Lead-Acid Battery

Overview

The lead-acid battery is one of the oldest and most widely adopted rechargeable battery technologies. Despite the rise of lithium-ion batteries in modern EVs, lead-acid units remain relevant due to their low cost, durability, and reliability in providing auxiliary power. In electric vehicles, they are primarily used for 12V systems that power lights, infotainment, and onboard electronics rather than propulsion.

Invented in the 19th century, lead-acid technology has evolved to include sealed, maintenance-free, and deep-cycle variants, making it a staple in both automotive and industrial applications. Its robust design ensures steady performance even under demanding conditions, which is why many EVs continue to rely on it for essential backup and auxiliary functions.

How Does It Work?

A lead-acid battery operates on electrochemical reactions between lead dioxide (PbO₂) at the positive plate, sponge lead (Pb) at the negative plate, and sulfuric acid (H₂SO₄) as the electrolyte.

1. Discharge Phase – During use, lead dioxide and sponge lead react with sulfuric acid to form lead sulfate (PbSO₄), releasing electrical energy.

2. Charge Phase – When recharged, the reaction is reversed, restoring lead dioxide and sponge lead while regenerating the sulfuric acid.

3. Cycle Behavior – Repeated charge-discharge cycles allow continuous use, though efficiency and capacity decline over time.

This straightforward mechanism makes lead-acid batteries robust but less energy-dense compared to lithium-ion alternatives.

Features of Lead-Acid Battery

1. Cost-Effective

   Inexpensive to manufacture and widely available, making it accessible for mass use.

2. Durability

   Resistant to overcharging, electrical surges, and varying temperatures.

3. Low Energy Density

   Provides reliable power but stores less energy per unit weight compared to lithium-ion batteries.

Applications in EV

• Auxiliary Systems: Commonly used in EVs to power 12V electronics, lights, and infotainment displays.

• Backup Power: Serves as a stable energy source for safety-critical systems when the high-voltage battery is off.

• Hybrid Vehicles: In some hybrid EVs, lead-acid batteries manage starter motors or support regenerative braking systems.

• Fleet & Utility EVs: Widely used in electric buses, forklifts, and small utility EVs where cost-effectiveness is critical.

Conclusion

While lead-acid batteries are not the main propulsion source for modern EVs, they remain vital for supporting systems and ensuring safety. Their affordability, dependability, and resilience make them an indispensable part of the EV ecosystem, complementing high-voltage lithium-ion packs and enabling seamless vehicle operation.