In basic electrical engineering, a lead–acid battery is classified as which type of electrochemical energy storage device?

Introduction / Context:
A lead–acid battery is one of the oldest and most widely used rechargeable energy storage devices. Classifying it correctly helps learners distinguish between single-use cells, rechargeable cells, and devices that directly convert other forms of energy into electricity.

Given Data / Assumptions:

• The device in question is a lead–acid battery used in automobiles, UPS systems, and standby power.
• Electrodes are lead dioxide at the positive plate and spongy lead at the negative plate with sulfuric acid electrolyte.
• Focus is on the category of device rather than detailed construction.

Concept / Approach:
Cell and battery categories include primary (non-rechargeable), secondary (rechargeable), fuel cells (continuous reactant feed), and energy harvesters like solar cells. Lead–acid chemistry is reversible during charge and discharge, which is the defining property of a secondary battery.

Step-by-Step Solution:
Identify charge reversibility: lead–acid cells can be recharged many cycles → secondary category.Contrast to primary: primary cells undergo largely irreversible chemical changes and are discarded when depleted.Contrast to fuel cell: fuel cells convert chemical energy from externally supplied fuels and oxidants without internal recharging.Contrast to solar cell: solar cells convert radiant energy directly to electricity via photovoltaic effect, not via electrolyte reactions.

Verification / Alternative check:
During charging, lead sulfate converts back to lead dioxide and lead, restoring the original active materials. This confirmatory reversibility is characteristic of secondary batteries.

Why Other Options Are Wrong:
Fuel cell: requires continuous fuel and oxidant feed; not a storage battery.Primary battery: not rechargeable by design; lead–acid is rechargeable.Solar cell: uses photovoltaic effect, no electrolyte based redox cycling.

Common Pitfalls:
Assuming all batteries are primary; many common systems are secondary (lead–acid, lithium-ion, nickel–metal hydride).Confusing a fuel cell stack with a rechargeable battery because both involve redox reactions.

Final Answer:
Secondary battery