Combining high-efficiency at light load, power converters with a primary battery gauge and a system health monitoring device deliver a unique capability: accurate measurement of the state-of-health (SOH) for LiMnO2 primary cells in NB-IoT enabled applications and report that information tirelessly over the cellular network. The system health monitor detects the high-current transmit pulse and triggers the time delay before the SOH measurement is made. The SOH measurement takes only 1 second and runs very infrequently, for example once in several days or weeks; the vast majority of the time the BQ35100 battery gauge is in shutdown mode consuming 50 nA (typical).

This in-system, real-time SOH ultra-low power measurement capability for IoT-related applications enables on-demand battery replacement and thus reduces the overall system cost. Instead of over dimensioning the cell capacity or simply replacing all cells after a predefined unit lifetime, designers now can get accurate SOH information per single unit and schedule the battery service only when this is necessary. As NB-IoT wireless network power settings are out of control for the IoT enabled devices and, in addition, the ever changing wireless environment is unpredictable, different units will experience a different discharge rate. The most accurate and cost-efficient solution is to measure in-system the battery discharge of each field-deployed unit and take action whenever the battery reaches a critical capacity level.