Appendix C Definitions of Terms

DOE-SPEC-3019-96

APPENDIX C

DEFINITIONS OF TERMS

Absorbed Glass Mat

A highly absorbent glass or polymeric fiber mat used to contain

dilute sulfuric-acid electrolyte in absorbed glass-mat type batteries.

These batteries have approximately 70% of the volume of a

comparable flooded-cell battery, so contain a higher concentration

of sulfuric acid (approximate SG = 1.300) to ensure that sufficient

acid is available for reaction. (Otherwise known as a "starved-gel"

cell.)

Aging Factor

A factor used to ensure that a battery will meet its duty cycle

requirement upon initial installation and at its end-of-life. It is

common for batteries to deliver 90 to 95% of rated capacity upon

delivery. Capacity eventually rises to 100%, stabilizes there for a

period of time, then starts to decrease to 80%. Capacity drops

rapidly after reaching 80%, so 80% is assumed to be the point at

which the battery should be replaced. The aging factor used would

then be 1.25 (1/80%).

Battery

Two or more cells electrically connected to form a unit. Under

common usage, the term also applies to a single cell.

Cutoff Voltage

Cell or battery voltage at which the discharge is terminated. The

cutoff voltage is specified by the manufacturer and is a function of

discharge rate and temperature. (Also called end-of-duty cycle

voltage.)

Design Margin Factor

Used to compensate for spare or excess capacity for future loads.

(kd)

The design margin factor can be assumed to be 1.0 for UPS

applications where the battery system is sized for full capacity of the

inverter. For general-purpose applications, the design margin factor

can range from 1.10 to 1.25.

Duty Cycle

The load currents a battery is expected to supply for a specified time

period.

End-of-Duty Cycle

See "Cutoff Voltage."

Equalizing Charge

Charge applied to a battery which is greater than the normal float

charge which is used to completely restore the active materials in

the cell, bringing the cell float voltage and the specific gravity of the

individual cells back to "equal" values.

Float Charge

Method of charging in which a secondary cell is continuously

connected to a constant-voltage supply that maintains the cell in a

fully-charged condition.

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