RADIO FREQUENCY TRANSACTION WITH A MOBILE DEVICE HAVING A DEPLETED BATTERY

For a mobile device having a main battery and a backup power source, a method is provided for wirelessly charging the backup power source using a reader when the main battery of the mobile device is fully depleted and unable to provide enough power for an RF transaction. The reader detects the mobile device cannot perform the RF transaction. In response, the reader generates an RF field that provides charge for the backup power source of the mobile device. After charging is complete, the mobile device performs the RF transaction using the charged backup power source. In one embodiment the mobile device is a mobile phone being used as a digital key and the reader is implemented in a smart door handle of an automobile that is unlocked by the RF transaction.