Systems and methods for storing energy for use by an electric vehicle are disclosed. Systems can include an electric vehicle battery pack including a rack configured to couple a plurality of independently removable battery strings to the vehicle, the battery strings configured to be selectively coupled in parallel to a vehicle power bus. The battery strings may include a housing, a plurality of electrochemical cells disposed within the housing, a circuit for electrically connecting the electrochemical cells, a positive high-voltage connector, a negative high-voltage connector, a switch within the housing, and a string control unit configured to control the switch. Each battery string can include a coolant inlet and a coolant outlet configured to couple with and sealingly uncouple from an external coolant supply conduit and an external coolant return conduit, and an auxiliary connector configured to couple with an external communications system and/or an external low-voltage power supply.