and any lower means that the battery is ruined unless it's a "deep-discharge" or "deep-cycle" type.
2) Upon starting the engine, the battery voltage should rise briefly to about 14 v give or take, but that also depends on temperature (higher voltage in the cold, i.e., winter, and lower voltage when warm, i.e., summer), and the condition of the battery just before engine start (fully charged, lower voltage, depleted charge, higher voltage).
[Your alternator's voltage regulator has a built in temperature compensation for this -- not as good as some yacht's temperature sensors at the battery, but then a yacht's battery bank costs thousands of dollars and deserves better monitoring.]
3) After starting the engine, the voltage (in any case) should quickly drop, and level off gradually to about 13.3 v (again, higher in cold weather and lower in hot weather).
4) Any sustained voltage closer to 14 v than to 13.3 v means that electrolyte is boiling off in the battery and the fluid level is dropping (unless you have a non-conventional wet-cell battery, such as a low-maintenance, or newer types) -- you need to check the fluid level (and add distilled water if necessary).
All of the above voltages assume it was made at the battery terminals, not at some dashboard gauge whose connections might have some voltage drop.
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