A shovel, comprising: a lower-part movable body; an upper-part turnable body turnably mounted on the lower-part movable body; a boom including a first end rotatably attached onto the upper-part turnable body; an arm including a first end rotatably attached to a second end of the boom; a work element rotatably attached to a second end of the arm; an electrical energy storage device including a plurality of electrical energy storage cells (19-1 to 19-n), and mounted on the upper-part turnable body and an electrical energy storage managing unit; an electrical energy storage unit, the electrical energy storage unit including the electrical energy storage device; and wherein the electrical energy storage managing unit further includes equalizer circuit parts (141-1 to 141-n) and an equalization control part configured to obtain the information on the cell voltages from the plurality of voltage measurement parts (149-1 to 149-n) and output the obtained information to the controller, a controller configured to control a charge and a discharge of the electrical energy storage device; and a plurality of voltage measurement parts (149-1 to 149-n) configured to measure respective cell voltages of the plurality of electrical energy storage cells (19-1 to 19-n), wherein information on the cell voltages is transmitted to the controller; wherein the controller comprises an equalization necessity determining part; characterized in that the equalization necessity determining part is configured to determining the presence or absence of a system abnormality; wherein the equalization necessity determining part is configured to determine the presence or absence of an abnormality in communications between the controller and the electrical energy storage managing unit, an abnormality in communications between the equalization control part and each of the equalizer circuit parts (141-1 to 141-n), and an abnormality in voltage measurement in each of the voltage measurement parts (149-1 to 149-n). a lower-part movable body; an upper-part turnable body turnably mounted on the lower-part movable body; a boom including a first end rotatably attached onto the upper-part turnable body; an arm including a first end rotatably attached to a second end of the boom; a work element rotatably attached to a second end of the arm; an electrical energy storage device including a plurality of electrical energy storage cells (19-1 to 19-n), and mounted on the upper-part turnable body and an electrical energy storage managing unit; an electrical energy storage unit, the electrical energy storage unit including the electrical energy storage device; and wherein the electrical energy storage managing unit further includes equalizer circuit parts (141-1 to 141-n) and an equalization control part configured to obtain the information on the cell voltages from the plurality of voltage measurement parts (149-1 to 149-n) and output the obtained information to the controller, a controller configured to control a charge and a discharge of the electrical energy storage device; and a plurality of voltage measurement parts (149-1 to 149-n) configured to measure respective cell voltages of the plurality of electrical energy storage cells (19-1 to 19-n), wherein information on the cell voltages is transmitted to the controller; wherein the controller comprises an equalization necessity determining part; characterized in that the equalization necessity determining part is configured to determining the presence or absence of a system abnormality; wherein the equalization necessity determining part is configured to determine the presence or absence of an abnormality in communications between the controller and the electrical energy storage managing unit, an abnormality in communications between the equalization control part and each of the equalizer circuit parts (141-1 to 141-n), and an abnormality in voltage measurement in each of the voltage measurement parts (149-1 to 149-n).