When you remove your calculators AAA batteries, or if they die, the backup battery powers the calculator so your information is not lost. If you seem to lose programs or variables in your calculator, you may want to replace your backup battery.
Remove the battery cover.
Remove the AAA batteries from the calculator.
Remove the 5mm Philips #00 screw holding backup battery cover.
Remove the backup battery cover.
Use plastic opening tool to remove the backup battery. Place the tool in the small cut-out next to the battery and pry the battery out.