A system for detecting thermal events, e.g., thermal runaway, within a sealed battery pack based on a characterization of monitored pressure variations within the pack is provided. The system includes at least one pressure sensor coupled to the battery pack and to a pressure monitoring system that outputs pressure data representative of the battery pack pressure over time; a system controller that analyzes the pressure data and outputs a control signal when the pressure data fits a specific curve shape; and a thermal event response subsystem that performs a preset response upon receipt of the control signal from the system controller. The system may include a secondary effect monitoring system, wherein the thermal event response subsystem performs the preset response when the pressure data fits a specific curve shape and the secondary effect is detected by the secondary effect monitoring system.