LR521, LR63, SR521, SR521S, SR521SW, SR63, 379, SG0, AG0 Battery Equivalents, and Replacements
LR521, SR521, 379, AG0 button cell batteries are often used in wrist watches, toys, remotes, and similar low drain devices.
These batteries are manufactured by most, if not all, most reputable battery brands and are easy to find if you know what to look for.
Updated: October 3, 2026.
SR521SW/379 Batteries Features and Specifications
SR521SW/379 button cell batteries feature physical dimensions of (D x H) 5.8 x 2.1 mm (0.2283 x 0.0827 inches).
Like most similar button cell batteries, SR521SW, 379, LR521, SR521, AG0 batteries feature two main chemistries - alkaline and silver oxide.
LR521 Battery Equivalent
Alkaline cells in this size family are commonly labeled LR521, LR63 or AG0. Check the chemistry and dimensions on the battery package rather than relying on a retailer’s list of replacement labels.
LR521/LR63/AG0 alkaline batteries have a nominal voltage of 1.5 V. Their voltage falls during discharge. Usable capacity depends on the load, temperature and the minimum voltage at which the device can operate.
The typical capacity of alkaline 379 battery is around 10 mAh, also depending on the common temperature, drain current, battery age, and similar.
Some of the most popular LR521 battery models on the market include (Amazon links, the links open in the new windows):
SR521SW (379) Battery Equivalent
Silver-oxide 5.8 x 2.1 mm batteries are commonly labeled as SR521, SR521, SR521SW, SR63, 379, SG0, and similar.
These batteries differ from alkaline batteries by mostly having the prefix 'SR', although some brands use 'numbers only' labels and similar. In order to attract potential customers, most of the brands write down the labels of the models that their batteries actually replace.
Of course, this sometimes increases the confusion about which battery to buy, but generally greatly simplifies finding proper battery replacement.
The nominal voltage of SR521SW/379 batteries is 1.55 volts and the typical capacity is in the 15-18 mAh range, which is significantly more than the alkaline typical capacity of 10 mAh.
The cut-off voltage of silver-oxide batteries is ~1.2 volts, but this also depends on the cut-off voltage of the device in use.
In any case, silver-oxide batteries have much more stable voltage than alkaline batteries, they have a larger capacity and longer shelf life.
Some of the most popular SR521SW battery models on the market include (Amazon links, the links open in the new windows):
SR521SW/379 Batteries Comparison Chart
The following chart lists some of the most popular SR521/379 batteries with their most important features and specifications:
| Battery Datasheet | Chemistry Nominal and Cutoff Voltages |
Capacity Discharge Current |
Operating Temperature Annual Self-Discharge Rate |
| Duracell D379 | Silver Oxide 1.55V, 1.2V |
16 mAh, 68kΩ @20°C down to 1.2V 22 μA |
0°C to +60°C ≤10% @20°C |
| Energizer 379 | Silver Oxide 1.55V, 1.2V |
18 mAh, 68kΩ @21°C down to 1.2V 22 μA, @1.52V @21°C over 68kΩ |
- ≤3% @20°C |
| Renata SR521SW | Silver Oxide 1.55V, 1.2V |
16 mAh, 47kΩ @20°C down to 1.2V 32.6 μA, over 47kΩ @20°C |
-10°C to +60°C ≤5% @20°C |
| Varta SR521SW | Silver Oxide 1.55V, 1.2V |
15 mAh, 68kΩ @20°C down to 1.2V - |
0°C to +60°C - |
As one can see, the most popular button/coin 5.8x2.1 mm cells are silver-oxide batteries featuring a nominal voltage of 1.55V and cutoff voltage of 1.2V.
However, actual capacity depends on the temperature, battery age, and discharge conditions, but on average, it is in the 15-18 mAh range.
How long do SR521SW and 379 batteries typically last?
SR521SW and 379 batteries typically last 1 to 3 years, depending on the device and usage patterns.
These silver oxide batteries are designed for low-drain applications, such as watches and small electronics, where they can provide a stable, continuous output over a long period.
Factors like device power consumption, environmental conditions, and storage can impact battery life.
In devices with low power demands, such as analog watches, they may last closer to 3 years, while high-drain applications may reduce their lifespan to around 1 year.
Are There Rechargeable Versions of SR521SW and 379 Batteries?
No, there are typically no rechargeable versions of SR521SW and 379 batteries.
These batteries are small, silver oxide button cells designed for low-drain applications, like watches, calculators, and small electronic devices, where a long-lasting, stable power output is needed.
Silver oxide chemistry does not generally support recharging, and attempting to recharge these batteries can be dangerous and may cause leakage or rupture.
For applications requiring rechargeable options, consider devices that can use lithium coin cells or other rechargeable battery types designed specifically for recharging.
SR521SW/379 Batteries Safety Issues
Keep new and used button batteries out of reach of children and pets. If a button battery is swallowed or ingestion is suspected, seek immediate medical attention. Do not induce vomiting.
SR521SW/379 Batteries Frequently Asked Questions (FAQ)
Here are some of the most common Frequently Asked Questions about SR521SW/379 batteries and button/coin cell batteries in general:
What are 379 batteries used for?
SR521SW/379 batteries are used in wrist watches, calculators, medical equipment (thermometers, glucose meters, and similar), remote control fobs, micro LED flashlights, some laser pointers, and similar.
What battery replaces SR521SW?
For a device specifying SR521SW, choose a compatible 379/SR521SW silver-oxide cell with a nominal voltage of 1.55 V. Confirm its dimensions and compatibility with the device specification. Alkaline LR521/LR63/AG0 cells have a similar size but different voltage and discharge characteristics; use them only if the device manufacturer permits that substitution.
Is 377 battery the same as 379?
No, 379 batteries feature physical dimensions of 5.8 x 2.1 mm, and 377 batteries feature physical dimensions of 6.8 x 2.6 mm.
What is the smallest size watch battery?
One very small watch-battery size is SR416SW/337, commonly described as approximately 4.8 x 1.6 mm, or 0.1890 x 0.0630 inches. Exact dimensions and tolerances depend on the product datasheet.
Are button batteries toxic?
Button batteries can cause serious internal injury if swallowed. Mercury-free labeling does not make ingestion safe. If a button battery is swallowed or ingestion is suspected, seek immediate medical attention. Do not induce vomiting.
Long Story Short: if you need a button cell battery 5.8 mm in diameter and 2.1 mm in height and you are not sure which one to get, follow these rules:
- LR521, LR63, AG0 and similar are alkaline batteries: cheaper, but also less stable voltage and lower capacity,
- SR521, SR521S, SR521SW, SR63, 379, SG0 and similar are silver-oxide batteries: they cost slightly more, but have more stable voltage and higher capacity. Also, their shelf life is longer.
If you have wrist watch or any similar electronic device, be sure to get a battery that is labeled SR521SW and/or 379. Personally, the price difference between alkaline and silver oxide batteries is very low and performances of silver-oxide batteries, IMHO, justify buying silver-oxide batteries.
Thus, if you are looking for new SR521SW (379) battery, for the most up-to-date offers and prices, feel free to check the following links (Amazon links, the links open in the new windows):
With quick delivery, you can have new SR521SW/379 batteries very quickly.