Both the CR123 and CR123a names refer to the same type of battery. Historically, the CR123 was a battery used specifically in cameras. In fact, many people still refer to these batteries as simply "camera batteries". But various electronics manufacturers recognized this battery, and they began using it as an alternative to AA batteries. As far as size goes, the CR123 is shorter and slightly fatter than the AA size. However, it still retains the cylinder shape.
For best results, we generally recommend using lithium CR123 batteries when possible. Lithium batteries will provide a longer power life than alternative battery types, such as alkaline batteries. Most lithium CR123 batteries will provide a lifespan of about five to six years, despite their small size. When the wireless sensor does have a low battery, the panel will display a message to let the user know that it needs to be replaced.
There are many wireless sensors that use the CR123 size. Honeywell is particularly fond of the size, and they have used it in many of their peripheral devices. Many of their life-safety sensors, including smoke detectors, heat sensors and carbon monoxide detectors, use CR123 batteries. The battery size is used often with Honeywell 5800 Series Sensors. Many 5800 Series motion sensors and door and window contacts use this battery. In fact, the CR123 is even used in Honeywell's most popular sensor of all-time, the Honeywell 5816. As a result, Honeywell users may want to stock up on CR123 batteries.
Replacing a CR123 battery is simple. These batteries can be popped in and out of a device with ease. When installing this battery type, always make sure that the positive and negative ends are facing the correct directions. A wireless sensor should power on as soon as a fresh battery is inserted.