The battery life of a cordless sprayer depends on a number of factors, including the type of battery used, the size of the tank, the type of paint being sprayed, and the spraying pattern. Most cordless sprayers will come with a lithium-ion battery, which offers the longest battery life. The size of the tank will also affect the battery life, as a larger tank will require more power to operate. The type of paint being sprayed can also affect the battery life, as thicker paints will require more power to atomize. Finally, the spraying pattern can also affect the battery life, as a wider spray pattern will require more power to maintain.