How to Revive a 12 Volt Battery

A 12-volt battery is the most common type of battery in cars. It can lose its charge when you leave an electrical device turned on while the engine is not running. It may be possible to repair a dead battery so that it can hold a charge.

• Socket wrench


• Battery charger


• Voltmeter


• Battery saver device

1. Disconnect the 12-volt wet cell battery with a socket wrench and remove it from the vehicle. Shake it vigorously without spilling the liquid in the cells to dislodge air bubbles between the plates. This technique can add a small amount of charge to the battery.


2. Connect a dead 12-volt battery to an old type of battery charger that produces at least 6 amperes, or amps, of current. New models have circuitry that detects when they are connected to a battery. These types of battery charges may not turn on if you connect them to a battery with a very small charge.


3. Charge the dead 12-volt battery for 10 hours with the battery charger, using the highest level of current the charger can produce. Measure the battery’s voltage with a voltmeter and allow the battery to sit without charging for at least 12 hours.


4. Charge the 12-volt battery for another 10 hours and record the voltage on the battery again. Repeat the charging procedure as long as the battery’s voltage continues to increase. A 12-volt battery can actually produce more than 14 volts when it’s fully charged.


5. Connect a battery saver device to the battery charger if the battery is unable to hold a charge of at least 12 volts. Discharge the battery completely while it is attached to the battery charger to dissolve any sulfate crystals that may be interfering with the battery’s ability to hold a charge. Charge the battery completely and measure the voltage to see if the battery’s maximum charge has increased.