How does a lead-acid battery work ?

Lead-acid batteries work on the principle of converting chemical energy into electrical energy and vice versa. They consist of an electrolyte, plates, and separators. During charging, an external power source applies a voltage higher than the open-circuit voltage of the battery, causing lead sulfate on the positive plate to be converted back into lead dioxide and on the negative plate into metallic lead. During discharging, when a load is connected to the battery, lead dioxide on the positive plate is reduced to lead sulfate, and metallic lead on the negative plate is oxidized to lead sulfate. The electrons flow from the negative terminal of the battery to the load during discharging and from the positive terminal of the external power source to the positive plate of the battery during charging.
How does a lead-acid battery work

How Does a Lead-Acid Battery Work?

Lead-acid batteries are widely used in various applications, from powering vehicles to providing backup energy for homes and businesses. They work on the principle of converting chemical energy into electrical energy and vice versa. Let's delve deeper into the working mechanism of a lead-acid battery:

Components of a Lead-Acid Battery

Electrolyte

The electrolyte is a solution of sulfuric acid (H2SO4) and water. It plays a crucial role in the chemical reactions that occur within the battery.

Plates

There are two types of plates in a lead-acid battery: positive (PbO2) and negative (Pb). These plates are made up of lead alloy grids filled with active materials.

Separators

Separators are porous materials placed between the plates to prevent them from touching each other while allowing the flow of ions through the electrolyte.

Charging Process

When a lead-acid battery is charged, an external power source applies a voltage higher than the open-circuit voltage of the battery. This causes the following reactions:

1. Positive Plate Reaction:

  • PbSO4 + 2H2O → PbO2 + SO4²⁻ + 4H⁺ + 2e⁻
  • The lead sulfate (PbSO4) on the positive plate is converted back into lead dioxide (PbO2).

2. Negative Plate Reaction:

  • PbSO4 + 2e⁻ → Pb + SO4²⁻
  • The lead sulfate (PbSO4) on the negative plate is converted back into metallic lead (Pb).

During charging, electrons flow from the positive terminal of the external power source to the positive plate of the battery, and from the negative plate of the battery to the negative terminal of the external power source.

Discharging Process

When a load is connected to the battery, it starts discharging, and the following reactions occur:

1. Positive Plate Reaction:

  • PbO2 + SO4²⁻ + 4H⁺ + 2e⁻ → PbSO4 + 2H2O
  • The lead dioxide (PbO2) on the positive plate is reduced to lead sulfate (PbSO4).

2. Negative Plate Reaction:

  • Pb + SO4²⁻ → PbSO4 + 2e⁻
  • The metallic lead (Pb) on the negative plate is oxidized to lead sulfate (PbSO4).

During discharging, electrons flow from the negative terminal of the battery to the load, and from the load to the positive terminal of the battery.

Conclusion

In summary, a lead-acid battery works by converting chemical energy into electrical energy during discharging and storing electrical energy as chemical energy during charging. The key components involved in this process are the electrolyte, plates, and separators. By understanding how these components interact and undergo chemical reactions during charging and discharging, we can appreciate the functionality and efficiency of lead-acid batteries in various applications.