Diagnosis and Testing

All batteries require routine maintenance to identify and correct problems caused by physical abuse and low electrolyte levels. A visual inspection can identify such physical problems. A state-of-charge test checks the electrolyte strength. And, electrical testing identifies overcharging or undercharging problems. These tests include a capacity, or heavy-load, test.


When testing or servicing a battery, safety should be your first consideration. The electrolyte contains sulfuric acid. It can eat your clothes. It can burn your skin. It can blind you if it gets in your eyes. It can also ruin a car's finish or upholstery. If electrolyte is splashed on your skin or in your eyes, wash it away immediately with large amounts of water. If electrolyte is spilled on the car, wash it away with a solution of baking soda and water.

When a battery is being charged, either by the charging system or by a separate charger, gassing will occur. Hydrogen gas is explosive. Any flame or spark can ignite it. If the flame travels into the cells, the battery may explode.

Safety precautions include:

• Wear gloves and safety glasses.

• Remove rings, watches, other jewelry.

• Never use spark-producing tools near a battery.

• Never lay tools on the battery.

• When removing cables, always remove the ground cable first.

• When connecting cables, always connect the ground cable last.

• Do not use the battery ground terminal when checking for ignition spark.

• Be careful not to get electrolyte in your eyes or on your skin, the car finish, or your clothing.

• If you have to mix battery electrolyte, pour the acid into the water - not the water into the acid.

• Always follow the recommended procedures for battery testing and charging and for jump starting an engine.


Disconnecting the battery will erase the memory on electronic devices. Write down trouble codes and programmed settings before disconnecting the battery.

Also, to prevent damage to electronic components:

• Never disconnect the battery with the ignition ON.

• Never use an electric welder without the battery cables disconnected.

• Never reverse battery polarity.

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