I purchased four AirTags about year and a half ago. I replaced the batteries in three of them after about 14 months. The fourth AirTag, however, has required a new battery every 3 or 4 months.
Does anyone know why this would happen? Should I just contact Apple Support?
AirTag
Under normal conditions, the AirTag's battery should last approximately one year. Every 3-4 months, as in this case, seems unusual ... unless the batteries are defective or you use this AirTag in an environment at either end of its normal operating temperature band.
It's also possible that this particular tag is defective. They normally only transmit their ID info via a Bluetooth beacon that transmits every 3-5 mins. It could be that it is transmitting constantly, similar to how a GPS tracker operates, which will run down a battery quickly.
AirTag Needs Frequent Battery Replacement
