By Emanuele Signoretta on May 20, 2021
This uses a buck converter as a 5V Output to charge the battery(Li Po/Li-ion). And Boost converter for 3.7V battery to 5V USB output for devices needed 5 V. Similar to the Original system that uses Lead Acid Battery as an energy storage charge by either PWM or MPPT controller. And supply for 12V Devices. This One only uses a Buck converter to convert 12V (solar panel nominal voltage) to stable 5V to charge a Li-Po/Li-ion battery, after daylight. Switch to Boost converter to convert the battery’s voltage 4.2 (3.7 nominal voltage for Li-Po and Li-ion) to again 5V for devices powers 5V. (You can still use the 5V in the Buck Converter during daytime while the Li-Po/Li-ion Battery is charging. It might not be as efficient as the original system(12V). I only did this because my solar panel power is only 15W and not enough budget to buy MPPT or PWM charger for 12V. and not enough to power applications that need higher than 50W. So I make an alternative option, the 5V version.