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Canonical battery record · checked 2 September 2026

SR621W

The SR621W silver-oxide family is 6.8 × 2.15 mm. Preserve the W/SW drain designation unless current device or manufacturer guidance permits otherwise.

SR621W
Answer

SR621W is the supported canonical designation for one 6.8 × 2.15 mm silver-oxide watch cell. No other family is treated as an automatic replacement.

Top profile · Ø 6.8 mm
Side profile · 2.15 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
Format
Silver-oxide watch cell
Dimensions
6.8 × 2.15 mm
Voltage
1.55 V nominal
Chemistry
Silver oxide / zinc
Drain context
W: higher-drain profile
Rechargeable?
No — primary cell; do not recharge.
Capacity context
Manufacturer- and test-condition-specific; no universal capacity is asserted from the selection guide.
Confidence
High

Equivalence and confusion matrix

Code or familyClassificationReason
SR621WExact equivalentThese evidence-backed markings resolve to this one canonical record and share its cited physical and electrical specification.
SR621SW / 364Conditional substituteBoth are 6.8 × 2.15 mm silver oxide / zinc cells at 1.55 V nominal, but their drain designations differ (W: higher-drain profile versus SW: low-drain profile). Preserve the device-specified class.
LR621 / AG1Same size, different electrical familyThe 6.8 × 2.15 mm envelope matches, but the electrical families do not: Silver oxide / zinc at 1.55 V nominal versus Alkaline manganese dioxide / zinc at 1.5 V nominal. Physical fit is not equivalence.
LR626 / AG4Not equivalentThe physical envelopes differ (6.8 × 2.15 mm versus 6.8 × 2.6 mm). Do not force, stack or infer equivalence from a shared diameter or code pattern.
SR626SW / 377Not equivalentThe physical envelopes differ (6.8 × 2.15 mm versus 6.8 × 2.6 mm). Do not force, stack or infer equivalence from a shared diameter or code pattern.

Supported application context

  • Watches specifying this exact code and drain class

Application context is limited to the scope stated in Maxell Button and Coin Battery Cross-reference Table; it is not a device compatibility claim.

This record belongs to the watch-cell system. Maker numbers are useful aliases, while the W higher-drain designation remains part of device selection.

SR621W is the higher-drain member of the 6.8 × 2.15 mm silver-oxide pair. SR621SW/364 shares the physical envelope, nominal voltage and chemistry while retaining the low-drain SW designation.

What the code means

SR621W identifies a silver-oxide watch cell. The W or SW suffix is part of the supported identity and records the manufacturer drain class.

Discharge and drain behaviour

Silver-oxide cells are selected for a comparatively stable working voltage. W: higher-drain profile remains material in watch applications, so a shared diameter and height do not erase the W/SW distinction.

Capacity context: Manufacturer- and test-condition-specific; no universal capacity is asserted from the selection guide.

Substitution guidance

Treat only the aliases on this page as exact equivalents. Another cell with the same dimensions is conditional at best unless its chemistry, nominal voltage and higher-drain requirement also agree with the device specification.

Fact-level evidence

Maxell Button and Coin Battery Cross-reference Table

Published by Maxell; SR621W row in the silver-oxide battery table. Checked 2 September 2026. Independently presented facts only; publisher wording, layout and diagrams are not reproduced.

Open primary source
Not a device-fit guarantee.

Confirm the exact code, chemistry and drain requirement with the device maker. Keep button and coin cells away from children and never recharge this primary cell.