Discharge rate directly affects the battery sizing process because it determines the current demands placed on the battery over time. IEEE Std 485-2020 uses discharge characteristic curves to map out the relationship between discharge rates and battery performance, allowing for optimal sizing by ensuring that the total ampere-hours removed does not cause the voltage to fall below the threshold for reliable operation. Adjustments may be necessary based on real-world variations in load and environmental conditions .

IEEE Std 485-2020 provides a method that includes maintaining a cumulative total of ampere-hours removed during the discharge and identifying the discharge current at each point. This information, combined with discharge characteristic curves, allows for determining the cell terminal voltage throughout the duty cycle. For detailed evaluations, the standard outlines step-by-step calculations using 'fan' and 'S' curves, factoring temperature and aging adjustments to ensure accurate voltage predictions .

Sizing lead-acid batteries for stationary applications according to IEEE Std 485-2020 involves defining the dc load and determining the battery's ability to supply this load in float service. Factors such as cell selection, battery duty cycle, and rated capacity are crucial. The document emphasizes keeping the average cell voltage above the specified minimum throughout the duty cycle. Additionally, discharge characteristic curves like 'fan' and 'S' curves are used for calculating cell terminal voltage at various points in the cycle .