Embodiments include systems and methods for controlling power distribution and supply across independently powered modules in a storage library. Embodiments operate in context of a data storage library having a base module and one or more expansion modules. Each expansion module is independently powered, and each is in communication with the base module via a powered data communications network. In some embodiments, when the base module power supply is on, a base controller in the base module provides network power over the powered data communications network. The network power causes expansion controllers in each expansion module to boot up and power on the power supplies of their respective modules. When the base module is powered down, power is no longer available to the expansion controllers, and the respective power supplies can be hard-coded to shut down automatically under that condition.