Car Battery Voltage While Running

When the engine is running this measurement should be 13 7 to 14 7 volts.

Car battery voltage while running. The voltage when the engine is running should be in the range of 13 5 14 7 volts. If this system was in a restored 1966 gt coupe i would probably change the regulator to reduce maximum alternator voltage. Car battery chargers run off ac power and provide 12v dc at relatively low voltages which is the best way to charge a completely dead battery. We only found 10ma draw on the battery when the car was turned off that doesn t seem like enough to drain a battery overnight is something coming on periodically to drain the battery.

When running at a normal slow cruising engine rpm the voltage across the battery terminals should stay over 14 3 volts even with full load like lights heater blower and everything else running. If you don t have a multimeter to tell you the voltage of your battery you can do a test of your electrical system by starting the car and turning on the headlights. If the voltage is lower with engine running than with engine not running something s wrong with your charging system. There is a very big difference when a car battery drops even a small amount of voltage.

When a car drops for instance from 12 6 to 12 0 there will be 75 difference. With the engine running the voltage across the battery posts should read around 16vdc. When your car is running the cars alternator is charging the battery this is why you should see a higher voltage. It can turn out that your battery is just in a state of very long discharge being put away for too long without use.

If you have run across a problem with your car batteries by way of low voltage range or a zero voltage range do not fret. If they are dim that indicates the lights are running off the battery and that little or no charge is. What then should a car battery voltage be while driving. This is the 3rd new battery the alternator tests good 14 3v while running the battery dies overnight but doesn t die if a battery cable is disconnected.

With a reading of a car battery voltage while running over 14 2v and less than 14 8v with the engine running at normal rpm speed and max load you are most likely to have a larger alternator than you need. If you consider buying a new larger alternator when your readings of a car battery while engine running at normal rpm are 14 2 volts also. A fully charged car battery voltage for a vehicle that isn t running should fall between 12 4 volts and 12 6 volts. If your car battery voltage is discharged or has less than 12 4 volts the power decreases dramatically.

Its power drops from 100 to 25. The battery fully charged should read 12 6 vdc with the engine not running. At 12 4 volts a car battery is 75 charged while at 12 2 volts its 50 charged.