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Examoogle • User • info@examoogle.com • EE-2024-8821
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The capacity of a lead-acid cell depends on
rate of discharge
temperature
density of electrolyte
all above
all above
Quick Summary: The capacity of a lead-acid cell, typically measured in Ampere-hours (Ah), is not a fixed constant but is influenced by the operational environment and load conditions. The chemical reaction rate and active material utilization are highly sensitive to external variables, making all listed factors significant.
The capacity of a lead-acid cell, typically measured in Ampere-hours (Ah), is not a fixed constant but is influenced by the operational environment and load conditions. The chemical reaction rate and active material utilization are highly sensitive to external variables, making all listed factors significant.
C=I×t
Cp=Ik×t — Peukert's law where k is the Peukert constant
The capacity depends on the Peukert's law effect where higher discharge rates cause localized depletion of electrolyte and polarization, reducing effective Ah. Temperature impacts the ionic mobility within the electrolyte; lower temperatures increase viscosity, hindering ion diffusion. Electrolyte density determines the concentration of H2SO4, which directly participates in the reversible chemical reaction Pb+PbO2+2H2SO4⇌2PbSO4+2H2O.
Capacity decreases as the discharge rate increases due to Peukert's effect.
Lower temperatures increase electrolyte viscosity, reducing ion migration speed.
Higher electrolyte density indicates a higher concentration of sulfuric acid, which is essential for the reaction.
Lead-acid cells are secondary cells; their chemical active material availability is finite.
High surge current capability
Low self-discharge rate relative to some other chemistries
Low energy-to-weight ratio
Sulfation if left in a discharged state
Automotive starter batteries
Uninterruptible Power Supplies (UPS)
Off-grid renewable energy storage
Standard specific gravity of fully charged lead-acid battery electrolyte is approximately 1.280 at 25°C.
Peukert's law highlights that capacity is variable; discharging faster than the rated (e.g., 20-hour) rate results in a lower available Ah.
D is correct — The capacity is a variable quantity influenced by the discharge current magnitude, ambient temperature, and the chemical density of the sulfuric acid electrolyte.
Always remember that battery capacity is a function of time and rate; it is never a fixed capacity value independent of the load.