How many volts is a dead battery?

A dead battery typically measures around 0 to 12.6 volts. The exact voltage of a dead battery can vary depending on the type of battery and its specific state of charge.

Understanding Battery Voltage

Batteries store electrical energy and provide power to devices by converting that stored energy into electrical current. The voltage of a battery is a measure of the potential difference between the positive and negative terminals, which determines the amount of electrical force available to drive current through a circuit.

A fully charged lead-acid car battery, for example, typically measures around 12.6 to 12.8 volts. As the battery is used and discharged, the voltage will gradually decrease. When the battery is completely drained, the voltage will drop to around 0 to 12.6 volts, indicating that the battery is dead and needs to be recharged or replaced.

Factors Affecting Battery Voltage

The exact voltage of a dead battery can vary based on several factors:

• Battery type: Different battery technologies, such as lead-acid, lithium-ion, or alkaline, have different nominal voltages and discharge characteristics.


• State of charge: The more depleted the battery, the lower the voltage. A completely drained battery will measure close to 0 volts.


• Temperature: Battery voltage can be affected by temperature, with colder temperatures reducing the voltage and warmer temperatures increasing it.


• Load: The voltage of a battery will drop under load, such as when a device is drawing current from the battery.

It's important to note that a voltage reading alone does not always accurately indicate the true state of a battery. Other factors, such as the battery's internal resistance and capacity, should also be considered when evaluating the health of a battery.

Is 12.2 volts a dead battery?

No, 12.2 volts is not necessarily a dead battery, but it is low and indicates the battery is partially charged (around 50–60%) and may struggle to start your car. A fully charged battery should read about 12.6 volts or higher when the engine is off. You should recharge the battery to prevent damage and shorten its lifespan. 
You can watch this video to learn about checking your car battery's voltage: 39sTorqueCarsYouTube · Oct 31, 2023
Understanding your battery's voltage

• Fully charged: A healthy, fully charged battery will show a resting voltage of about 12.6 volts or higher. 
• Partially charged: A reading of 12.2 volts suggests the battery is around 50-60% charged and should be recharged. Running it at this low level for extended periods can reduce its lifespan. 
• Discharged or failing: A reading below 12.0 volts indicates a discharged or failing battery, and a reading of 10.5 volts is considered fully discharged. 

What to do next

• Recharge the battery: Drive your car for about 30 minutes, or use a battery charger, to bring the voltage back up. 
• Monitor the voltage: After charging, test the battery again. If the voltage is still low, or if it fails to hold a charge, the battery may need to be replaced. 

How many volts will a dead battery have?

11.9 volts
A battery is only charged by one quarter at just 12 volts. Once it drops to 11.9 volts, your battery is considered dead. Keep in mind that most modern vehicles demand more power than ever because of all the power needed to operate electronics. To charge your battery using a battery charger, follow the directions below.

Is 12V enough to jump start a car?

If you're wondering what voltage you need in the second battery to start the car, the answer would be approximately 12v. A little under might work. Anything up to 14v will work better. Above 14 you start getting into the territory that the cars electronics will not like it, depending on the vehicle.

Is 12.5 volts a good battery?

A 12.5 volt battery is considered good to excellent, as it indicates the battery is fully or nearly fully charged. While a healthy, fully charged car battery should read between 12.612.612.6 and 12.912.912.9 volts when off, a 12.512.512.5 volt reading suggests the battery is still in good condition, though it may be slightly below its peak charge. To determine if the battery is truly "good" in the long term, it's best to perform a load test. 
This video demonstrates how to test a battery's voltage and what a low voltage might indicate: 52sMobile RV Tech Services (Radar Road Warriors)YouTube · Dec 10, 2023
What the voltage reading means

• 12.612.612.6V to 12.912.912.9V: Excellent, fully charged state. 
• 12.512.512.5V: Good, nearly full charge. 
• 12.412.412.4V: Indicates the battery is about 75% charged, which is still good but not fully charged. 
• Below 12.412.412.4V: The battery is partially discharged. It should be recharged. 
• Below 12.012.012.0V: The battery is significantly discharged and may need to be recharged to avoid long-term damage. 

How to further assess your battery

• Check the voltage when the car is running: A car's alternator should charge the battery, so the voltage should be higher when the engine is running, typically between 13.513.513.5V and 14.214.214.2V. If it doesn't increase, there might be a problem with the alternator. 
• Perform a load test: A load tester simulates the electrical demand of starting the car, which provides a more accurate assessment of the battery's health than a static voltage reading alone. Many auto parts stores will perform this test for free. 
• Clean the terminals: Ensure the battery terminals and cables are clean and free of corrosion, as this can affect the voltage reading and the battery's ability to hold a charge. 

This video explains how to test a 12V battery using a multimeter: 56sVoltloopYouTube · Jul 2, 2023