
d.c. supplies 253
Example 16 What would the efficiency of the battery in Example 15
be if the discharge rate had been 30 A for 5 hours?
30 x 5
Efficiency = = 0.78 or 78%
3
24 x 8
(See program 222, page 252.)
(d) Watt-hour efficiency
Average output power x time
Efficiency =
Average input power x time
For the case of constant current charging
Watt-hours = current in amperes x average voltage x time in
hours
Example 17 A battery is fully charged by a constant current of 15 A
flowing for 8 hours. The average charging voltage is 1.8 V. It is
discharged at a constant current of 10 A flowing for 9 hours. If
the average terminal voltage is 1.3 V, calculat ...