LEAD-ACID BATTERY REPLACEMENT TIME RECOGNITION METHOD AND UNITERRUPTIBLE POWER SUPPLY DEVICE USING THE METHOD

PROBLEM TO BE SOLVED: To recognize operation life of a lead battery used for trickle charge in an uninterruptible power supply device with a simple circuit, while a human factor is eliminated and a complex circuit such as a microcomputer is not used. SOLUTION: An electrolytic capacitor 22 which is under identical temperature environment as in a lead battery 21, a ripple-generating circuit 11 which supplies a ripple current to the electrolytic capacitor 22, so as to have the life characteristics of the electrolytic capacitor 22 approximately identical to the life characteristic of the lead battery 21, a comparator 12 which compares a voltage between both the terminals of the electrolytic capacitor 22 with a reference voltage, a transistor 13 which, in accordance with the comparison result to the comparator 12, is turned off, when the voltage between both the terminals of the electrolytic capacitor 22 is lower than the reference voltage and turned on or repeatedly turned on and off, when the voltage between both the terminals of the electrolytic capacitor 22 is higher than the reference voltage and an LED 14 which is extinguished, when the transistor 13 is turned off, lit when the transistor 13 is turned on, and made to flicker when the transistor is repeatedly turned on and off.