The Low Power Wide Area Networks allow maintaining connectivity with devices over a distance of a few kilometres. However, due
to the presence of obstacles the communication range in an urban environment may be shorter, which creates multiple blind spots or
areas with limited coverage. The nodes acting as relays may solve this problem by forwarding the data from other devices with poor
connectivity. We propose and investigate a novel algorithm that assigns devices to the relay role while keeping the battery constraints.
We define the algorithm, describe the simulation testbed, and present performance evaluation in several scenarios, including real-life
topologies of IoT networks. The proposed relay selection scheme allows increasing the lifetime of the network by selecting the relay
taking into account the current battery capacity. Additionally, it outperforms a previously proposed relay selection algorithm for LP
WAN, showing an average 4% decrease in transmission time and an order of magnitude lower computation complexity.