Lead–acid starter battery basics How many series-connected cells are used to make a nominal 12 V automobile battery?

Introduction / Context:
Automotive starter batteries are lead–acid types made by connecting multiple electrochemical cells in series to achieve the desired nominal voltage for vehicle electrical systems.

Given Data / Assumptions:

• A single lead–acid cell has an open-circuit voltage of about 2.1 V when fully charged.
• The common vehicle system voltage is called “12 V.”

Concept / Approach:
To reach approximately 12–12.6 V at rest, cells are connected in series so that voltages add. The number of cells n is chosen so that n * 2.1 V ≈ 12.6 V (fully charged).

Step-by-Step Solution:

Verification / Alternative check:
Battery casing often shows six filler caps on older designs, corresponding to six cells; modern MF batteries still contain six internal cells.

Why Other Options Are Wrong:

• 2 or 4 cells: would yield about 4.2–8.4 V, insufficient.
• 8 or 12 cells: would produce about 16.8–25.2 V, not a 12 V system.

Common Pitfalls:
Confusing nominal 12 V with exactly 12.0 V; actual voltages vary with state of charge and temperature.

Final Answer: