BATTERY PACK

A battery pack includes a battery module () and lid modules. The battery module () comprises a liquid-limiting casing () having a peripheral wall () that includes a module-wall-vertical-channel (). A circuit board is disposed within the module-wall-vertical-channel (). A flexible circuit member is electrically connected to the circuit board and extends laterally into a battery-pack space () to connect to battery-cell-connecting members (). The flexible circuit member performs at least one of sensing a state of battery cells and heating the battery cells. This configuration maximizes internal volume utilization by integrating electronic components into the peripheral wall () of the liquid-limiting casing () and utilizes the flexible circuit member to reliably manage thermal and mechanical stress within the immersion environment.