Specifications

MARATHONNORCO AEROSPACE, INC.
NICKEL-CADMIUM AIRCRAFT BATTERIES
24-34-00
INTRO-2
APR 15/06
DEFINITIONS OF COMMONLY USED BATTERY TERMS
Ampere Hours
A unit of electrical measurement used to describe
the capacity of a cell or battery. The product of
discharge current (in amperes) X the time of
discharge (in hours). It is also used to describe the
amount of electrical energy put back into a battery
during the charging process. Abbreviated as Ah or
Amp. hrs.
Capacity
A measure of the stored electrical energy that is
available from a charged battery. Generally
expressed in Ampere Hours, or as a % of the
nominal (nameplate) capacity
Constant Current Charging
A method used to charge a battery in which a
predetermined, fixed current is passed through it.
Constant Potential Charging (Constant Voltage)
This refers to a method in which a fixed voltage
source is applied across the battery terminals. The
charge current is variable and depends primarily
upon the difference in voltage between the voltage
source and that of the battery. The initial charge
current is high and decreases as the battery accepts
the charge and its voltage increases.
Trickle Charge
A continuous constant current, low-rate charge
(slightly more than the self-discharge rate) suitable
to maintain a battery in a fully charged condition.
Rated or Nominal Capacity
The nominal nameplate capacity rating of a nickel-
cadmium battery generally refers to the number of
Ampere-hours that the battery can deliver when
discharged at the 1-hour rate to 1.0 volt per cell.
"C" Rate
That discharge rate, in nominal or nameplate
amperes, at which a battery or cell will yield its
capacity to a 1.0 volt per cell endpoint in one hour.
Fractions or multiples of the C rate are also used.
C/5 refers to the rate at which a battery will
discharge its capacity in 5 hours. 2C is twice the C
rate or that rate at which a battery will discharge its
capacity in about 1/2 hour. Example: a 25 ampere-
hour battery will have a C rate of 25 amperes, a C/5
rate of 5 amperes and a 2C rate of 50 amperes.
This rating system helps to compare the
performance of different sizes of cells and batteries.
State of Charge
The amount of stored energy (capacity) available in
a rechargeable battery. Usually expressed as a
percentage of its full capacity.
Electrolyte
The conductive medium that provides for the
movement of ions (current flow) between the positive
and negative plates of a cell; an alkaline solution of
Potassium Hydroxide in nickel-cadmium aircraft
cells.
End-of-Charge Voltage
The voltage of a battery at the conclusion of a
charge measured while the battery is still on charge.
Fading
The loss of capacity that occurs when a battery is
cycled with minimal overcharge. A correctable
condition through re-conditioning
Separator
A material that is used to prevent the metallic
contact between the positive and negative plates.
Gas Barrier
A membrane in the separator system that prohibits
the recombination of oxygen (produced at the
positive plate) on negative plate.
Nominal Voltage (Name Plate)
The voltage of a fully charged cell or battery while
delivering current. The nominal voltage of a nickel-
cadmium battery cell is 1.2 volts, therefore a 20-cell
battery would have a nominal voltage of 24 volts,
and a 19 cell is 22.8 volts. (Note: Older batteries
use a different convention for nominal voltage).
Open Circuit Voltage
The voltage of a battery at rest, that is, with no
charge or discharge current flowing