Electric power storage system

An electric power storage system for a vehicle, the electric power storage system comprising:

• an electric power storage device configured to supply electric power to a traveling motor of the vehicle;
• a converter configured to perform voltage conversion between the electric power storage device and the traveling motor;
• a DC/DC converter disposed on a current path between the electric power storage device and the converter and configured to step down an output voltage from the current path to an auxiliary machine or an auxiliary machine battery mounted in the vehicle;
• a charger configured to charge the electric power storage device with external electric power supplied from an external electric power source;
• a first relay disposed on a first connection line as one of positive and negative electrodes connecting the electric power storage device to the converter;
• and
• a second relay disposed on a second connection line as the other one of the positive and negative electrodes connecting the electric power storage device to the converter,
• wherein one end of the DC/DC converter is connected to the first connection line between the first relay and the converter and the other end of the DC/DC converter is connected to the second connection line between the electric power storage device and the second relay, and
• wherein the charger is disposed on a current path capable of charging the electric power storage device with the external electric power when the first relay is in an ON state and the second relay is in an OFF state.