LAMAR BETA D-50 Operating Manual - page 33
APPENDIX A - BATTERY OVERVIEW
Nickel-cadmium batteries are used in auxiliary power units, aircraft engine starting, space
satellite power, missile electrical systems, and electrical propulsion
DEFINITIONS
AMPERE-HOURS.
The term "ampere-hours" is a unit of measure that refers to the
electrical capacity of a battery. It is the product of the current in amperes multiplied by the
period of time in hours during which the current is delivered. For example, a battery that
discharges at 5.0 amperes for 4.0 hours has delivered 5.0 x 4.0 or 20 ampere-hours. To
convert ampere-minutes to ampere-hours, simply divide by 60. E.g. 10 amperes x 40
minutes = 400/60 ampere-hours = 6.6 ampere-hours.
CUTOFF VOLTAGE.
The cutoff voltage is the voltage point on the discharge curve, for a
specified discharge rate, at which the battery or cell is considered to be discharged for all
practical purposes. To discharge beyond this point will yield little useful power due to the
subsequent rapid voltage drop that occurs.
CAPACITY RATE (C
1
-RATE).
The capacity rating of a lead-acid or nickel-cadmium
battery is based on a one hour discharge rate with the battery initially at temperature
77.5°F (25°C) and a cutoff terminal voltage of 18.0 volts for a 24-volt battery or 9.0 volts for
a 12-volt battery. For example, a 24-volt battery rated at 30.0 ampere-hours should deliver
30.0 amperes for a minimum of 1.0 hours before reaching the 18.0 volts cutoff voltage. This
is a one-hour, C
1
-rate discharge.
BETA D-50 TESTER / ANALYZER - OPERATING MANUAL V2.2
Page 31