Lead-acid batteries are a type of rechargeable battery commonly used for various applications, such as automotive starting batteries and uninterruptible power supplies (UPS).
- Positive Plate (Cathode): The positive plates are typically made of lead dioxide (PbO2) and are where the oxidation half-reaction occurs during discharge.
- Negative Plate (Anode): The negative plates are made of sponge lead (Pb) and are the site of the reduction half-reaction during discharge.
- Separator: The separator is usually a porous material that physically separates the positive and negative plates while allowing the flow of ions. It prevents short circuits caused by direct contact between the plates.
- Electrolyte: The electrolyte is a solution of sulfuric acid (H2SO4) and water. It facilitates the flow of ions between the positive and negative plates, completing the electrochemical reactions during both charging and discharging.
- Cell Container: The cell container is typically made of polypropylene and serves as the housing for the positive and negative plates, separator, and electrolyte. It also provides electrical insulation and prevents leakage.
- Cell Cover: The cell cover seals the cell container, preventing electrolyte leakage and allowing access for maintenance, including adding water to compensate for water loss due to electrolysis during operation.
- Vent Caps: Vent caps are located on top of the battery and provide a means for releasing gases produced during charging. They also allow for the addition of water to the electrolyte if needed.
- Terminal Posts: The terminal posts are the connection points for external electrical circuits, allowing the battery to deliver electrical power to devices or receive power during charging.
- Internal Connectors: These connect the plates and help in maintaining electrical continuity within the battery.
- Battery Case: The entire battery is enclosed in a case, which may contain multiple cells connected in series or parallel to achieve the desired voltage and capacity.
Lead-acid batteries operate based on the reversible electrochemical reactions of lead and lead dioxide with sulfuric acid. During discharge, lead dioxide is reduced to lead sulfate at the positive plate, while sponge lead at the negative plate is oxidized to lead sulfate. During charging, the reactions are reversed. This cycle allows the battery to store and release electrical energy repeatedly.
