Comment by eezynow

i am an audiologist. this is my go-to method for checking hearing aid batteries on the fly, especially as it lets me work a bit messily.. for better or worse, i now have a habit of ripping fresh batts out out of a packet, without immediately disposing of the old ones i have removed from an aid, while my attention is focused on programming it (older aids often interface using a cable connected to a programming 'pill' which supplies power and data through an empty battery cavity... so i can be putting batteries in and out and programming cables in an out, multiple times in a session with a client... anyhow..) i no longer need to pay attention as to which battery is which, as i just pick up both together and drop them from about a 15cm height.. the old one bounces jauntily away, while the new one stops dead with zero bounce. it is a super accurate trick and the information never fails to astound clients.. it surprised me when i learnt it from an old salt colleague and it surprises me more that it is not common knowledge.. especially amongst my workmates.