Lithium Ion batteries are generally charged using a two step process of constant current then constant voltage. https://www.digikey.com/en/articles/techzone/201

Lithium Ion batteries are generally charged using a two step process of constant current then constant voltage. https://www.digikey.com/en/articles/techzone/2012/nov/constant-voltageconstant-current-devices-optimize-li-ion-battery-charging-for-energy-harvesting https://www.digikey.com/en/articles/techzone/2012/nov/consta... If 80% is the set point to switch over from constant-current to constant-voltage, then yes, the charge rate will drop continuously until it reaches full charge.