What is CC/CV mode?

Constant current / constant voltage (CC/CV) charging mode is a effective way to charge lithium batteries. When a lithium battery is nearly empty, we take constant current to charge it. We need to make sure that charging current should be lower than the max charging current that battery can accepted. With constant charing the voltage of battery is slowly upping, when battery volt reaches the max charging voltage, charger would make sure charging voltage fixed as "constant voltage" and reduce the charging current. When battery is fully charged this state would be stopped.