Knowledge is power - in this case, battery power. You'll know from the easy-to-read gauge on this black-plastic hand held mini-tester whether a battery is good, low or needs to be replaced. The 4-1/4" x 2-3/8" x 1" tester reads "AAA," "AA," "C," "D," 9 volt, 1.5 volt button, and other sizes.
