Figure 22.

Correction chart.

14. BATTERY RATINGS.

a. The amount of water a can will hold may be measured in pints, quarts, or

gallons. Battery capacity is measured in ampere-hours which are the number of

amperes the battery will deliver multiplied. by the number of hours the battery

will deliver it. For example, suppose a battery will deliver 5 amperes for 20

hours, then 5 amperes multiplied by 20 hours equals 100 ampere-hours. If the

ampere-hour rating is based on nothing more, the rating would change if the rate of

discharge is changed. Suppose that we increase the load on the battery from 5 to

10 amperes. The battery would then produce the 10 amperes for a period less than

10 hours, so its rating would figure to be less than 100 ampere-hours. As you can

see, some form of standard procedures must be used to rate the ampere-hours before

the ratings will mean the same in all tests.

b. The capacity of batteries is rated

by a standard procedure called the

20-hour rating. This rating gives the number

of ampere-hours the battery will

deliver if it is discharged at a uniform rate

for 20 hours, at a temperature of

80, and with a battery voltage of 1.75 volts

per cell at the end of the 20-hour

period.

OS 010, 3-P27