Arrohman, Donny Auliya, and Nafis Ainun Fikriyyah. 2018. “Implementation of Micro Usb Charger TP4056 and Battery Indicator LED in Portable Solar Charge”. Journal of Natural Sciences and Mathematics Research 4 (1):6-10. https://journal.walisongo.ac.id/index.php/JNSMR/article/view/10956.