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Same size, different electrical family

SR626SW / 377 vs LR626 / AG4

The 6.8 × 2.6 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.

Same size, different electrical family

The 6.8 × 2.6 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.

Top profile · Ø 6.8 mm
Side profile · 2.6 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
Top profile · Ø 6.8 mm
Side profile · 2.6 mm high
Original proportional profiles. Scale is consistent within this diagram; screen size is not a physical ruler.
FieldSR626SW / 377LR626 / AG4
Dimensions6.8 × 2.6 mm6.8 × 2.6 mm
Voltage1.55 V nominal1.5 V nominal
ChemistrySilver oxide / zincAlkaline manganese dioxide / zinc
DrainSW: low-drain profileGeneral-purpose alkaline; sloping discharge profile
RechargeableNo — primary cell; do not recharge.No — primary cell; do not recharge.

Direct answer

SR626SW/377 and LR626/AG4 both measure 6.8 × 2.6 mm. The watch cell is silver oxide at 1.55 V with an SW low-drain designation; LR626 is alkaline at 1.5 V with a general-purpose profile.

Both are 6.8 mm in diameter; heights are 2.6 mm and 2.6 mm. The 6.8 × 2.6 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.

Do not infer acceptability from fit alone. The device maker’s complete code and current instructions remain authoritative.

Why these codes are confused

SR626SW / 377 and LR626 / AG4 share part of their dimensions, naming pattern or retail context. The table separates the four fields that a one-line cross-reference can hide.

When the alternative may be acceptable

Only when the device or battery manufacturer explicitly permits the alternative after accounting for size, nominal voltage, chemistry and drain behaviour. Otherwise use the specified family. Never stack cells or modify a compartment to compensate for a height difference.