Battery Car battery charging, how high should voltage go?

Bluecars · Nov 19, 2022

Hi, I bought a car battery charger and plugged it on my car battery to test it (normal battery not AGM). my battery was probably already fully charged because I drove with my car just before using the charger. So this happened: the voltage on the charger started at around 12v? (not sure exactly... maybe a bit lower) and then slowly went up to 15.8v in about 5 minutes then I unplugged it because I wasnt sure if that is normal, I never charged a car battery before. Is it normal that the voltage went that high and how high is it suppoed to go?

OnlQQker · Nov 29, 2022

Alternator will charge a battery when driving, normal sort of reading will be 14.4 when driving or tick over.
A smart alternator will only charge when the battery needs it, but smart alternators only seem to be about in the last 3-4years
A healthy 12v battery will be in the 12.4 - 12.8 range

mainline · Apr 13, 2023

Bluecars said:
Hi, I bought a car battery charger and plugged it on my car battery to test it (normal battery not AGM). my battery was probably already fully charged because I drove with my car just before using the charger. So this happened: the voltage on the charger started at around 12v? (not sure exactly... maybe a bit lower) and then slowly went up to 15.8v in about 5 minutes then I unplugged it because I wasnt sure if that is normal, I never charged a car battery before. Is it normal that the voltage went that high and how high is it suppoed to go?

Was the battery on or off the car ?

Is the volt meter accurate ?

Smart ecu controlled alternators were around in about 2015.