Things seem to be running a bit slow? Still running slow after you replace the batteries? Why waste time inserting and removing battery after battery when you can just test it.Just get the Gadget Hero's battery tester to help you find useful battery! ˆš Digital Battery Tester Battery Checker for 9V 1.5V and AA AAA Cell ˆš Easy-to-read , digit indicates power level. ˆš Checks power level of 9V and 1.5V batteries ˆš Can quickly test the capacity of your battery. ˆš Test multiple sizes of batteries in one unit ˆš Lightweight and compact, measures 11 X 6 X 2.5 cm ˆš The battery tester tests 9V,1.5V,AA,AAA,C,D and Cell Button Type batteries. Tester does not require any internal batteries to operate. Battery capacity criteria Battery Size 1.5V 9V Good 1.5V~1.28V 9V~7.8V Low power 1.27V~1.15V 7.7V~6V Replace Below 1.15V Below 6V 9V Battery includes 6F22 ,PP3 ,MN1604 The Battery Tester may be used to test the following sizes : 1.5V-----AAA,HP6,MN2400,RO3,AA,HP7,MN1500,UM3 C,HP11,MN1400,UM2,D,HP2,MN1300,UM1 and Cell Button Type batteries. 9V------ PP3,MN1604,6F22,006P NOTE : 1. You can simply test battery voltage to determine whether the capacity of the battery is low or high.It won't directly detect the battery capacity precisely 2.Don't forget : The Battery Tester is activated by the battery being checked .Kepp test times as short as poosible,to avoid unnecessary battery drain. Hold the battery in place with your hand to have a more precise digit. Test multiple sizes of batteries in one unit.(1.5V)AAA,HP16,MN2400,R03,AA,HP7,MN1500,UM3,C,HP11,MN1400,SP11,LR14,UM2,D,HP2,MN1300,SP2,R20,UM1;(9V)PP3,MN1604,6F22,006P.