Ok, I am guilty of taking all batteries and throwing them.into a drawer. I don't know if they are old, used, full or half full so I hate tossing them in the garbage because they are so expensive. Then I try to find batteties and end up going thru so many just to find some that turn on whatever I'm trying to use. This tester works awesome! I was like a kid with a new toy.. Grabbing all the batteries and testing them. I fully believe its accuracy because i took new batteries and they tested full and pulled the ones out of a dead remote and they came up bad. Another set came up with one still half full. So it will save you money! And better than that it saves you aggravation! Must have for everyone!!