Square lithium battery flattened
For AA, AAA, C, and D batteries, slide the flat, negative end of the battery against the spring onto the device. Then, push the raised, positive end into the flat side of the compartment. ... Look at the snaps on top of the 9-Volt battery. A 9V battery is small and square, with two snaps on the top. One is a male connector, and the other is female.