Citizen · Watches

Citizen EQ0540-57A (Cal. 1002) battery

1 × 1.55V silver oxide button cell

Printed IDs: 1002

Based on: Citizen documentation
Last checked: 8 October 2026
Size: 6.8 × 2.15 mm
Voltage: 1.55 V

How to replace it

Notes	Case-back service typically required; water resistance should be retested after opening. Prefer genuine Citizen cells when available. Do not install a disposable cell in Eco-Drive / rechargeable movements.

Important

Confirm the movement / calibre number stamped on the caseback (left of the case number) — Citizen model families can share names across calibers and Eco-Drive variants.
Eco-Drive and other rechargeable cells (MT*, CTL*, SLB*, …) are excluded from this disposable CR/SR publish set.

Sources

Last checked 8 October 2026

Citizen Watch US Battery Information: Cal. 1002 → SR621SW (non-rechargeable)
Manufacturer support · support.citizenwatch.com
Citizen product EQ0540-57A lists calibre 1002
Manufacturer support · citizenwatch.com

Find more Citizen manuals →How we check sources

Need a SR621SW?

Citizen EQ0540-57A (Cal. 1002) uses 1 × SR621SW.

Buy on Amazon Amazon UK

Buy links go to Amazon (Associates where tagged) or other affiliate programmes when available. They never change the battery answer.

Helpful for this device

Optional tools for opening, testing or charging — separate from the battery answer.

Amazon links may earn us a commission. They do not change the battery answer.

Fluke 101 Digital Multimeter
Accurate open-circuit voltage and basic electrical checks
Docs Buy on Amazon More tools
Klein Tools MM400 Multimeter
General DC voltage checks including battery terminals
Docs Buy on Amazon More tools

Digital multimeter
Measure open-circuit voltage and general electronics checks
Voltage alone does not establish usable capacity, especially for rechargeables.
Tester vs multimeter Buy on Amazon

Buy links are optional and separate from the battery answer.

New battery but still not working?

A fresh 1 × SR621SW should restore Citizen EQ0540-57A (Cal. 1002) if the battery was the problem. Work through the checks below before replacing the device.

Check the battery type
This device needs 1 × SR621SW (silver_oxide). Same size does not always mean the same battery.
Check known model-specific issues
Confirm the movement / calibre number stamped on the caseback (left of the case number) — Citizen model families can share names across calibers and Eco-Drive variants. Eco-Drive and other rechargeable cells (MT*, CTL*, SLB*, …) are excluded from this disposable CR/SR publish set.
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.

These checks follow this device’s orientation, battery type, and important notes from the maker.

Need to replace the device?

Citizen EQ0540-57A (Cal. 1002) is still sold new. Only buy another if a fresh battery and the checks above did not help.