381 battery equivalents
The 381 is a 11.6 × 2.05 mm silver-oxide cell, used in larger quartz watches, including chronographs. It's sold under several names: SR1120SW, SR1120W, 391, LR1120, AG8, 191, LR55, SR55.
Equivalents
| Sold as | Type | In a watch |
|---|---|---|
| SR1120SW, 381 | Silver oxide, low drain | Best for an ordinary analog quartz watch |
| SR1120W, 391 | Silver oxide, high drain | Works in any watch, and suits one with a backlight, alarm or chronograph |
| LR1120, AG8, 191, LR55 | Alkaline, 1.5 V | Fits, but runs down sooner and the voltage sags; use only in a pinch |
| SR55 | Older or alternative codes | Same size; check the chemistry on the pack |
Look-alikes that won't fit
These are also 11.6 mm across, so they look right in the pack, but the thickness is different. They aren't substitutes.
- 366 SR1116SW1.65 mm thick (-0.4 mm)
- LR1130 SR1130SW3.05 mm thick (+1 mm)
- 344 SR1136SW3.6 mm thick (+1.55 mm)
- 386 SR43SW4.2 mm thick (+2.15 mm)
- LR44 SR44SW5.4 mm thick (+3.35 mm)
Never use a lithium coin cell in its place. Lithium cells run at 3 volts, twice what a silver-oxide watch movement expects.
Getting a 381 changed
Watch shops in our directory list battery changes from $4.99 to $115, with a median of $15, usually done while you wait. A shop has the tools to open a screw-down caseback without marking it, and can replace the gasket and pressure-test a water-resistant watch. 455 shops in the directory list battery replacement. To do it yourself, follow how to change a watch battery.
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Questions
- Is 381 the same as 391?
- They're the same size (11.6 × 2.05 mm) and the same silver-oxide chemistry. The 381 (SR1120SW) is the low-drain version for ordinary analog watches; the 391 (SR1120W) is high-drain, for watches with a light, alarm or chronograph. The 391 works in any watch that takes a 381.
- Is LR1120 the same as SR1120SW?
- Same size, different chemistry. LR1120 (also sold as AG8) is alkaline and SR1120SW is silver oxide. The alkaline cell fits, but it holds about 30–45 mAh against 40–55 mAh and its voltage drops as it drains, so a watch runs a shorter time on it.
- Can I use a 366 instead of a 381?
- No. Both are 11.6 mm across, but the 366 is 1.65 mm thick and the 381 is 2.05 mm. A thinner cell won't press against the contacts, so the watch won't run reliably.
- How long does a 381 battery last?
- In a typical analog quartz watch, two to five years. It holds about 40–55 mAh; a running chronograph, a backlight or an alarm drains it faster. Unused cells keep for several years in the pack.