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What is a Lead Acid Battery and how do they work.
The lead–acid battery is a type of rechargeable battery. First invented in 1859 by French physicist Gaston Planté, it was the first type of rechargeable battery ever created. Compared to the more modern rechargeable batteries, lead–acid batteries have relatively low energy density and heavier weight.
🔋 How a Lead‑Acid Battery Works
A lead‑acid battery converts chemical energy into electrical energy using a reversible electrochemical reaction between lead (Pb), lead dioxide (PbO₂), and sulfuric acid (H₂SO₄). It’s one of the oldest and most reliable rechargeable battery chemistries, widely used in automotive, industrial, and backup‑power applications.
🧱 1. What’s Inside the Battery
A typical lead‑acid cell contains:
- Positive plate (cathode): Lead dioxide (PbO₂)
- Negative plate (anode): Sponge lead (Pb)
- Electrolyte: Dilute sulfuric acid (H₂SO₄)
- Separators: Porous insulators preventing plate contact while allowing ion flow
- Container: Acid‑resistant plastic or similar materials
Each cell produces about 2.1 volts, so a 12‑volt battery has six cells in series.
⚡ 2. The Discharge Reaction (Supplying Power)
When the battery powers a load:
- Sulfate ions (SO₄²⁻) from the sulfuric acid react with both plates.
- The positive plate (PbO₂) is reduced to lead sulfate (PbSO₄).
- The negative plate (Pb) is oxidized to lead sulfate (PbSO₄).
- Electrons flow from the negative plate → through the external circuit → to the positive plate, creating usable electrical power.
- The electrolyte becomes more diluted because sulfuric acid is consumed.
This is the core of how chemical energy becomes electrical energy.
🔄 3. The Charging Reaction (Reversing the Process)
When a charger applies voltage:
- The reaction reverses.
- Lead sulfate on the plates converts back into PbO₂ (positive) and Pb (negative).
- Sulfate ions return to the electrolyte, increasing the sulfuric acid concentration.
- The battery regains its ability to deliver current.
This reversibility is what makes lead‑acid batteries rechargeable.