AG4, SR626SW, LR626, LR66 Battery Equivalents Leave a comment

AG4, LR626 and LR66 are alkaline button batteries with identical dimensions and specs. They are a very common button battery used for consumer electronics and are not rechargeable. The silver oxide equivalent is the SR626SW and SR626. Most typical use of an AG4 battery is as a wrist watch replacement battery. In this article we will discuss the many different chemistries that this battery is available in including alkaline, Zinc air and silver oxide.

AG4 Battery Pack of 10 Alkaline 1.5V
AG4 Battery Pack of 10 Alkaline 1.5V Button Cell


Alkaline AG4 Battery Equivalents and Specifications

  • Equivalents: AG4, LR626, LR66, L626
  • Type: Alkaline
  • Diameter: 6.8 mm
  • Thickness: 2.6 mm
  • Capacity: 18mAh
  • Voltage: 1.5 volts
  • Weight: 0.3-0.5 grams

AG4 batteries have a chemistry that is alkaline and should not be used as a watch battery replacement or a hearing aid battery replacement. The alkaline AG4 will not have enough capacity or continuous voltage to power these devices. An alkaline batteries voltage will slowly drop over time. It is imperative that the correct chemistry battery is used for the right application.


Silver Oxide SR626SW Battery Equivalents and Specifications

  • Equivalents: SR626, SR626SW, SR626W, SR66, SR66SW, SR628SW, SR6265W, SR66SW, SR625SW, CR626SW, 1176SO, 177, 376, 377, 377A, 377X, 377BA, E377, E377A, E377CA, , 377S, V377, D377, 280-39, 626, 606, 626A, A1398
  • Type: Silver Oxide
  • Diameter: 6.8 mm
  • Thickness: 2.6 mm
  • Capacity: 26mAh – 32mAh
  • Voltage: 1.55 volts
  • Weight: 0.6-0.7 grams

SR626SW batteries and their equivalents are used to power modern wristwatches. They can be used as a replacement for the AG4 alkaline battery but doing so is not cost effective. The silver oxide version is preferable for keeping time in clocks and watches as the continuous voltage of 1.55V is maintained throughout the life of the battery. A silver oxide battery will maintain voltage over time whereas the alkaline battery voltage will lower over time and not maintain 1.55V.


AG4 Battery Information

Batteries starting with the SR designation are of silver-oxide chemistry (SR626, SR66, SR626SW etc). If the battery starts with AG or LR designation then it is an alkaline composition. This rule doesn’t always hold true as many manufacturers designate their own labels. Batteries ending with the digit ‘W’ are in compliance with IEC 60086-3 watch batteries standard. Manufacturers will label their batteries with a W to indicate they are for watch usage (silver oxide). Watch batteries also have numbers to indicate their usage. For instance the 377 battery is a high drain non rechargeable silver oxide battery and the 376 is a low drain silver oxide battery. Silver oxide batteries maintain a stable 1.55V throughout their life whereas the alkaline equivalent voltage will lower over time.


SR621SW vs SR626SW Battery

The SR621SW battery and the SR621SW battery are both silver oxide but are not compatible. The 6 indicates a standard diameter of 6.8mm but the 21 and 26 indicate a different height. 2.1mm and 2.6mm respectively. Although this may seem insignificant, it is a very big difference inside a tiny watch compartment. A loose battery that is not making contact with the electronics is not a very good timepiece.

SR621SW Battery Specifications

  • Diameter: 6.8mm
  • Height: 2.1 mm
  • Voltage: 1.55V
  • Capacity: 18mAh – 23mAh

SR626SW Battery Specifications

  • Diameter: 6.8mm
  • Height: 2.6 mm
  • Voltage: 1.55V
  • Capacity: 24mAh – 28mAh


AG4 and SR626SW Battery Questions FAQ

What is an equivalent SR626SW battery?

The alkaline equivalent is AG4 or LR626.

Is a 377 battery the same as a 376 battery?

The 377 and 376 battery are identical and have the same dimensions of 6.8mm x 2.6mm. The 376 is a high drain silver oxide battery whereas the 377 is a low drain silver oxide battery.

What replaces a SR626 watch battery?

Any of the equivalent batteries listed that have dimensions of 6.8 x 2.6 mm including the alkaline AG4 and SR626SW battery.

What is an SR626SW battery?

An SR626SW battery is a silver-oxide non rechargeable button battery with dimensions of 6.8mm x 2.6 mm cell using a chemistry of sodium hydroxide electrolyte.

Is an Energizer 377 the same as an SR626SW?

Yes, an Energizer 377 or 376 battery is a silver oxide battery measuring 6.8mm x 2.6 mm. It is equivalent to a SR626SW battery.

What does SW mean on a battery?

The battery code after the digits containing ‘SW’ indicates the battery is made of sodium hydroxide electrolyte and is in compliance with the watch battery standard of IEC 60086-3.


AG4 Battery Safety Information

Batteries made in the last several decades have not used mercury or cadmium or dangerous and unstable heavy metals. Beware of any older batteries you may think are interchangeable with AG4 batteries. If the battery designation starts with ‘MR’ it may be made from mercury. Dispose of these batteries properly.

Keep all small batteries out of reach of children. AG4 batteries are particularly small and must be kept in a safe place. Proper storage conditions for an AG4 battery consist of a dry cool environment.

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