I didn’t have a spudger but a flat 3/32” jeweler’s screwdriver worked just as well. Also, the battery slides out the side, nothing to undo. I slid it out using a jeweler’s screwdriver. (Don’t touch any electrical components or traces with the metal tip.) If you’re not sure the battery is good, turn the unit over and see if there is anything displaying, or run a test operation like 2 x 2 etc. to check before putting the back into place.