PURPOSE: To estimate life by measuring the voltage between a positive electrode terminal and the foot part of a positive plate at the time of sending a current to the positive electrode terminal and a negative electrode terminal, and evaluating the deteriorated state with a value obtained by dividing the measured voltage by the current.
CONSTITUTION: The voltage detecting line and current sending line of a mΩ meter 5 of AC four-terminal method are connected to the positive electrode terminal 7 of a measured battery 6. The current sending line is connected to the negative electrode terminal 8 of the battery, and the voltage detecting line to a voltage detecting terminal 3 connected to the foot part 2 of the positive plate 1 of the battery 6. When the mΩ meter 5 is operated, and alternative current is sent from the terminal 7 to the terminal 8, and a value obtained by dividing the AC voltage component between the terminals 7 and 3 by the sent current is indicated as a resistance value on the mΩ meter 5. This resistance value is increased together with the progress of the life, and about three times the initial value in the life end period. Thus, by measuring the resistance value, the life can be estimated.
YAMAGUCHI KOJI
HIRONAKA KENSUKE
