Dead battery

Dead battery: what do I buy?

Three steps. Skip any you cannot do. The answer updates as you go.

1. 1 What does it look like?

   Flat coinWide, thin, often starts with CR or BR Small buttonWatch or toy cell, under 12 mm Hearing-aid cellButton with a sticker tab or air holes Small cylinderA23, A27, N, CR123A Box or pack9 V, CR-P2, 2CR5 Not sureSearch everything

2. 2 Measure it

   Calipers are best. A ruler gets the diameter close. Height is the thickness of a coin or the length of a cylinder.

   Diameter, mm Height, mm Tolerance±0.15 mm±0.3 mm±0.5 mm

   No ruler? Lay the cell on the screen at true size.

3. 3 Read the code printed on it

   Look at the flat face. Wipe it and tilt it under a light. The code is often tiny: CR2032, LR44, SR626SW, 377, 312.

   Code on the cell