Maxell 370 SR920W 1.5V Silver Oxide Watch Battery

Overview

The Maxell 370 SR920W is a high‑performance silver oxide coin cell battery designed specifically for wristwatches, small electronic devices, and precision instruments that require a reliable, long‑lasting power source. With a nominal voltage of 1.55 V and an energy capacity of 39 mAh, this compact cell delivers consistent performance over extended periods, making it the preferred choice for timepieces, fitness trackers, and other low‑power applications.

Key Technical Specifications

• Model: SR920W (also marketed as 370)
• Voltage: 1.55 V (nominal)
• Capacity: 39 mAh
• Chemistry: Silver Oxide (Ag₂O/Ag)
• Size: 3.5 mm diameter × 0.9 mm thickness (standard coin cell dimensions)
• Polarity: Positive (+) on the top, negative (–) on the bottom
• Operating Temperature Range: –20 °C to +60 °C (typical for silver oxide cells)
• Shelf Life: Approximately 10 years when stored at room temperature in a dry environment

Silver Oxide Chemistry Explained

The silver oxide battery employs a reversible electrochemical reaction between silver oxide (Ag₂O) and metallic silver. This chemistry offers several advantages:

• Stable Voltage: Silver oxide cells maintain a nearly constant voltage of 1.55 V throughout most of their discharge cycle, ensuring predictable performance for devices that rely on precise power levels.
• Low Self‑Discharge: Compared to alkaline or lithium coin cells, silver oxide batteries exhibit a lower self‑discharge rate (typically around 0.5–1 % per month), which is ideal for watches and other devices left unused for long periods.
• High Energy Density: The 39 mAh capacity in such a small form factor translates to extended operational life, often exceeding two years in typical watch usage.
• Environmental Friendliness: Silver oxide batteries contain no heavy metals or toxic substances, making them more environmentally benign than some alternatives.

Ideal Applications

The Maxell 370 SR920W is engineered for a range of low‑power devices that demand reliable, long‑lasting power. Common uses include:

• Wristwatches – Mechanical and quartz watches, especially those with small button cells.
• Fitness Trackers & Smart Bands – Devices requiring low current draw over months.
• Medical Monitors – Portable pulse oximeters, blood pressure cuffs, and other handheld instruments.
• Remote Controls & Key Fobs – Small electronic accessories that benefit from stable voltage.
• Precision Instruments – Digital calipers, thermometers, and other measurement tools.

Performance Highlights

When compared to competing coin cell technologies, the Maxell 370 SR920W demonstrates:

• Consistent Voltage Output: Maintains 1.55 V until approximately 70–80 % of its capacity is depleted.
• Long Shelf Life: Retains over 90 % of its rated capacity after five years of storage.
• High Current Capability: Capable of delivering up to 5 mA without significant voltage sag, suitable for devices with brief bursts of higher current demand.
• Low Internal Resistance: Typically around 10–15 Ω, which reduces heat generation and improves efficiency.

Installation & Handling Guidelines

Proper installation ensures optimal performance and safety. Follow these steps:

1. Check Polarity: Verify that the positive (+) side of the battery aligns with the device’s positive terminal.
2. Clean Contacts: Use a dry cloth or alcohol wipe to remove any corrosion or debris from the battery contacts.
3. Insert Carefully: Gently slide the cell into place, ensuring it sits flush against the contacts without forcing it.
4. Avoid Short Circuits: Do not touch the battery terminals with metal objects while installing or removing.
5. Store Properly: Keep unused batteries in a cool, dry location. Store them in their original packaging to prevent accidental shorting.

Safety Precautions

• Do not expose the battery to extreme temperatures or direct sunlight for prolonged periods.
• Avoid crushing or puncturing the cell, as this can cause leakage of silver oxide electrolyte.
• If a battery leaks, remove it immediately and dispose of it according to local hazardous waste regulations.
• Never mix new batteries with old or partially discharged ones in the same device.

Environmental Impact & Disposal

The Maxell 370 SR920W is free from heavy metals such as lead, mercury, and cadmium. However, it still contains silver oxide electrolyte that should be handled responsibly:

• Recycle the battery through a certified e‑waste program.
• Avoid incineration or landfill disposal to prevent environmental contamination.

Compatibility Summary

The Maxell 370 SR920W is compatible with any device that accepts a standard 3.5 mm silver oxide coin cell. Common device models include:

• Quartz wristwatches (e.g., Seiko, Citizen, Casio)
• Digital fitness trackers (e.g., Garmin, Fitbit)
• Portable medical devices (e.g., blood pressure monitors)
• Remote controls and key fobs for automotive or home security systems

Why Choose Maxell?

Maxell has a long-standing reputation for producing reliable, high‑quality batteries. The SR920W benefits from:

• Precision Manufacturing: Tight tolerances ensure consistent performance across batches.
Proven Track Record: Widely used in professional and consumer electronics worldwide. Quality Assurance: Each cell undergoes rigorous testing for voltage stability, capacity, and safety.

Conclusion

The Maxell 370 SR920W 1.5 V Silver Oxide Watch Battery delivers dependable power in a compact form factor, making it an excellent choice for any device that requires a long‑lasting, low‑maintenance energy source. Its stable voltage output, low self‑discharge rate, and environmentally friendly composition set it apart as the preferred battery for precision timekeeping and small electronic applications.