Why does it take longer to charge a mobile phone toward the end?
From experience, we understand the speed at which a smartphone charges its battery slows down toward the end. Where it takes a certain amount of time to charge 80-85%, this final portion, which is 15-20%, takes a good length of time. Why? The reason has something to do with the nature of lithium batteries used in smartphones. Generally, these batteries follow some preordained process for charging when plugged into a power source. As the battery charge is low at the initial stage, the empty cells inside the lithium-ion battery can afford to adjust to the ions quite easily. Fast charging means a high flow of electricity under increased pressure. Once the charge has gone up to 80-85%, the remaining ions take more time to find free cells in the layers of the battery. At this stage, some special batteries temporarily stop charging for 5 to 10 minutes or reduce the rate at which charges get in to make the ions settle. That's analogous to traffic control at a busy junction where, to preve...