A connection unit includes: a first terminal; a second terminal; a third terminal; a first switch part and a second switch part connected in series between the first terminal and the second terminal; a first diode; and a second diode, wherein the third terminal is connected between the first switch part and the second switch part that are connected in series, the flow of electricity in one direction between the third terminal and at least one of the first terminal and the second terminal is enabled and the flow of electricity in the direction opposite to the one direction is interrupted, by at least one of the first switch part and the second switch part is turned off, and flow of electricity between the first terminal and the second terminal is interrupted in both directions by the first switch part and the second switch part being turned off.