Maxell SR621SW (364) Silver-Oxide Button Cell

A compact 1.55V silver-oxide battery engineered for low-drain devices such as analog quartz watches, calculators, micrometers, and small medical instruments. It delivers stable voltage, excellent leakage resistance, and long service life in suitable applications.

Quick Specs

• Model: Maxell SR621SW (IEC/ANSI: 364)
• Chemistry: Silver oxide (Zn/Ag2O)
• Nominal Voltage: 1.55 V
• Capacity: ~16 mAh (typical; varies by brand and load)
• Dimensions: 6.8 mm diameter × 2.1 mm height
• Weight: ~0.36 g
• Operating Temperature: -10°C to +60°C (14°F to 140°F)
• Shelf Life: Up to 4–5 years at 20–25°C (68–77°F), unopened

When to Choose SR621SW

• Use for low, steady current draw: analog watches without alarms/LEDs, simple calculators, precision measuring tools, and thermometers without power-hungry features.
• Avoid for high-drain bursts: devices with alarms, backlights, or frequent chimes may require the high-drain variant SR621W (363). Match the device’s original code.
• Do not substitute with SR626SW (377): same diameter but taller (2.6 mm). Forcing it can damage contacts or casebacks.

Expected Runtime

Actual life depends on device current, temperature, and age of the cell. Typical estimates:

• Analog quartz watch (no alarm/light): about 2–3+ years
• Calculator or small measuring tool: 1–2 years
• Digital thermometer: months to years depending on usage frequency

Silver-oxide chemistry holds a flat discharge curve, keeping timekeeping accuracy more consistent than alkaline alternatives.

Compatibility and Cross-Reference

Common equivalent codes you may see on devices or packaging:

• 364, SR621SW, SR621
• Brand-specific: Duracell D364, Varta V364, Renata 364, Energizer 364/363

Alkaline lookalikes (e.g., LR621/164) fit but generally provide shorter life and less stable voltage. Use silver-oxide for watches and precision electronics.

Installation and Replacement

1. Open the battery compartment with the correct tool; protect casebacks to avoid scratches.
2. Note polarity before removal. The large flat side is typically the positive (+) terminal.
3. Handle with plastic tweezers or gloves to avoid shorting and skin oils on contacts.
4. Inspect and clean contacts if needed (dry, lint-free swab). Do not bend contact springs.
5. Insert the new cell with the same orientation, secure the compartment, then test.
6. For watches: check the case gasket for wear to maintain water resistance after closing.

Storage and Safety

• Store in original packaging, cool and dry (10–25°C / 50–77°F), away from metal objects.
• Do not mix old and new cells or different chemistries in a device.
• Keep out of reach of children. Button cell ingestion is a medical emergency—seek immediate help.
• Recycle at approved battery collection points. Do not incinerate.

Comparison: SR621SW vs SR621W vs SR626SW

Type	Size (mm)	Drain Type	Approx. Capacity	Typical Use
SR621SW (364)	6.8 × 2.1	Low-drain	~16 mAh	Analog watches, calculators
SR621W (363)	6.8 × 2.1	High-drain	~16 mAh	Watches with alarms/LEDs
SR626SW (377)	6.8 × 2.6	Low-drain	~28 mAh	Watches needing taller cell

FAQ

Can I use SR621W (363) instead of SR621SW?

Both share the same size. Choose SW (low-drain) for simple analog watches and W (high-drain) for watches with power-hungry features. Match the original battery code when possible.

Is SR621SW rechargeable?

No. It is a primary (non-rechargeable) silver-oxide cell. Never attempt to recharge.

Why won’t my watch start after replacement?

Common causes include incorrect polarity, dirty contacts, a pulled crown (stopped position), or a worn movement/gasket. Recheck orientation and cleanliness; if still not working, consult a watch technician.

Can I replace SR621SW with LR621/164?

Physically yes, but not recommended. Alkaline cells have shorter life and a less stable voltage curve, which can affect accuracy.

How should I dispose of used cells?

Recycle through battery collection programs or local hazardous waste facilities. Do not dispose of in household trash.