IEEE Std 485-2020 pdf free download – IEEE Recommended Practice for Sizing Lead-Acid Batteries for Stationary Applications.
4. Defning loads
4.1 General considerations
The duty cycle imposed on the battery by any of the conditions described herein depends on the dc system design and the requirements of the installation. The battery supplies the dc power requirements when one or more of the following conditions occur:
a) Load on the dc system exceeds the maximum output of the battery charger
b) Output of the battery charger is interrupted
c) AC power to the battery charger is lost [may result in a greater dc power demand than item b)]
The most severe of these conditions, in terms of battery load and duration, should be used to determine the battery size for the installation.
4.2 Load classifcation
The individual dc loads supplied by the battery during the duty cycle are classified as continuous or
noncontinuous. Noncontinuous loads lasting 1 min or less are designated “momentary loads” and should be
given special consideration (see 4.2.3).
4.2.1 Continuous loads
Continuous loads are energized throughout the duty cycle. These loads are those normally carried by the battery charger and those initiated at the inception of the duty cycle. Typical continuous loads are as follows:
a) Lighting
b) Continuously operating motors
c) Converters (e.g., inverters)
d) Indicating lights
e) Continuously energized coils
f) Annunciator loads
g) Communication systems
h) Power Supplies (e.g., Relay protection, security systems, battery monitors)
4.2.2 Noncontinuous loads
Noncontinuous loads are energized only during a portion of the duty cycle. These loads come on at any time within the duty cycle and remain on for a set length of time, or be removed automatically or by operator action,or continue to the end of the duty cycle. Typical noncontinuous loads may include:
a) Emergency pump motors
b) Critical ventilation system motors
c) Fire protection systems actuations
d) Motor-driven valve operations (stroke time > 1 min)
e) Other ac loads on the output of inverters
4.2.3 Momentary loads Momentary loads can occur one or more times during the duty cycle but are of short duration, not exceeding 1 min at any occurrence. Although momentary loads may exist for only a fraction of a second, it is common practice to treat each load as if it lasts for a full minute because the battery voltage drop after several seconds often determines the battery’s 1-min rating. When several momentary loads occur within the same 1-min period and a discrete sequence cannot be established, the load for the 1-min period should be assumed to be the sum of all momentary loads occurring within that minute. If a discrete sequence can be established, the load for the period is the maximum load at any instant. Sizing for a load lasting only a fraction of a second, based on the battery’s 1-min performance rating, results in a conservatively sized battery. Consult the battery manufacturer for ratings of discharge durations less than 1 min. Typical momentary loads may include:
a) Switchgear operations
b) Motor-driven valve operations (stroke time < 1 min)
c) Motorized switch operations
d) Field fashing of generators
e) Motor starting currents
f) Inrush currents.IEEE Std 485 pdf download.