sarah

I recently installed a new Optima Yellow Top Battery D35.
(mostly because I sometimes listen to the stereo while parked,
without the engine on)

Anyway... I've noticed that the battery is only showing a charge of
12.5v or 12.6v, even after nonstop 4-hour driving from NY to PA.
I previously had a 2-year-old Lexus battery which always showed
around 12.8v).

(above voltmeter readings taken after engine has shut off for about
30 minutes or more)

Is this normal? Optima's spec sheet show the D35 should be 13.1v
when fully charged.

dlieu8989

without the engine on, it should be at about 12v and with the engine running, you should see 13.5-14.5

mtparker18

yes, it should be doing this because obviously, when the car is running the alt is charging the battery which will make the volt higher than when not running.