Working Principle

• Charging: During the charging process, electrical energy is converted into chemical energy. Sulfuric acid reacts with the lead sulfate on the positive and negative electrodes. On the positive electrode, lead sulfate is converted back to lead dioxide, and on the negative electrode, it is converted back to metallic lead.
• Discharging: When discharging, chemical energy is converted into electrical energy. The lead dioxide on the positive electrode and the metallic lead on the negative electrode react with sulfuric acid in the electrolyte to form lead sulfate and water, generating an electric current in the process.

Structure

• Positive Electrode: Usually made of lead dioxide (PbO2​), which has a brown color. It is the electrode where oxidation occurs during discharge.
• Negative Electrode: Composed of metallic lead ($Pb$), which is gray. It is the electrode where reduction occurs during discharge.
• Electrolyte: Consists of a sulfuric acid (H2​SO4​) solution. The concentration of sulfuric acid is an important factor affecting the performance of the battery. During the charging and discharging process, the density of the electrolyte changes as the chemical reactions take place.
• Separator: Placed between the positive and negative electrodes to prevent short - circuits. It allows the passage of ions but blocks the direct contact of the electrodes. Common separator materials include polyethylene, polypropylene, and fiberglass.

Characteristics

• Low Cost: Compared to some other types of rechargeable batteries, lead - acid batteries are relatively inexpensive to produce, which makes them widely used in many applications where cost is a major consideration.
• High Current Output: They are capable of providing high - current discharges, which is suitable for applications that require a large amount of current in a short time, such as starting the engines of vehicles.
• Good Reliability: With a relatively simple structure and mature manufacturing technology, lead - acid batteries have good reliability and stability in normal use.
• Deep Discharge Tolerance: To a certain extent, lead - acid batteries can tolerate deep discharges without significant damage to the battery. However, repeated deep discharges will still affect the battery's life.

Applications

• Automotive Starting: The most common application is in vehicles to provide the initial current for starting the engine. They are also used to power the vehicle's electrical systems when the engine is not running or when the alternator is not generating enough power.
• Uninterruptible Power Supplies (UPS): In the event of a power outage, lead - acid batteries in UPS systems can provide backup power to ensure the continuous operation of critical equipment such as computers, servers, and communication systems.
• Solar and Wind Energy Storage: In off - grid or hybrid renewable energy systems, lead - acid batteries are often used to store the electricity generated by solar panels or wind turbines for use during periods of low generation or at night.