A typical NFC transceiver draws ~50mA of current when powered up. For reference, this equates to around 25% of the total consumption of a typical smartphone with the screen powered on.
Left unchecked, this could have noticeable, adverse effect on battery life.
However, there are optimization techniques that can significantly reduce the effects of NFC on battery life. For instance, the Android NFC subsystem carries out the following:
- Intelligent polling - Android doesn't leave the NFC transceiver running at all times, instead it polls for tags at a rate around ~10Hz to conserve battery life. Maybe a feature in future ROMs would be the ability to change the polling frequency down to 1Hz.
- Polling disabled on screen lock - when the screen is locked Android ceases to poll for tags, however card emulation continues (this is how
- Google Wallet functions even when the screen is locked) .
- Screen off = NFC off - the NFC radio is powered down when the screen is locked.
