A normal car battery voltage is between 12.6 and 12.8 volts when the engine is off and the battery is at rest. This indicates a fully charged state. When the engine is running, the charging system takes over, and you should see a voltage reading of 13.5 to 14.7 volts. If your readings fall outside these ranges, it often signals a problem with the battery itself or the vehicle's alternator.
The key to an accurate reading is checking the battery under the right conditions. For a true state-of-charge reading, the car should have been sitting for at least a few hours (this is called the "resting voltage"). Using a simple multimeter is the easiest way to check. A reading below 12.4 volts means the battery is undercharged, and anything at or below 12.0 volts indicates a severely discharged battery that may struggle to start your car.
The following table outlines what different voltage readings typically indicate:
| Condition | Voltage Reading (Engine Off) | What It Means |
|---|
| Fully Charged | 12.6V - 12.8V | The battery is in ideal condition. |
| Charged | 12.4V - 12.5V | Acceptable, but could use a charge soon. |
| Undercharged | 12.0V - 12.3V | The battery is low and may have starting issues. |
| Discharged | 11.9V or lower | The battery is dead or has a faulty cell. |
| Engine Running | 13.5V - 14.7V | The alternator is charging correctly. |
| Engine Running | Above 15.0V | Potential overcharging, which can damage the battery. |
If your battery voltage is consistently low, it's wise to have it tested professionally at an auto parts store. They can perform a load test to see if the battery can hold a charge under the stress of starting the engine, which is the real test of its health.
