Alternator question

[andys2]

Should the alternator be charging the battery all the time? When I test the output from mine, sometimes I get 14.3v and sometimes on 12.2v, is this right or do I have a dodgy alternator? Incidentally, I never get the battery light on, even when it's only showing 12.2v volts and the battery never goes flat.

Andy

[100SRV]

Hi Andy,
typically an alternator does not charge a battery all the time, only when the battery draws current from the alternator (to simplify when the battery voltage is lower than the alternator voltage current flows to the battery until the levels equalize).

Basically a battery serves as a reservoir of power to allow the engine to be started and to provide a reservoir of energy under other conditions.

When the engine is running the alternator supplies all electrical loads until it's maximum output is reached. When this happens the battery "joins in" supplying power - if this situation goes on for too long you end up with a flat battery and will be taking a walk...

Hope this helps
100SRV

[motorwise]

it should show full charge voltage the whole time unless it's an ECU controlled alternator - what car are we talking about?