This reference design showcases three different power architectures for smart flow meters with lithium manganese dioxide (LiMnO2) primary batteries and commercial off-the-shelf narrowband modules for Internet of Things (IoT)-related applications. The three power solutions are combined with the Battery and System Health Monitoring of Battery Powered Smart Flow Meters Reference Design hardware: which provides highly-accurate State-of-Health (SOH) calculation for the battery lifetime. The always-on in-system current monitoring detects the current peak of the RF transmission and the SOH measurement is scheduled afterwards with an adjustable delay. High-efficiency power architectures for supplying narrowband cellular modules for IoT-related applications with the BQ35100 battery gauge delivers real-time battery life data enabling on-demand battery replacement.