Casio · Calculators
Casio fx-991CW+ UK battery
1 × 1.5V alkaline button cell
Solar-powered in bright light. The replaceable cell below is the backup battery for dim light or storage.
How to replace it
| Notes | Follow Casio user’s guide battery replacement steps for your model. |
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Important
- UK CW+ SKU — same solar+LR44 architecture as fx-991CW
- Casio lists a built-in solar cell. The replaceable cell is the backup/button battery for dim light.
- Do not confuse with fx-570 sibling models that use a single AAA (R03).
Sources
Helpful for this device
Optional tools for opening, testing or charging — separate from the battery answer.
- Fluke 101 Digital Multimeter
Accurate open-circuit voltage and basic electrical checks
- Klein Tools MM400 Multimeter
General DC voltage checks including battery terminals
- Digital multimeter
Measure open-circuit voltage and general electronics checks
New battery but still not working?
A fresh 1 × LR44 should restore Casio fx-991CW+ UK if the battery was the problem. Work through the checks below before replacing the device.
- Check the battery type
This device needs 1 × LR44 (alkaline). Rechargeable cells are not supported for this device. Same size does not always mean the same battery.
- Check known model-specific issues
UK CW+ SKU — same solar+LR44 architecture as fx-991CW Casio lists a built-in solar cell. The replaceable cell is the backup/button battery for dim light. Do not confuse with fx-570 sibling models that use a single AAA (R03).
- Confirm the battery itself
For most coin cells, fitting a known-good fresh cell of the correct code is simpler than capacity testing.
- Still not responding?
If a correct, fresh battery installed properly does not restore the device, the fault may be elsewhere — the device may need service or replacement.