Test micro battery. Check the charge of all 1.2V~4.8V and 9V batteries. Easy to read with digital display. Universal Button Battery Checker Tester AA AAA C D 9V. Place the battery between two points of the battery tester. Easy-to-read display will tell you immediately if there is a fool. Or if you can extend battery life by a few more minutes. The battery tester can be used to test the following.