Li-ion Battery Two-region Polynomial Piecewise State-of-charge Model for a Portable Datalogger Applied to Technosol Studies

State-of-charge estimation of a battery powered datalogger is an important feature for determining the remaining operation time. A two-region piecewise model for determining the capacity of a 3.7 V Li-ion battery based on two low-order polynomials and suitable for low-power embedded systems is introduced. The model is applied to a datalogger used in technosols studies and based on an Arduino MKR ZERO board. Data from soil pH, temperature and volumetric water content is stored in a microSD card. Details of the design and tests are presented.