3.6V LiSOCI2 ER26500 8.5Ah lithium battery pack for NB-IoT water meter gas meter non rechargeable C size primary lithium battery
The lithium thionyl chloride battery is connected in parallel with the HPC, and the lithium thionyl chloride battery charges the HPC with a small current through the voltage difference with the HPC. When powering externally, HPC bears most of the current output.