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?