Lead–acid battery technology: A “maintenance-free” automotive battery typically uses which plate-grid alloy to minimize water loss and reduce servicing needs?

Introduction / Context:
Maintenance-free automotive batteries aim to minimize electrolyte loss and reduce or eliminate topping-up. The alloying of the lead grids has a major impact on gassing, water loss, and corrosion behaviour.

Given Data / Assumptions:

• Typical 12 V lead–acid automotive battery.
• Closed/sealed with pressure relief, not service-removable caps in most designs.

Concept / Approach:
Lead–antimony grids promote gassing during charge and thus water loss, necessitating periodic topping up. Switching to lead–calcium grids greatly reduces gassing, improving water retention and enabling “maintenance-free” labeling when paired with proper separators and sealing.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer datasheets describe “Ca–Ca” (calcium–calcium) technology for maintenance-free batteries due to lower self-discharge and gassing rates.

Why Other Options Are Wrong:

• Lead–antimony grids: used in serviceable batteries; higher water loss.
• “Does not contain acid” and “does not contain water”: incorrect—these are still lead–acid cells with electrolyte; they are sealed/maintenance-reduced, not empty.

Common Pitfalls:

• Confusing AGM, EFB, and flooded chemistries; all are lead–acid but vary in construction.
• Assuming maintenance-free means no electrolyte present.

Final Answer:
lead-calcium plate grid