There is a little bump in the bottom of the battery holder (that goes through the hole in the paper). That, and the shape of the battery itself, where the button part sticks out just enough, should keep it from shorting. http://data.energizer.com/pdfs/a76.pdf or the one I usually put in the FM: http://data.energizer.com/pdfs/2l76.pdf The design of the FM is that if the meter works, it is correct. When the battery voltage is too low, it turns off. (With no warning.) The fast drop-off of the 2L76 doesn't help, though.