Solar-powered electronics equipment/gadgets have been available for mobile as well as stationary applications. Yet, there are a multitude of unrealistic, advertised duration of usage for a specific load requirement that necessitated the inclusion of a back-up battery to sustain continuous load supply, specifically at diminished solar irradiance. The present study made use of experimental research design where relationships in rate of rise in charging voltage, energy discharge for lithium battery variants and 0.5V solar cells were observed at the highest and lowest solar irradiance with and without boost converter. Temperature, as determined to affect semiconductor performance, was maintained at 25 deg.C. The 0.5V cells were connected in series to achieve 4.5 V open-circuit voltage while connecting these modules up to 5 parallel configurations (termed as 1 module) to increase the current density. Using Kruskal Wallis test for significance and Dunn’s post-hoc test for pairwise comparison, the results revealed that at 19W/m2 (low solar irradiance), there is a significant difference in voltages, probably, due to the voltage drop inherent to the booster design with inductor. The energy density (Wh/kg) of lithium battery variants e.g. Lithium Manganate etc. were confirmed to agree on the findings stated in the literature and the power density (W/kg) of lithium iron phosphate appear to agree, as well. The microcontroller for LoRa used as test load required 3.3 volts consuming 70–110 mA. The 4.5-V module was able to supply 5.5mA at low solar irradiance (19W/m2) hence necessitating, at least, 16 shunt modules to operate without a battery. The test was made using 12 shunt modules and joystick coordinate was transmitted. However, with visible flicker which was partially eliminated thru a shunt filter capacitor. Data reception reached 34m with obstruction while increasing the solar irradiance to 30W/m2 consequently increased the communication distance to better than 164m. The results emphasize that stable power delivery rather than raw current magnitude, is the critical factor in enabling reliable solar-powered LoRa operation under low-irradiance conditions. Further test is recommended to determine the maximum transmission and reception distance using 16 modules or more to guarantee remote sensing data integrity and latency at the lowest solar irradiance of 19W/m2.

Keywords: Solar Cell Boost Converter, Solar-powered LoRa, Lithium Batteries for LoRa