Power supply system

A power supply system includes a power conversion device, a battery unit that is electrically connected to the power conversion device via a wiring, and a case. The case includes a first case portion that defines a first internal space for housing the power conversion device, a second case portion that defines a second internal space for housing the battery unit, and a partition wall portion that separates the first internal space and the second internal space from each other and has a connecting hole that connects the first internal space and the second internal space to each other. The first case portion has an opening portion that opens downward. The connecting hole is positioned above the opening portion. The power supply system further comprising a lid member that is capable of opening and closing the opening portion.