AG4, LR626, LR66, 177/376/377, SR626, and SR626SW batteries are very popular non-rechargeable button/coin cell batteries, available in several chemistries and manufactured by practically all battery brands.
These batteries are commonly found in wrist watches, calculators, and similar small electronic devices requiring a reliable power source.
Updated: September 23, 2022.
SR626SW, LR626, 377, AG4 Battery Features and Specifications
SR626SW/LR626 batteries feature a physical dimensions of (DxH) of 2.6 x 6.8 mm (~0.1023 x 0.2677 inches).
According to the IEC standard, and depending on their chemistry, these batteries should be labeled LR626 (alkaline) or SR626 (silver-oxide) batteries, and according to the ANSI standard, 1176SO batteries.
Sometimes shorter, two-digit code is used: LR66 for alkaline and SR66 for silver-oxide batteries.
Many manufacturers use their own labels for these batteries, but they also tend to add IEC and other standard codes, including short descriptions about the chemistry, nominal voltage, battery equivalents, and similar.
LR626 (alkaline) or SR626 (silver-oxide) capacities depend on the chemistry, but also on the cut-off voltage of the used device - alkaline batteries' voltage quickly drops, making them not so suitable for electronic devices like wrist watches and similar.
Since these batteries are rather small, so is their price per individual battery. In short, if you need LR626/SR626 wrist watch battery, go for an SR626 or SR626SW battery.
Few notes:
- AG4 vs SG4: AG4 should be 'alkaline G4' and SG4 should be 'silver-oxide G4' battery. However, sometimes manufacturers mark silver-oxide batteries with both SG4 (correct) and AG4 (not correct) to emphasize that their battery is a replacement for AG4/SG4/LR66/SR66/LR626/SR626/SR626SW battery.
- if the battery code starts with the 'L', then it should be an alkaline R626 battery (LR626, LR66, AG4),
- if the battery code starts with the 'S', then it is a 'silver-oxide' R626 coin cell (SR626, SR66, SR626SW).
- if the battery code after the digits contains 'P', then it is the battery with potassium hydroxide electrolyte.
- if the battery code after the digits contains 'S', then it is the battery with sodium hydroxide electrolyte.
- if the battery code after the digits doesn't contain 'P' or 'S', then probably that battery contains organic electrolyte - we emphasize 'probably' because some manufacturers simply drop out these letters when labeling their batteries.
- if the battery code after the digits contains 'W', then the battery complies with the IEC 60086-3 watch batteries standard - most manufacturers of '626' batteries label their silver-oxide batteries as SR626SW to emphasize that these batteries are silver-oxide batteries for wrist watches - and if they are good for wrist watches, then they are good for other electronic devices, too.
- some manufacturers use number labels, like 376 and 377. Generally speaking, the 376 battery is a non-rechargeable silver-oxide high-drain battery, while the 377 battery is a non-rechargeable silver-oxide low-drain battery.
Modern 376 and 377 are suitable as wrist watch batteries since they feature stable output voltage. However, 376 batteries feature better high-drain current tolerance, while 377 batteries feature a lower self-discharge rate.
To prevent confusion and thanks to modern chemistry and battery technology, some manufacturers offer multi-drain 376/377 batteries (compatible with SR626SW batteries, of course) that feature good tolerance to high-drain pulse currents and low self-discharge rate.
LR626 vs. SR626 Batteries Comparison Chart
Comparison and examples of alkaline and silver-oxide 6.8 x 2.6 mm coin-cell batteries are given in the following SR626SW watch battery replacement chart:
| Chemistry | Alkaline | Silver-Oxide |
| Nominal Voltage | 1.5V | 1.55V |
| End-Point Voltage | 1.0V | 1.2V |
| Notes | Voltage drops over time | Very constant voltage |
| Typical Labels | LR66, LR626, AG4 | 177, 376, 377, AG4, SG4, SR66, SR626, SR626SW |
| Typical Capacity | 15-17 mAh | 25-27 mAh |
As one can see, LR626/SR626 batteries are available in two different chemistries:
- Alkaline LR66/LR626 batteries have a nominal voltage of 1.5 volts, and it relatively quickly drops over time down to 1.0 volts.
Since sensitive electronics might have issues operating at such low voltage and may have issues with reliability when using alkaline AG4/LR66/LR626 batteries.
Also, their capacity when drained down to 1.0 volts is lower when compared with silver-oxide batteries by some 30% and up to 50% lower when drained down to 1.2 volts.
- Silver-oxide SR626/SR626SW batteries have a nominal voltage of 1.55 volts, and it is rather constant over time as the battery is drained. Also, these batteries have a larger capacity providing a much longer operating time for various devices using a single battery replacement.
Note that some silver oxide SR626 batteries are designed as high-drain batteries and are more suitable for digital watches and similar electronic devices, while other SR626 batteries are designed as low-drain batteries and are more suitable for analog watches, digital watches without alarms and LEDs, thermometers, and similar.
But, most manufacturers today offer so-called multi-drain 376/377 (SR626SW) batteries, suitable for both digital and analog watches, toys, thermometers, keychain LED flashlights, and similar devices.
SR626SW, 377, 376 Batteries Comparison Chart
The following cross-reference chart lists some of the most popular SR626, 377, and 376 battery models, with their most important features and specifications:
Battery Datasheet | Chemistry Nominal and Cutoff Voltages | Capacity Discharge Current | Operating Temperature Annual Self-Discharge Rate |
| Duracell D377/376 | Silver Oxide 1.55V/1.2V | 24 mAh, 47kΩ down to 1.2V @20°C 44.8μA @1.54V @20°C | 0°C to +60°C <10% @20°C |
| Energizer 377/376 | Silver Oxide 1.55V/1.2V | 24 mAh, 47kΩ down to 1.2V @21°C 31μA @1.46V 47kΩ @21°C | - ~2% @20°C |
| muRata SR626 | Silver Oxide 1.55V/1.2V | 28 mAh, 30kΩ down to 1.2V @23°C 50μA @1.55V 30kΩ @23°C | -10°C to +60°C - |
| Renata 376 High Drain | Silver Oxide 1.55V/1.2V | 27 mAh, 34k8Ω down to 1.2V @20°C 44.5μA @1.55V 34k8Ω @20°C | -10°C to +60°C <10% @20°C |
| Renata 377 Low Drain | Silver Oxide 1.55V/1.2V | 24 mAh, 34k8Ω down to 0.9V @20°C 43.7μA @1.55V 34k8Ω @20°C | -10°C to +60°C <5% @20°C |
| Varta V 377 MF | Silver Oxide 1.55V/1.2V | 21 mAh, 47kΩ down to 1.2V @20°C - | 0°C to +60°C <10% @20°C |
As one can see, actual performances vary depending on the discharge current and temperature but also depending on the battery age.
Of course, these are just some of the most popular silver-oxide 6.8 x 2.6 mm button/coin cells on the market.
SR626SW vs. SR621SW Batteries
Both SR626SW and SR621SW batteries are silver-oxide non-rechargeable batteries suitable for powering wrist watches and other sensitive electronic devices.
The main difference between these two batteries is their size and hence discharge characteristics:
- SR626SW battery: (D x H) 6.8 x 2.6 mm, 1.55V, 25-27 mAh
- SR621SW battery: (D x H) 6.8 x 2.1 mm, 1.55V, 18-23 mAh.
The height difference of the SR626SW and SR621SW batteries is just 0.5 mm, which isn't much - however, while battery compartments intended for SR626SW batteries may accept smaller SR621SW batteries, contacts with the SR621SW battery may NOT be fully reliable.
On the other hand, the battery compartment intended for the SR621SW battery may not accept at all SR626SW battery, or it may deform.
In short, if You do need an SR626SW battery, go for a silver-oxide 6.8 x 2.6 mm battery from reputable brands.
LR626/SR626 Batteries Safety Issues
Modern LR626/SR626 batteries don't contain mercury, cadmium, and other heavy metals or dangerous toxins.
However, these batteries are 'small shiny objects' that may attract kids and pets, and due to their dimensions, these batteries are easily swallowed.
If they get swallowed, these batteries may start electrolytic reactions that may cause chemical burns, which are very dangerous.
Although these batteries don't have a 'large' capacity and are just ~1.5V, if they get swallowed, be sure to immediately contact the nearest emergency center and act according to their instructions.
LR626/SR626SW Batteries Frequently Asked Questions - LR626/SR626SW FAQ
Here are some of the most commonly asked questions about alkaline and silver-oxide 6.8 x 2.6 mm batteries:
What battery is equivalent to SR626SW?
SR626SW battery is a 6.8 x 2.6 mm silver-oxide battery with sodium hydroxide electrolyte which complies with the IEC 60086-3 watch batteries standard.
Since most multi-drain 376/377 and SR626 batteries are designed as wrist watch batteries, it shouldn't be too hard to find a 6.8 x 2.6 mm battery that also comes with a label of "SR626SW" battery.
Is 377 battery the same as SR626SW?
377 battery and SR626SW battery share the same physical dimensions of 6.8 x 2.6 mm, and probably the same battery chemistry.
However, although these batteries are compatible with most applications, they are not necessarily "exactly the same" batteries.
What replaces a 626 watch battery?
The proper label of the "626" battery should be either LR626 or SR626(SW) battery - a "626" 6.8 x 2.6 mm watch battery may be replaced with a 6.8 x 2.6 mm SR626W, SR626SW, 376, 377, and 376/377 battery.
What is an SR626SW battery?
SR626SW battery is a non-rechargeable silver-oxide button/coin 6.8 x 2.6 mm cell with sodium hydroxide electrolyte and it complies with the IEC 60086-3 watch batteries standard.
What Duracell battery replaces SR626SW?
Duracell manufacturers D377/376 6.8 x 2.6 mm battery which is equivalent to most SR626SW batteries.
Is Energizer 377 the same as SR626SW?
Yes, Energizer 377/376 battery is a 6.8 x 2.6 mm battery based on the silver-oxide chemistry which is equivalent to most SR626SW batteries.
Are 626 and 377 batteries equivalent?
If the 626 battery is a silver-oxide battery, then yes, 626 and 377 batteries are more or less compatible batteries. We say "more or less" since these batteries may differ in a few other important details as well.
Are 357 and 377 batteries the same?
357 batteries are 11.6 x 5.4 mm batteries, while 377 batteries are 6.8 x 2.6 mm batteries - they differ in size, capacity, and other important features making them anything but compatible.
Are 377 and 392 batteries interchangeable?
377 batteries feature physical dimensions of 6.8 x 2.6 mm, while 392 batteries feature physical dimensions of 7.9 x 3.6 mm, so no, they are not interchangeable.
Can I use a 364 battery instead of a 377?
364 battery features physical dimensions of 6.8 x 2.1 mm (lust as SR621SW battery), and it is generally not compatible with 377 battery with physical dimensions of 6.8 x 2.6 mm.
Some watches and other similar devices that accept 377 batteries may also function properly with 364 batteries (and vice versa), but issues with contacts are also possible.
What battery is smaller than a 377?
SR416SW battery (4.8 x 1.6 mm), SR512SW (5.8 x 1.3 mm), SR516SW (5.8 x 1.6 mm), SR521SW (5.8 x 2.1 mm), SR527SW (5.8 x 2.7 mm), SR616SW (6.8 x 1.65 mm) and SR621SW (6.8 x 2.1 mm) batteries are smaller than 377 battery.
What does SW mean on a battery?
If the battery code after the digits contains 'S', then it is the battery with sodium hydroxide electrolyte, and if the battery code after the digits contains 'W', then the battery complies with the IEC 60086-3 watch batteries standard.
Also, most manufacturers of '626' batteries label their silver-oxide batteries as SR626SW to emphasize that these batteries are silver-oxide batteries for wrist watches - and if they are good for wrist watches, then they are good for other electronic devices, too.
How do you know which battery to buy for a watch?
Check the documentation of your watch, or check the official website of the watch manufacturer, use the search option (if available) and look for the watch documentation or ask for their support.
Also, check on the Google "watch name/label" + "battery".
How to replace the SR626SW watch battery?
The easiest but not the cheapest way of replacing SR626SW or any similar watch battery is to let the watchmaker do the job - the watch is carefully opened using special tools, the battery is located and replaced with the new one, and the watch is properly closed.
However, while replacing the battery, the watchmaker may check other watch parts, and if the wear is noticed, they can also be replaced.
Obviously, the battery can be replaced at home. However, ask yourself if You can spot and replace worn parts of your watch.
Where to buy watch battery SR626SW?
SR626SW watch battery can be purchased in most hardware or even office stores, or the battery can be ordered from online shops.
What "CR" battery is equivalent to an SR626SW battery?
No "CR" battery is equivalent to an SR626SW battery - "CR" batteries are non-rechargeable 3.0V lithium manganese dioxide batteries, while SR626SW batteries are non-rechargeable 1.55V silver-oxide batteries.
For short: if you need a 6.8 x 2.6 mm button/coin cell battery replacement for your analog or digital watch, thermometer, calculator, pager, toy, micro-LED flashlight, or similar electronic device, go for a high-quality SR626SW (376/377) battery from reputable brands which has many positive reviews.
If You are unsure regarding low-drain or high-drain models, go for a multi-drain SR626SW battery, also labeled as 367/377 battery.
For the most up-to-date offers and prices, feel free to check the following Amazon links:
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As an enthusiast deeply immersed in the world of button/coin cell batteries, particularly the AG4, LR626, LR66, 177/376/377, SR626, and SR626SW, I bring a wealth of firsthand knowledge to shed light on these miniature power sources. My expertise stems from an extensive exploration of various chemistries, manufacturing practices, and applications in small electronic devices.
The article provides a comprehensive overview of these non-rechargeable batteries, emphasizing their prevalence in wristwatches, calculators, and similar gadgets. Notably, the dimensions of SR626SW/LR626 batteries (2.6 x 6.8 mm) are highlighted, conforming to IEC and ANSI standards. The piece delves into the nuances of labeling, with variations like LR66 for alkaline and SR66 for silver-oxide, reflecting the diverse approaches adopted by manufacturers.
Crucially, the comparison between alkaline LR626 and silver-oxide SR626 batteries is elucidated through a detailed chart, emphasizing differences in nominal voltage, end-point voltage, and capacity. The impact of discharge characteristics on electronic devices is also addressed, underlining the suitability of silver-oxide batteries for prolonged usage.
The article doesn't merely stop at theoretical distinctions; it delves into practical considerations with a comparison chart featuring popular SR626, 377, and 376 battery models. Specifications such as chemistry, nominal and cutoff voltages, capacity, discharge current, operating temperature, and annual self-discharge rate are meticulously presented, offering a practical guide for consumers.
Moreover, the differentiation between SR626SW and SR621SW batteries is explored, emphasizing the size disparity and potential compatibility issues. Safety concerns related to the ingestion of these small batteries are addressed, highlighting the electrolytic reactions that could cause chemical burns.
The inclusion of a comprehensive FAQ section further enhances the reader's understanding, covering topics like battery equivalence, compatibility, and replacement. Notably, the article provides valuable insights into the intricacies of battery codes, electrolyte types, and watch battery standards (IEC 60086-3).
To conclude, this article serves as a go-to resource for anyone seeking clarity on AG4, LR626, LR66, 177/376/377, SR626, and SR626SW batteries. Its blend of theoretical knowledge, practical comparisons, and safety considerations establishes it as a comprehensive guide for both enthusiasts and those seeking practical advice on battery selection and usage.
