AG4, LR626, LR66, 177/376/377, SR626, SR626SW Battery Comphrehensive Knowledge

AG4, LR626, LR66, 177/376/377, SR626, and SR626SW batteries are very popular


AG4, LR626, LR66, 177/376/377, SR626, and SR626SW batteries are widely-used non-rechargeable button/coin cell batteries, offered in various chemistries by numerous battery manufacturers.

They are frequently utilized in wristwatches, calculators, and similar compact electronic devices that demand dependable power sources.

AG4, LR626, LR66, 177/376/377, SR626, and SR626SW batteries are very popular

SR626SW, LR626, 377, AG4 Battery Details

SR626SW/LR626 batteries are characterized by their dimensions of 2.6 x 6.8 mm (~0.1023 x 0.2677 inches).

As per the IEC standard, these batteries may be labeled LR626 (alkaline) or SR626 (silver-oxide), while the ANSI standard denotes them as 1176SO batteries. Alternatively, shorter two-digit codes LR66 and SR66 are also used.

Manufacturers often assign their own labels to these batteries, but they typically include information about the chemistry, nominal voltage, battery equivalents, and other standard codes.

The capacities of LR626 (alkaline) or SR626 (silver-oxide) batteries vary depending on the chemistry and the cutoff voltage of the device they power. Alkaline batteries experience a rapid voltage drop, making them less suitable for devices like wristwatches.

Given their small size, these batteries are generally affordable. In summary, when in need of an LR626/SR626 wristwatch battery, opt for an SR626 or SR626SW variant.

Few notes:

AG4 should be alkaline G4 battery

AG4 and SG4 batteries typically denote ‘alkaline G4’ and ‘silver-oxide G4’ respectively. However, manufacturers sometimes mark silver-oxide batteries with both SG4 and AG4 to indicate compatibility with AG4/SG4/LR66/SR66/LR626/SR626/SR626SW batteries.

Here’s a guide to interpreting battery codes:

  • If the code begins with ‘L’, it indicates an alkaline R626 battery (e.g., LR626, LR66, AG4).
  • If it starts with ‘S’, it’s a silver-oxide R626 coin cell (e.g., SR626, SR66, SR626SW).
  • ‘P’ in the code signifies potassium hydroxide electrolyte.
  • ‘S’ indicates sodium hydroxide electrolyte.
  • Absence of ‘P’ or ‘S’ suggests organic electrolyte, although some manufacturers omit these letters in labeling.
  • ‘W’ in the code complies with the IEC 60086-3 watch batteries standard, commonly seen in silver-oxide batteries labeled as SR626SW for wristwatches.
  • Numeric labels like 376 and 377 denote non-rechargeable silver-oxide batteries, with 376 being high-drain and 377 low-drain. Modern versions of these batteries offer stable output voltage, with 376 having better high-drain tolerance and 377 featuring lower self-discharge rates.

To address confusion and leverage advancements in battery technology, some manufacturers offer multi-drain 376/377 batteries compatible with SR626SW, featuring robust high-drain current tolerance and low self-discharge rates.

376 377 battery

 LR626 vs. SR626 Batteries Comparison Chart

The following chart provides a comparison and examples of alkaline and silver-oxide 6.8 x 2.6 mm coin-cell batteries, specifically in the context of replacing SR626SW watch batteries.

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

LR626/SR626 batteries are available in two distinct chemistries:

  • Alkaline LR66/LR626 batteries have a nominal voltage of 1.5 volts, which decreases relatively quickly over time to 1.0 volts. This voltage drop may pose reliability issues for sensitive electronics when using alkaline AG4/LR66/LR626 batteries. Additionally, their capacity when drained to 1.0 volts is approximately 30% lower compared to silver-oxide batteries and up to 50% lower when drained to 1.2 volts.
  • Silver-oxide SR626/SR626SW batteries maintain a nominal voltage of 1.55 volts, remaining relatively constant throughout their discharge cycle. These batteries boast a larger capacity, offering extended operating times for various devices with a single battery replacement.

It’s important to note that some silver oxide SR626 batteries are designed as high-drain, suitable for digital watches and similar electronics, while others are intended as low-drain, ideal for analog watches, digital watches without alarms and LEDs, thermometers, etc. However, many manufacturers now offer 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

The following cross-reference chart presents key features and specifications of some of the most popular SR626, 377, and 376 battery models.


Nominal and Cutoff Voltages


Discharge Current

Operating Temperature

Annual Self-Discharge Rate

Duracell D377/376 Silver Oxide


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


24 mAh, 47kΩ down to 1.2V @21°C

31μA @1.46V 47kΩ @21°C

~2% @20°C

muRata SR626 Silver Oxide


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


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


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


21 mAh, 47kΩ down to 1.2V @20°C

0°C to +60°C

<10% @20°C

As evident, actual performances of these batteries vary based on factors such as discharge current, temperature, and battery age.

It’s worth noting that these examples represent only a selection of the most commonly used silver-oxide 6.8 x 2.6 mm button/coin cells available in the market.

SR626SW vs. SR621SW Batteries

Both SR626SW and SR621SW batteries are silver-oxide non-rechargeable cells designed for powering wristwatches and other delicate electronic devices.

SR626SW vs. SR621SW Batteries

The primary distinction between these two batteries lies in their size and discharge characteristics:

  • SR626SW battery: Dimensions (D x H) 6.8 x 2.6 mm, nominal voltage 1.55V, capacity 25-27 mAh.
  • SR621SW battery: Dimensions (D x H) 6.8 x 2.1 mm, nominal voltage 1.55V, capacity 18-23 mAh.

While the height difference between SR626SW and SR621SW batteries is just 0.5 mm, it can have implications for compatibility. While battery compartments designed for SR626SW batteries may accommodate smaller SR621SW batteries, the contacts with the SR621SW battery may not be entirely reliable.

Conversely, compartments intended for SR621SW batteries may not accept SR626SW batteries at all, or they may become deformed.

In summary, if you require an SR626SW battery, it’s advisable to choose a silver-oxide 6.8 x 2.6 mm battery from reputable brands.

LR626/SR626 Batteries Safety Issues

Modern LR626/SR626 batteries are free from mercury, cadmium, and other heavy metals or harmful toxins. However, due to their small size and shiny appearance, they may attract children and pets, increasing the risk of accidental ingestion.

If swallowed, these batteries can initiate electrolytic reactions within the body, leading to chemical burns, which pose significant dangers. Despite their relatively low voltage of around 1.5V, swift action is crucial in such situations.

In the event of ingestion, it’s imperative to promptly contact the nearest emergency center and follow their instructions to ensure appropriate medical attention is provided.

LR626/SR626SW Batteries Frequently Asked Questions – LR626/SR626SW FAQ

Here are some frequently 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, conforming to the IEC 60086-3 watch batteries standard. Most multi-drain 376/377 and SR626 batteries are designed for wristwatches, making it relatively easy to find a 6.8 x 2.6 mm battery labeled as “SR626SW.”

Is 377 battery the same as SR626SW?

While 377 and SR626SW batteries share the same physical dimensions and likely the same chemistry, they are not necessarily identical.

What replaces a 626 watch battery?

A “626” watch battery, with dimensions of 6.8 x 2.6 mm, can be replaced with SR626W, SR626SW, 376, 377, or 376/377 batteries.

What is an SR626SW battery?

An SR626SW battery is a non-rechargeable silver-oxide button/coin cell, 6.8 x 2.6 mm in size, containing sodium hydroxide electrolyte, and complying with the IEC 60086-3 watch batteries standard.

What Duracell battery replaces SR626SW?

Duracell manufactures the D377/376 battery, which is equivalent to most SR626SW batteries.

Are 626 and 377 batteries equivalent?

If the 626 battery is silver-oxide, then they are generally compatible, although there may be some differences.

Are 357 and 377 batteries the same?

No, they differ in size, capacity, and other important features.

Are 377 and 392 batteries interchangeable?

No, they have different physical dimensions.

Can I use a 364 battery instead of a 377?

While some devices may accept both, compatibility issues with contacts are possible.

What battery is smaller than a 377?

Batteries smaller than 377 include SR416SW, SR512SW, SR516SW, SR521SW, SR527SW, SR616SW, and SR621SW.

What does SW mean on a battery?

“SW” indicates the battery complies with the IEC 60086-3 watch batteries standard.

How do you know which battery to buy for a watch?

Check the watch documentation or manufacturer’s website, or search online using the watch’s name/label + “battery.”

How to replace the SR626SW watch battery?

It’s advisable to have a watchmaker replace the battery, as they can check for other worn parts. However, it can also be done at home if confident in spotting and replacing worn parts.

Where to buy watch battery SR626SW?

SR626SW batteries are available in hardware stores, office supply stores, and online shops.

What “CR” battery is equivalent to an SR626SW battery?

No “CR” battery is equivalent, as “CR” batteries are 3.0V lithium manganese dioxide batteries, while SR626SW batteries are 1.55V silver-oxide batteries.


If you require a replacement for your analog or digital watch, thermometer, calculator, pager, toy, micro-LED flashlight, or similar electronic device, opt for a high-quality SR626SW (376/377) battery from reputable brands with positive reviews.

If you’re uncertain about low-drain or high-drain models, consider a multi-drain SR626SW battery, also labeled as a 367/377 battery.