1. What it is
A 3-volt lithium cell about 34.5 mm long and 17 mm wide. It holds far more energy than a coin cell and keeps working in cold weather.
2. Where you’ll find it
Digital cameras, LED torches, some door and window sensors and some smoke alarms. Many devices print CR123A inside the battery compartment.
3. It’s not a rechargeable cell
The 16340 is almost the same size, but it is a 3.7-volt rechargeable lithium-ion cell. It is not a replacement for a CR123A, so only use it where the device says it takes one.
4. Its near-twin: the CR2
The CR2 is also a 3-volt lithium cell, but it’s shorter and thinner, at about 15.6 mm wide and 27 mm long. It won’t fit a CR123A slot. Read the code, not just the voltage.
5. Store spares carefully
Keep them in their pack until you need them. Loose lithium cells can touch each other, so tape the ends of any spares kept in a drawer.