Lithium batteries are charged using a CCCV (or CC/CV) charging profile. The picture below illustrates a CCCV charging cycle for a single lithium-ion cell. The example is for a small cell (think smartphone), but the concept is the same for the large format cells we use in our EVs. In this case, the lithium-ion cell is spec'ed to charge at a constant current of 1A (1000ma) until the cell voltage reaches 4.2V and then the voltage is held constant as the current decays to 0A. i highlighted the various parts of the picture using these colors:
yellow = charging current (1A to 0A when completed)
blue = cell voltage (3.6V to 4.2V when completed)
green = cell capacity (SOC (State of Charge) from 0 to 100%)
red = shows when the charger changes from constant current to constant voltage
