  From the outset, batteries have been the main power source for the Internet
of Things (IoT). However, replacing and disposing of billions of dead batteries
per year is costly in terms of maintenance and ecologically irresponsible.
Since batteries are one of the greatest threats to a sustainable IoT,
battery-less devices are the solution to this problem. These devices run on
long-lived capacitors charged using various forms of energy harvesting, which
results in intermittent on-off device behaviour. In this work, we model this
intermittent battery-less behaviour for LoRaWAN devices. This model allows us
to characterize the performance with the aim to determine under which
conditions a LoRaWAN device can work without batteries, and how its parameters
should be configured. Results show that the reliability directly depends on
device configurations (i.e., capacitor size, turn-on voltage threshold),
application behaviour (i.e., transmission interval, packet size) and
environmental conditions (i.e., energy harvesting rate).
