The SR1116 is a wide, very thin 1.55 volt silver-oxide cell: 11.6 mm across and only 1.65 mm tall. The high-drain version sells as the 365 (SR1116W) and the low-drain watch version as the 366 (SR1116SW). Capacity runs 30 to 45 mAh depending on maker.
SR1116W, face and side profile, drawn to scale: 11.6 mm across, 1.65 mm thick.
Voltage
1.55 V
Size (D×H)
11.6 × 1.65 mm
Chemistry
Silver oxide (Ag2O)
Capacity
30-45 mAh
Same battery, other names
Every code below is the exact same cell as SR1116W. Any of them will fit and work identically.
365SR1116SW (366, low drain)
Buying and replacement notes
This is the thinnest member of the 11.6 mm family that also holds the 391/381, 389/390, 386 and 357. Slim instruments and flat devices favor it for its footprint-to-height ratio. Match the drain type where you can: 366 for a quiet analog movement, 365 where the device pulses current. Neither the 391 nor any taller 11.6 mm cell can substitute.
⚠️ Keep away from children. Swallowed button batteries, especially 20 mm lithium coins, cause severe injury within hours. If a child swallows one, call the 24/7 National Battery Ingestion Hotline (US) at 800-498-8666 or poison control at 800-222-1222 immediately. What every parent should know.
Frequently asked questions
What is the difference between 365 and 366?
They are the same SR1116 case, 11.6 x 1.65 mm, with different electrolytes. The 365 (SR1116W) is the high-drain type for devices with current spikes; the 366 (SR1116SW) is the low-drain type for simple analog watches. Physically they interchange.
Is there an alkaline equivalent to the 365?
No commonly sold one. The 11.6 x 1.65 mm format exists almost exclusively in silver oxide. If a device specifies a 365 or 366, buy exactly that; the nearest alkaline cells in this diameter are the thicker LR1120 and LR1130, which will not fit.
How long does a 366 last in a watch?
Around two years in a slim analog movement, sometimes longer given the cell's respectable capacity for its thickness. Silver oxide holds a flat 1.55 V, so the watch keeps time accurately until the cell is effectively empty.