Casio · Calculators
Casio MS-20YC battery
1 × 1.5V alkaline button cell
Casio MS-20YC uses Two-Way Power: built-in solar plus one LR54 (LR1130) button cell. Slide the bottom battery cover, insert the new cell with (+) facing up, then reseat the cover. Not a solar-only fx-260.
How to replace it
| How to open | On the bottom, press the battery-cover button with a thin tip (not sharp/breakable). While holding the button, slide the cover in the arrow direction, remove the old cell, insert a new LR54/LR1130 with (+) facing up (visible), then reseat the cover. |
|---|---|
| Orientation | (+) side facing up / visible |
| Access | Tool-free |
| Notes | Casio: replace at least every three years even if unused; dim display in low light often means the backup cell is weak. Tax rate / memory can change when battery power is low or during replacement — reset rate if needed. |
Important
- LR54 and LR1130 are the same alkaline size; do not substitute thicker LR44.
- SR1130 is the silver-oxide size twin — only use if the device specifies silver oxide (this Casio guide names LR54/LR1130).
- Sibling SL-310YC shares the same Casio battery guide; confirm the model printed on the calculator.
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 × LR1130 should restore Casio MS-20YC if the battery was the problem. Work through the checks below before replacing the device.
- Check orientation
Confirm the cell is seated correctly: (+) side facing up / visible
- Check the battery type
This device needs 1 × LR1130 (alkaline). Rechargeable cells are not supported for this device. Same size does not always mean the same battery.
- Check known model-specific issues
LR54 and LR1130 are the same alkaline size; do not substitute thicker LR44. SR1130 is the silver-oxide size twin — only use if the device specifies silver oxide (this Casio guide names LR54/LR1130). Sibling SL-310YC shares the same Casio battery guide; confirm the model printed on the calculator.
- 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.
Replacing the device?
Casio MS-20YC is still sold new. Only consider a replacement if the checks above did not help.
Need to replace the device?
Casio MS-20YC is still sold new. Only buy another if a fresh battery and the checks above did not help.