Normal Car Battery Voltage When Off. With the negative terminal disconnected a healthy car battery will only self-discharge at 5 per month. Connect the probes.
Then touch the blacknegative probe to the blacknegative battery terminal. If the voltage is not 125 the battery is dying. A good car battery should read 124-129 volts when the car is off.
If you dont 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.
Causes of Overnight Car Battery Voltage Drop Posted September 12 2019 by Liz filed under Cars. The normal voltage needed to start the car begins from 126 volts. Its power drops from 100 to 25. If the battery isnt fully charged it will diminish to 124V at 75 12V when its only operating at 25 and down to 119V when its completely discharged.
