SR920SW Battery: Specs, Equivalents, & Lifespan Guide

Introduction

Known for its stable voltage and long-lasting performance, the SR920SW is a silver oxide button cell battery primarily used in low-drain applications.

Its name reveals important details:

• “SR” stands for silver oxide chemistry
• “920” indicates its dimensions (9.5mm diameter and 2.0mm height)
• “SW” refers to “low drain,” meaning it is engineered for devices that use minimal power over long periods.

This battery runs on a nominal voltage of 1.55V and yields regular power until it runs dry, which qualifies it particularly well as a power source for precision instruments such as analog watches. Ordinarily, it has been used to drive the daily gadgets which include the wrist watches, the calculators and the medical equipment to be able to work most efficiently over a longer duration without frequent replacement. It can be adjusted in narrow areas, and due to the rugged design, it can consistently perform for months or even years.

Its silver oxide chemistry is also one of the best assets of the SR920SW and a reason why this coin cell is favored over the basic alkaline coin cells in most cases. Silver oxide batteries present a consistent voltage value over the lifespan, thus making such devices as watches accurate in time at all times. This chemistry also offers a higher shelf life, usually more than three years, and improved tolerance to temperature alterations, which is relevant in devices that one wears every day, or is exposed to diverse environments. Moreover, silver oxide cells usually possess an increased energy density and leak poorly against respective alkaline cells, a factor that saves delicate electronic components against possible failure.

What is the Equivalent Battery for SR920SW?

The SR920SW battery can be replaced by several equivalent models, as different brands use their naming conventions.  Several model numbers are fully interchangeable with the SR920SW, as long as they share the same physical size (9.5mm diameter × 2.0mm height), silver oxide chemistry, nominal voltage of 1.55V, and low-drain (“SW”) designation. These equivalents include 370. 171. SB-AW, SR69. and D370. all of which will work in devices originally designed for the SR920SW.

• 370 Battery – Perhaps the most well-known equivalent, “370” is widely used by Swiss watchmakers such as Rolex, Omega, and Tissot. Its stable output makes it ideal for analog wristwatches, where precise timekeeping is critical.
• 171 Battery – Often used in calculators, hearing aids, and certain medical devices, the 171 model offers the same long-term reliability and voltage stability as the SR920SW.
• SB-AW Battery – This is Energizer’s designation for the SR920SW, also adopted by several Japanese battery brands. It ensures the same performance standards for both watches and small electronic devices.
• SR69 Battery – Commonly used in Asian markets, especially by Seiko, Citizen, and Casio. It is essentially the same battery, just labeled differently for regional distribution.
• D370 Battery – Duracell’s proprietary code for their version of the SR920SW. This code is typically printed on Duracell packaging and is popular in North America.

While these equivalents perform identically in low-drain devices such as analog watches, small calculators, and measuring instruments, it is essential to confirm the “SW” marking before purchasing.

Is SR920W the Same as SR920SW?

At first glance, the SR920W and SR920SW batteries may appear identical — both are silver oxide button cells measuring 9.5mm in diameter and 2.0mm in height, with a nominal voltage of 1.55V. However, their internal design and discharge characteristics are optimized for very different applications. The main difference lies in their drain type, which determines how they deliver power over time.

The SR920SW is a low-drain battery and as such, was designed to suit devices that draw a relatively small, constant, and prolonged amount of current. This causes it to be used as the choice of analog watches, simple calculators, and precision medical equipment such as glucose meters, where they require a stable voltage to maintain steady performance. To enable battery-powered devices to operate with relative accuracy until the battery is near exhausted, low-drain cells are designed to produce long operational life (life is the time that a battery can operate at a specified capacity) with relatively small voltage drop.

But the SR920W is a high-drain battery (suitable with devices that occasionally require bursts of greater current), as opposed to low-drain (suitable with devices that always require only low current). This form of battery is typical in digital watches with backlights, alarms, stopwatches or multi-function displays where there are sudden power draw surges. These surges are designed to be managed with internal high-drain cells that can survive large feats of voltage sag without failing easily, therefore being more dependable in feature-rich electronics.

Although the two types can be seen as physically interchangeable, inappropriate usage may have an impact on performance and battery life. A high-drain device with an SR920SW will probably discharge drastically quicker and even lead to performance inconsistencies when a lot of power is demanded. On the other hand, although an SR920W can be used in such a low-drain device, it usually has a slightly shorter service life in that device than the SR920SW, due to being designed to be continuously discharged in low current applications instead.

Better to stick to the specification given by the manufacturer of the device to get the best results in the case of choosing between SR920W and SR920SW. The proper match of a drain type not only provides perfect working conditions but also increases the battery life, which decreases the need to replace the battery and prevents erroneous readings of the sensitive equipment.

How Long Does a SR920SW Battery Last?

In typical analog watches—which are considered low-drain applications—the SR920SW can reliably power the movement for 2 to 3 years under normal conditions. This is because analog watches draw a constant but minimal current, allowing the silver oxide chemistry to deliver steady voltage over long periods. In devices with slightly higher current demands, such as small calculators, glucose meters, or other precision medical instruments, the expected life may be closer to 1 to 2 years due to more frequent or variable energy consumption.

One of the big factors of the SR920SW being so successful in increasing operating life is that it has a discharge profile. Silver oxide cells offer a flat voltage curve, whereby the cells tend to hold their nominal voltage of 1.55V until extremely close to the end of capacity. This means that appliances such as clocks and watches can be precise without experiencing slowdowns over time as the battery wears down. Unlike alkaline cells in coin format, where the rate of decline of voltage is more evident, silver oxide cells provide a near-steady performance nearly all the way to a deactivated state.

Unless stored in a cool and dry environment and kept in the original soldered cell packaging (rather than stripped of their packaging individually and stored), the shelf life of SR920SW batteries is 3 to 5 years with negligible capacity loss. Silver oxide is chemically stable; hence, it took a high resistance to self-discharge as compared to other chemistries, although extended usage in excess heat, humidity, or direct sunlight might promote chemical actions within the cell, leading to degradation in its capacity and resulting in a shortened cell life.

To maximize both in-device lifespan and shelf life, it is advisable to:

• Check production or expiration dates to ensure freshness, as even unused batteries slowly self-discharge over time.
• Replace promptly if a device begins losing accuracy or power, as depleted cells can swell or leak, potentially damaging the electronics.

Conclusion

The SR920SW battery, though compact, represents a critical component in the design and operation of precision low-drain electronic devices. Its silver oxide electrochemistry provides flat discharge characteristics resulting in stable 1.55V discharge over a large part of the service life required to achieve accuracy in the analog watch, medical device and measurement instrumentation. Watchmaking professionals, medical instrument professionals and precision electronic professionals find it useful to know of its technical specifications, its suitability for application and the best practices to use and monitor its work and prolonged working lifespan.

Some images are sourced online. Please contact us for removal if any copyright concerns arise.