What is in a lead acid battery?

A lead-acid battery is a type of rechargeable battery that uses lead as the primary active material. It consists of several components that work together to store and release electrical energy. Here are the main components of a lead-acid battery:

1. Plates: A lead-acid battery contains a series of lead plates, which are made of a lead alloy. These plates are typically constructed in a positive (cathode) and negative (anode) configuration. The positive plates are coated with lead dioxide (PbO2), while the negative plates are made of pure spongy lead (Pb).

2. Electrolyte: The electrolyte in a lead-acid battery is a solution of sulfuric acid (H2SO4) mixed with distilled water. The concentration of sulfuric acid determines the battery's specific gravity and its overall performance. The electrolyte facilitates the chemical reactions that occur during charging and discharging.

3. Separator: A lead-acid battery has separators placed between the positive and negative plates to prevent them from coming into direct contact and causing a short circuit. The separators are typically made of a porous material that allows the flow of electrolyte while preventing physical contact between the plates.

4. Battery Case: The battery case is usually made of a durable plastic material that holds all the components together and provides insulation. It also serves as a container for the electrolyte.

5. Terminal Posts: Lead-acid batteries have terminal posts that allow for the connection of external circuits and devices. The positive terminal is usually marked with a "+," and the negative terminal is marked with a "-." These terminals enable the flow of electrical current into and out of the battery.

During charging, a chemical reaction occurs that converts lead dioxide on the positive plate to lead sulfate and reduces the pure lead on the negative plate to lead sulfate. This process reverses during discharging, converting the lead sulfate back into lead dioxide and pure lead, respectively, while releasing electrical energy.

Lead-acid batteries have been widely used in applications such as automotive starting batteries, backup power systems, and other industrial applications. They are known for their robustness, affordability, and ability to deliver high current outputs. However, they are relatively heavy and have lower energy density compared to other battery chemistries.