AG1/SR621SW Battery Equivalent
SR621SW battery is a non-rechargeable silver-oxide button/coin cell battery, commonly used in watches, toys, calculators, medical instruments, credit card size devices, etc.
SR621SW battery is manufactured by most battery brands, often featuring similar labels, but also somewhat different discharge characteristics, leaving users wondering which battery is actually a good AG1/SR621SW battery equivalents.
Published: August 27, 2021.
SR621SW Battery Features and Specifications
SR621SW battery features physical dimensions of (D x H) 6.8 x 2.1 mm (~0.2677 x 0.0827 inches) and is based on the Silver Oxide chemistry - hence the "S" ("Silver") at the beginning of its label.
As such, the SR621SW battery features a nominal voltage of 1.55 volts, a cutoff voltage of 1.2 volts, and a nominal capacity in the 17-23 mAh range.
Actual capacity depends on the battery age, battery temperature, drain current, a number of previous current pulses, and similar.
Most common labels of the silver-oxide 6.8 x 2.1 mm batteries are SR621, SR621SW, SR621W, SR60, 164, 363, 364, SG1, AG1, etc. There are other labels in use as well, like Duracell D364 (hence the "D"), or Varta V 364 MF (hence the "V"), etc.
As one can see, silver-oxide SR621 batteries sometimes have letters "S" and "W" after the numbers, which means:
- letter 'S': the battery features sodium hydroxide electrolyte,
- letter 'W': the battery complies (or at least should comply) with the IEC 60086-3 watch batteries standard.
If the battery lacks these letters, it doesn't mean that it features potassium hydroxide electrolyte instead of sodium hydroxide electrolyte and it doesn't mean that the battery does NOT comply with the IEC 60086-3 watch batteries standard - it means that these letters are simply not part of the label and that the user should check the battery's datasheet in order to see actual discharge characteristics of the battery.
Most SR621SW batteries are designed for continuous low-discharge operation with good tolerance to pulse current, when required, making them suitable even for digital watches with alarms and small LED lights.
While silver-oxide chemistry is the most popular chemistry for 6.8 x 2.1 mm batteries, alkaline 6.8 x 2.1 mm batteries are also present on the market.
Alkaline 6.8 x 2.1 mm batteries are usually labeled as LR621, LR60, and sometimes AG1, although there are a few other, not so common, labels in use as well.
When compared to alkaline 6.8 x 2.1 mm batteries, silver-oxide 6.8 x 2.1 mm batteries feature lower self-discharge rates, have a larger capacity, and have a more stable output voltage.
The following comparison chart lists some of the most popular silver-oxide 6.8 x 2.1 mm batteries with their most important features:
|Battery||Nominal and Cutoff Voltages||Capacity||Operating Temperature||Annual Self-Discharge Rate||Discharge Current||Datasheet|
|Duracell D364||1.55V, 1.2V||20 mAh 68k1Ω down to 1.2V @20°C||0°C to +60°C||<10% @20°C||33.2μA @1.52V 68k1Ω @20°C||Duracell D364|
|Energizer 364/363||1.55V, 1.2V||19 mAh 68kΩ down to 1.2V @21°C||-||~2% @20°C||21μA @1.46V 68kΩ @21°C||Energizer 364/363|
|Maxell SR621SW||1.55V, 1.2V||18 mAh 47kΩ down to 1.2V @20°C||-10°C to +60°C||-||30μA @1.55V 47kΩ @20°C||-|
|muRata SR621||1.55V, 1.2V||20 mAh 47kΩ down to 1.2V @23°C||-10°C to +60°C||-||30μA @1.55V 47kΩ @23°C||muRata SR621|
|Seiko SR621SW||1.55V, 1.2V||23 mAh 30kΩ down to 1.2V @23°C||-10°C to +60°C||-||40μA||-|
|Varta V 364 MF||1.55V, 1.2V||17 mAh 68kΩ down to 1.2V @20°C||0°C to +60°C||<10% @20°C||~22μA @1.55V 68kΩ @20°C||-|
Note: We really don't know how the Duracell D364 battery is able to provide 33.2μA @1.52V over 68k1Ω @20°C - these values are from their PDF datasheet (last time we checked). While Duracell D364 is a very good battery, it can probably provide ~22μA in such conditions.
AG1/SR621SW Battery Safety Issues
AG1/SR621SW and all similar smallish batteries should be kept away from pets and kids - these small shiny objects can get swallowed easily.
Although modern batteries don't contain heavy metals like mercury and similar, when swallowed, they start electrolytic processes in the body that cause chemical burns.
While AG1/SR621SW batteries are relatively small and thus have relatively small capacity and voltage, they are really easily swallowed - that is why most AG1/SR621SW batteries come in so-called child-safe packages.
If AG1/SR621SW or any other similar battery gets swallowed, immediately contact the nearest emergency service and act according to their instructions.
Long Story Short: If You are looking for a 6.8 x 2.1 mm button/coin cell battery, go for an SR621SW battery from reputable brands that already have plenty of good reviews - such batteries have been tested by real users in the real-life situations and have passed with flying colors.
SR621SW batteries do cost slightly more than alkaline LR621, but they are worth the price difference. IMHO of course.