Abstract: Systems, devices, and methods for thermal malfunction detection in a liquid cooled vehicle battery are disclosed herein. Systems can include a housing enclosing at least a portion of one or more electrochemical cells, a flow path at least partially disposed within the housing and at least partially in thermal contact with at least a portion of the one or more electrochemical cells, and a thermal malfunction detector disposed at least partially within the flow path. The thermal malfunction detector can be capable of detecting matter output by the one or more electrochemical cells during a thermal malfunction. Matter output during a thermal malfunction may include smoke.