Casio · Watches
Casio LF-20W-1A battery
1 × 3V lithium coin cell
How to replace it
| Notes | Case-back service typically required; water resistance should be retested after opening. |
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Important
- Module 3551 is outside the OWS 1977–2009 snapshot — battery from Casio product specification (Pattern A), module from Casio US manual search.
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 × CR1616 should restore Casio LF-20W-1A if the battery was the problem. Work through the checks below before replacing the device.
- Check the battery type
This device needs 1 × CR1616 (lithium). Same size does not always mean the same battery.
- Check known model-specific issues
Module 3551 is outside the OWS 1977–2009 snapshot — battery from Casio product specification (Pattern A), module from Casio US manual search.
- 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.
Need to replace the device?
Casio LF-20W-1A is still sold new. Only buy another if a fresh battery and the checks above did not help.