How does a battery work?


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Course Overview

Learning Outcome: After the completion of this section you will be able to explain the basic functions of how a battery works



A battery stores electricity for future use.  It develops voltage from the chemical reaction produced when two unlike materials, such as the positive and negative plates, are immersed and formed in the electrolyte, a solution of Sulphuric acid and water.


In a typical lead acid battery, the voltage of a fully charged battery is approximately 2.1 volts per cell for a total of 12.6 volts.  Electricity flows from the battery as soon as there is a circuit between the positive and the negative terminals.  This will happen when any load that needs electricity is connected to the battery.

What we do not realise is that a lead acid battery operates in a constant process of charge and discharge.  When a battery is connected to a load that needs electricity, current flows from the battery.  The battery then begins to be discharged.

The reverse process is when a battery becomes charged.  This happens when current flows back into it, restoring the chemical difference between the plates.  This takes place when you are driving with or without any accessories and the alternator puts current back into the battery.


As the battery discharges the acid becomes weaker and the voltage drops.  Eventually the battery is so discharged that it can no longer deliver electricity at a useful voltage.

You can recharge a discharged battery by feeding electrical current back into the battery.  A full charge leaves the battery ready to deliver its full power.  This unique process of charge and discharge means that energy can be used and restores over and over again.

For you to understand how a battery works we need to take a look at the construction of a battery.

Course Curriculum

  • Battery Components  0/2

    • Components
    • Battery Components

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