The SR721SW/362 battery is a compact, non-rechargeable button/coin-cell type widely utilized in wristwatches, credit card-sized gadgets, remote controls, calculators, medical tools, and similar devices.
This battery variant operates on silver-oxide chemistry, offering an extended shelf life, excellent tolerance to pulse currents, and a broad operating temperature range. While alkaline batteries of identical dimensions are also available, they typically boast shorter shelf lives, lower capacities, and similar characteristics at a slightly reduced cost.
SR721SW/362 Battery Features and Specifications
The SR721SW/362 battery is a silver-oxide button/coin cell, measuring approximately 7.9 x 2.1 mm (0.3110 x 0.0826 inches). It operates at a nominal voltage of 1.55V, with a cutoff voltage of 1.2V, and offers a nominal capacity ranging from 25 to 30 mAh.
Please note that the nominal capacity of the SR721SW/362 battery varies depending on factors such as drain current, battery age, and temperature.
These batteries typically exhibit a self-discharge rate of 5-10% per year, with variations depending on the specific model and storage temperature.
Most SR721SW/362 batteries are designed to operate within temperatures ranging from 0°C to +60°C, although some models may offer wider temperature tolerance.
Additionally, SR721SW/362 batteries may be labeled under various designations such as SR721, SR721W, SR721PW, SR58, 162, 361, 362, SG11, AG11, D361/D362, and similar.
Please note that labels for SR721 batteries are often used interchangeably, with variations indicating specific features:
- SR721: A general-purpose silver-oxide battery measuring 7.9×2.1 mm.
- SR721S: Features sodium hydroxide electrolyte.
- SR721P: Contains potassium hydroxide electrolyte.
- SR721W: Specifically intended for use in watches.
Therefore, SR721SW would denote a silver-oxide battery of the same dimensions with sodium hydroxide electrolyte, typically intended for watch applications.
Some SR721/SR721SW batteries are engineered as low-discharge types (also labeled as 362 batteries), while others are designed for high-discharge scenarios (labeled as 361 batteries).
Additionally, manufacturers may offer multi-drain SR721/SR721SW batteries, often labeled as 361/362 batteries, among other designations.
Below is a comparison chart highlighting key features and specifications of some of the most popular silver-oxide batteries measuring 7.9×2.1mm:
| Battery Datasheet |
Capacity | Operating Temperature | Annual Self-Discharge Rate | Discharge Current |
| Duracell D361/D362 | 24 mAh, 47 kΩ down to 1.2V @20°C | 0°C to +60°C | <10% @20°C | 44.5 μA, 34k8Ω @20°C (Note: datasheet → 47kΩ?!) |
| muRata SR721 | 29 mAh, 30 kΩ down to 1.2V @23°C | -10°C to +60°C | – | 50 μA, 30 kΩ @23°C |
| Renata 361 | 24 mAh, 34k8Ω down to 1.2V @20°C | -10°C to +60°C | <10% @20°C | 44.5 μA, 34k8Ω @20°C |
| Renata 362 | 23 mAh, 34k8Ω down to 0.9V @20°C | -10°C to +60°C | <5% @20°C | 45 μA, 34k8Ω @20°C |
Note that the Duracell D361/D362 battery datasheet indicates a standard discharge current of 44.5 μA over a 47 kΩ load, which seems unattainable for a 1.55V battery. Through calculations, it’s been determined that the required load for such current is 34k8Ω (34.8 kΩ), matching the load used for Renata 361 and 362 batteries.
Alkaline batteries measuring 7.9×2.1 mm are non-rechargeable cells with a nominal voltage of 1.5V, a cutoff voltage of 0.9V, and a nominal capacity of 15-25 mAh, subject to factors like battery age, temperature, and discharge conditions.
These batteries are commonly labeled as LR721, LR58, or AG11, though other designations may be used by some manufacturers.
Compared to silver-oxide batteries of the same size, alkaline versions are typically more affordable but offer smaller capacities, less stable output voltages, and shorter shelf lives. Despite these differences, high-quality alkaline LR721 batteries find widespread use in micro-LED flashlights, toys, medical instruments, calculators, and similar applications.
SR721SW/362 Battery Safety Issues
Contemporary SR721SW/362 batteries are environmentally friendly as they do not contain heavy elements like lead, mercury, or cadmium. However, proper recycling is essential once they reach the end of their lifespan.
In the event of accidental ingestion by pets or children, it’s crucial to contact the nearest emergency center immediately and follow their instructions.
Although these batteries do not contain toxic metals, swallowing them can lead to electrolysis, resulting in severe internal burns. Hence, it’s imperative to keep SR721SW/362 and similar batteries out of reach of children and pets to prevent any potential hazards.
Summary
For a reliable 7.9×2.1 mm non-rechargeable battery, consider the silver-oxide SR721SW/362 multi-drain batteries. These batteries offer stable output voltage, ample capacity, excellent tolerance to surge discharges, and a low self-discharge rate.
Some popular models available include:
- Energizer 362/361 SR721SW Battery
- Maxell 362 SR721SW Watch Battery
- SKOANBE SR721SW 362/361 Watch Battery
While other brands also provide quality batteries in this size, these are among the most popular options. Remember to recycle old batteries responsibly.