User manual

www.enersys.com
Publication No: US-NP-AM-003 • January 2011 15
Glossary of Terms (Continued)
Cutoff Voltage
The final voltage of a cell or battery at the end of charge or discharge
Cycle
A single charge and discharge of a cell or battery.
Discharge Rate
Current taken from a cell or battery and expressed as a fraction
of C (Ampere-hour rating of the cell or battery).
End-of-Charge Voltage
The voltage reached by the cell of battery at the end-of-charge,
while the charger is still attached.
Electrolyte
Conducts ions in the cell. Lead acid batteries use a sulfuric acid
solution.
Energy Density
Ratio of cell or battery energy to unit weight (pound or kilogram)
or unit volume (cubic inch or cubic meter)
Gas Absorption
The ability of the negative plate to absorb oxygen gas generated
within the battery; the greater this ability, the greater the charge
current capability.
High-Rate Discharge
A very rapid discharge of the battery. Normally in multiples of C
(Ampere-hour rating of the cell or battery).
Internal Impedance
The resistive value of the battery to an AC current, expressed in
ohms. Normally measured at 1 khz at full charge.
Low Voltage Cutoff
A sensing device designed to end discharge at a predetermined
voltage level.
Nominal Capacity
The nominal value of rated capacity. In sealed lead acid batteries,
nominal capacity is usually measured at the 20 hour rate.
Nominal Voltage
The nominal value of rated voltage. In lead acid batteries, nominal
voltage is 2 volts per cell.
Open Circuit Voltage The measured voltage of the cell or battery without a load attached.
Overcharge
The continuous charging of a cell after it achieves 100% of
capacity. Battery life is reduced by prolonged over charging.
Parallel Connection
Connection of a group of batteries by inter-connecting all
terminals of the same polarity, thereby increasing the capacity of
the battery group. (Note: Differing brands and/or capacities should
not be connected together).
Primary Cell
A cell which can be discharged only once. Example: Manganese
zinc and alkaline.
Rated Capacity
The capacity of the cell expressed in ampere hours. Commonly, a
constant current for a designated number of hours to a specified
depth of discharge at room temperature.
Resealable Safety Vent
The safety device built into the cell to allow the release of excess
gases and prevent case rupture.
Secondary Battery
A battery which can be charged and discharged repeatedly.
Example: Lead acid and nickel cadmium batteries.
Self Discharge
The loss of capacity of a battery while in stored or unused
condition without external drain.
Separator
The materials which separate the electrodes. In a sealed lead acid
battery, they are usually constructed of micro-porous glass fiber
and additionally serve to retain the electrolyte.
Series Connection
Connection of a group of batteries by interconnecting all terminals
of the opposite polarity, thereby increasing the voltage of the
battery group. (Note: The same rule applies as with parallel
connections).
Service Life
Expected life of a battery expressed in the number of total cycles
or years of standby service to a designated remaining percentage
of original capacity.
Shelf Life
The maximum period of time a battery can be stored under
specific conditions, without supplementary charging.
Standby Service A general term for an application in which the battery is
maintained in a fully charged condition by trickle or float charging
and always ready for use.
Trickle Charge Continuous charging by means of a small current designed to
compensate for self discharge in an unloaded battery
.
Voltage Cutoff A sensing device used to terminate a charge or discharge when
the battery reaches a predetermined voltage level.
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