Watch battery · silver oxide
SR521SW (379) battery
SR521SW = 379 = SB-AC. 5.81 × 2.15 mm1 Sources disagree: manufacturer 2.15 mm / secondary source 2.1 mm2 silver oxide, 1.55 V1. Equivalents: V379, B-379L, 618, 280-59, 9938, 080-D39 and 5 more (14 codes in 12 code systems, full table); 38 calibres, modules and models in our base take it.
Size and chemistry
Show SR521SW at true size (1:1)
Cell types in this size
SR521SW
Low drain (SW): for plain analog watches · Silver Oxide3
13 codes in our sources name this cell type.
LR521
Alkaline cell of the same size: the IEC digits are the size, the L is the chemistry. LR521 lands on this page by that rule; our sources hold no alkaline datasheet for it, so no figures are shown.
Capacity by manufacturer
Energizer 379SR521SW
14.5 mAh3cutoff 1.2 V as printedDatasheet ↗
Can I use another cell instead of 379?
Verdicts follow our swap rules from the datasheet size, voltage and cell type.
Use instead of SR521SW
LR521
Fits, with a catchFits, but LR521 is alkaline and runs shorter.
Same 5.8 mm × 2.15 mm size. LR521 is an alkaline (L) cell; the watch is made for silver oxide (S). Use it to get the watch going, then fit SR521SW.
Draw both cells in the swap checkerNo: SR516SW is 0.5 mm thinner than SR521SW.
Same 5.8 mm diameter, but SR516SW is 1.65 mm against 2.15 mm: the contact spring may not reach it.
SR516SW: 5.8 mm4 × 1.65 mm4, 1.55 V4
Draw both cells in the swap checkerNo: SR527SW is 0.55 mm taller than SR521SW.
Same 5.8 mm diameter, but SR527SW stands 2.7 mm against 2.15 mm: the case back presses on it or does not close.
SR527SW: 5.8 mm4 × 2.7 mm4, 1.55 V4
Draw both cells in the swap checker
What uses 379
38 calibres, modules and models in our base name this size.
Seiko calibres37[5]
Seiko's battery chart gives 2–3 years of battery life for these calibres. Seiko, Pulsar, Lorus and Alba calibres share the chart.
- 1N01A
- 1N01B
- 2B20
- 2B21
- 2B31
- 2C20
- 2C21
- 2E20A
All 37 calibres
- 2E50
- 2E70
- 2E20B
- 2G38
- 2G98
- 2P21
- 2Y01
- 2Y07
- 4J27A
- 4J27B
- 4J51A
- 4J51B
- 4N01
- 7G21
- V220
- V220B
- V230
- V231
- V232
- V233
- V235
- V401
- VC00
- VC01
- VC11
- WWW1
- V232
- WWW2
- V220B
Citizen models2[6]
On 1 calibre, from Citizen's battery table.
- 59302 models
The 2 model numbers
EJ5850-57E · EJ5854-56A
Warnings from the makers
Not a stand-in for a 3 V lithium cell
“are 3 volts, not 1.5 volts and cannot be substituted for a 1.5 volt silver oxide watch battery”[2]secondary source
Questions
What is the 379 battery equivalent?
SR521SW, V379, B-379L, 618, 280-59, 9938, 080-D39, SB-AC, SR521, SR63 and 2 more codes name the same 5.8 × 2.15 mm silver oxide cell as 379. Any maker's cell under one of these codes fits.
Is 317 the same as 379?
No. SR516SW is 0.5 mm thinner than SR521SW. Same 5.8 mm diameter, but SR516SW is 1.65 mm against 2.15 mm: the contact spring may not reach it.
Is LR521 the same as SR521SW?
No: LR521 is an alkaline cell of the same size, SR521SW is silver oxide. Fits, but LR521 is alkaline and runs shorter. Same 5.8 mm × 2.15 mm size. LR521 is an alkaline (L) cell; the watch is made for silver oxide (S). Use it to get the watch going, then fit SR521SW.
What watches use the 379 battery?
In our base: 37 Seiko calibres (1N01A, 1N01B, 2B20, 2B21…); 2 Citizen models. The full lists are on this page, with the brand tables they come from.
How long does a 379 battery last in a watch?
Seiko's battery chart gives 2 to 3 years for its 37 calibres on this cell, 2 years most often. Life depends on the calibre's current draw, not on the cell alone.
Seiko battery chart[5]
Sources
Documents checked · Report a wrong number
- 1Murata Manufacturing Co., Ltd. — Watch Battery Selection Guide / Cross Reference (1 page) · pdf · read
- 2WatchBattery (UK) Ltd — Watch Battery Cross Reference Table · html · read
- 3Energizer Holdings, Inc. — Product datasheet ENERGIZER 379 · pdf · read
- 4Murata — Watch Battery Selection Guide / Cross Reference · pdf · read
- 5Seiko Watch Corporation (service information) — Value Checking List / Battery No. Cross-reference Chart · pdf · read
- 6Citizen Watch US — Battery Information (model / caliber / battery table) · html · read