Car voltage question

[lotas 10+ year member]

What would it mean if you were driving (RPMs are over 2000) and your car's voltage was at 12.8.......is this normal? It was/is my understanding that when you are idling your cars voltage is around there, but when the alternator is turning fastly i.e. 2000rpms it is 14.4. I see this on my car every now and then, its semi-rare, usually always 14.4 when I am driving but sometimes I'll flip on the voltmeter and it will say 12.8. Whats the deal?

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[M@nJo 10+ year member]

i have a 03 honda civic with an factory 70amp. when i start the car on a cold morning, it reads approxmiately 14.6 volts. after 2-3min of letting the engine warm up, i drive away and it eventually goes down to 14v on light throttle.

after full warm up and 5min of driving, it would go down to 13.x volts when accelerating below 4000rpm (granny driving). at heavy throttle, i see it going down to 12.8/12.9v in most cases.

and this is voltage off my radar detector (the top model passport...forgot what it was called)

 

[ax600 10+ year member]

I had the same problem when I first installed my new set up.

I had a loose ground at the seccond batt.

 

[andy1234 10+ year member]

hmmmm i have a problem with my battery on hot days its charging at 12 then on cold days its charging from 14-15

 

[candyman206 10+ year member]

I got 95 Honda Civic coupe and at cold idle I read 14.4, whe driving I get 14.4, hot idle I get 14.4, big bass note I get 14.4 I still have a stock 70a alt and a old but recently installed autolite battery. If I where you I would got to an auto parts store to have them test your alt and battery. The only time see 12 or below is wit the engine off. I even still get 11.6 after 30 minutes of straight bumpin in a parking lot.