Casio FX-991ES Plus Battery Replacement

Introduction

This guide demonstrates the process of replacing the battery for a Casio FX-991ES Plus calculator. The battery will need to be replaced when a dim or distorted display is noticed, or when the calculator stops working. The calculator is equipped with a solar cell that can provide power to the device, but if the battery becomes old or bloated, it should be replaced in order to prevent leakage that might damage the calculator. Although this calculator uses two-way power, it is inconvenient to depend on having to charge the built-in solar cell when the battery is dead.

What you need

Step 1 Battery

Casio FX-991ES Plus Battery Replacement, Battery: step 1, image 1 of 1

Make sure the calculator is off. If not, turn it off by pressing the [Shift] button then the [AC] [OFF] button.

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Step 2

Flip the calculator upside down and lay it on a flat surface.
Do not press hard on the calculator to avoid turning it on by mistake.

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Step 3

Use a Phillips #0 screwdriver to unscrew the 1.6 mm screw on the battery cover.
Remove the battery cover.
Be gentle while unscrewing the cover, to avoid damaging it.

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Step 4

Casio FX-991ES Plus Battery Replacement: step 4, image 3 of 3

Use a spudger to remove the old battery. Insert it in the empty slot to pry out the battery.
Do not use a sharp item like a knife.
Do not use metal tools, to avoid damaging parts of the battery compartment.