[javadog]

A battery will discharge slightly every day when connected to nothing. It can be sitting on a wooden plank, a cloud, or in a Playboy playmate's lap and it will do this.

It will do it faster if the outside of the battery case is dirty.

Your measurements are probably not entirely accurate, especially the first one you took after charging the battery.

If you have a dead cell, your readings would be much lower.

JR