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Does NFC drain battery?
Modern smartphones are constantly equipped with additional functions, but progress in battery research has been much slower. Therefore, smartphone users feel that they have to charge their battery increasingly often. Thus, it’s not surprising that many tips about saving battery power can be found on the Internet. Sometimes such tips also recommend to deactivate the NFC function. However, NFC doesn’t have to be deactivated because several intelligent mechanisms ensure that NFC doesn’t become an energy guzzler.
How is the power consumption reduced?
Descriptive explanation
The NFC chip inside the smartphone scans his environment regularly to detect NFC tags in reach. In order to scan the environment, the NFC chip has to be active, which is the reason for the assumed high power consumption of the NFC function. However, the NFC chip is actually in some kind of sleep mode and scans his environment only 10 times per second. This frequency is sufficient to identify possible NFC connection partners quickly, but saves a lot of battery power. Furthermore, scanning of the environment doesn’t require as much energy as establishing a connection to a NFC device. As data are transferred very quickly via NFC, a NFC chip only needs to provide enough energy to establish a connection for very short time frames. Even when connected with another device NFC is much more energy efficient than similar technologies such as Bluetooth or RFID.
Of course, Bluetooth and RFID chips also try to save battery consumption with similar mechanisms. However, there are some important differences between NFC and other technologies for data transmission. For example, Bluetooth and RFID have a significantly higher reach than NFC (several meters vs. 10 cm). Therefore, both technologies already consume more battery power while only scanning their environment.
Technical explanation
From the documentation of a typical NFC-IC (NXP MFRC522) can be learned that NFC chips consume approximately 40 mA while reading or writing NFC tags (active mode). However, NFC chips are only seldom in active mode as even chips with higher memory capacity such as the NTAG 216 are read and written in under one second. This means, that NFC chips actually spend a lot of time in sleep mode. While in sleep mode NFC chips scan their environment for possible communication partners. However, scanning the environment requires much less energy than establishing a NFC connection. During sleep mode NFC chips only consume between 3 and 5 mA. In case the energy-saving mode is activated energy consumption is even lower (5 micro-amp).
In comparison to Bluetooth, NFC is a more energy-saving standard for data transmission. While newer Bluetooth Low Energy chips consume approximately 15 mA, energy consumption of a typical Bluetooth chip is twice as high. This means, NFC chips (5mA) consume three times less energy than Bluetooth Low Energy chips (15 mA) and even six times less than Bluetooth chips (30 mA).
On top of that NFC functionalities are more and more often integrated into so-called combined chipsets. For example, the Toshiba TC35670 combines NFC and Bluetooth functionalities in a single chip. Thereby, the energy-saving potential of NFC is further enhanced, as only one combined chip has to be supplied with power. The popular smartphone chip manufacturer Broadcom also pushes the integration of NFC into the main chip forward.