PURPOSE: To indicate battery life by utilizing elongation of cathode grid by installing piezoelectric device on the inner side of a battery cover and by pressing the piezoelectric device with projection of compression body which is installed in the upper part of an electrode group to generate signal.
CONSTITUTION: A piezoelectric device 3 is fixed on the inner side of a battery cover 2 of sealed type lead-acid battery by adhesive bonding or screw bonding. A projection 5 is installed in a compression body 4, which curves in a convex shape, located in the upper part of an electrode group. The compression body 4 is lifted by elongation of cathode grid which generates at the end of life, and thereby the piezoelectric device 3 is pressed, and signal generated is indicated on an indicator 7. By showing the end of life by elongation of cathode grid, maintenance becomes easy even in a sealed type lead-acid battery whose electrolyte is actually immobilized.
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