How Many Volts Should A 12 Volt Alternator Put Out. A car alternator needs to be putting out at least 13-14 volts ideally between 138 and 142 volts to effectively charge a 12 volt car battery. If there is a dead or weak cell normal charging voltage cant be achieved on a battery with a bad cell.
The voltage should read a minimum of 13 volts. A good alternator should put out between 135-145 volts. If the alternator is putting out too much voltage 15 volts it is likely your battery acid will boil over out of the battery.
If the battery is low you may want to have it load tested.
How many volts should a marine alternator put out. A car alternator needs to be putting out at least 13-14 volts ideally between 138 and 142 volts to effectively charge a 12 volt car batteryIf the alternator is putting out too much voltage 15 volts it is likely your battery acid will boil over out of the battery. The rule of thumb that states 126 volts equals a fully charged battery and 122 volts means it is 25 percent charged is starting to change with some modern batteries and charging systems. A good alternator should put out between 135-145 volts.
