A power distribution unit for a vehicle including an enclosure and power distributing means for distributing electrical power between a battery and a load application, the enclosure including an external casing and an internal casing having a faceplate and a mounting plate, the mounting plate having upper dielectric partitions protruding upward from a top face of the mounting plate, and the power distributing means being mounted on the mounting plate, wherein the upper dielectric partitions are configured to both maintain a separation between different voltage groups and define an insulating barrier between components of the power distributing means, the internal cartridge is configured to be inserted into the external casing, and the enclosure is configured to be sealed from an external environment.