Using a small, on-chip solar cell, NUS say that BATLESS is able to self-start and continue to function under dim light without any battery assistance. The team believe this will lead to cheaper batteries which are 10 times smaller than current batteries required to power IoT sensor nodes.
Battery indifference is the ability for IoT devices to continue operations, even when the battery is exhausted. It is achieved by operating in two different modes – minimum-energy and minimum-power. When the battery energy is available, the chip runs in minimum-energy mode to maximise the battery lifetime.
However, when the battery is exhausted, the chip switches to the minimum-power mode and operates with a tiny power consumption of about half a nanoWatt – this is about a billion times smaller than the power consumption of a smartphone during a phone call. Power can be provided by a very small on-chip solar cell that is about half a square millimetre in area, or other forms of energy available from the environment, such as vibration or heat.
The BATLESS microchip can uninterruptedly sense, process, capture and timestamp events of interest, and allows data to be wirelessly transmitted to the Cloud when the battery becomes available again.
Despite being in minimum-power mode when battery is not available, the team say the reduced speed of the microchip is still adequate for numerous IoT applications that need to sense parameters that vary slowly in time, including temperature, humidity, light, and pressure.
Associate professor Massimo Aliotoof NUS, says: “In minimum-power mode, BATLESS uses 1,000 to 100,000 times less power, compared to the best existing microcontrollers designed for fixed minimum-energy operation. At the same time, our 16-bit microcontroller can also operate 100,000 times faster than others that have been recently designed for fixed minimum-power operation.”
BATLESS is also designed to enable operations to be self-started while being powered directly by the tiny on-chip solar cell, with no battery assistance.
The NUS researchers are now exploring ways to build complete battery indifferent systems that cover the entire signal chain from sensor to wireless communications, expanding the current work on microcontrollers and power management.
The team aims to demonstrate a solution that shrinks battery to millimetres, with the long-term goal of completely eliminating the need for it at all.