As it is clear from the name“Constant Voltage”or CV is when a constant voltage is applied to the battery pack.This voltage is a preset value given by the manufacturer.This method is accompanied with a current limiting circuit most of the time，especially for the beginning periods of charging where the battery easily takes high rates of current comparing to its capacity.The current limitation value mainly depends on the capacity of the battery.This method is usually used for leadacid batteries，also for Li-ion batteries while using current limiter to avoid overheating the battery especially in the first stages of the charging process.