What happens during a battery thermal event in an AES SAFE chamber?

Battery thermal events can develop rapidly and unpredictably, making automatic hazard mitigation an important part of battery test chamber safety. AES SAFE chambers are designed to automatically respond to an alarm condition without requiring an operator to immediately approach the chamber.

What happens when a thermal event is detected?

When a chamber alarm condition is triggered, the SAFE chamber automatically initiates an inert gas purge.

The purge is designed to reduce the oxygen concentration within the chamber and help mitigate and contain the event. The system continues purging while the triggering alarm condition remains active, with a minimum purge duration of 5 minutes at 5 CFM. This provides approximately three complete chamber-volume changes.

If the alarm condition returns after clearing, the purge cycle automatically restarts.

Is operator intervention required during the initial response?

No. The immediate inert gas purge is initiated automatically when the appropriate chamber alarm condition is triggered. An operator does not need to manually initiate the purge or immediately approach the chamber to activate the safety response.

This allows the chamber to begin its hazard-mitigation sequence while keeping personnel away from the chamber during the initial event.

Does the inert gas purge extinguish the fire?

The inert gas system should be understood as a hazard-mitigation and containment measure, not as a guaranteed fire-extinguishing system.

Reducing the available oxygen within the chamber can help mitigate and contain a thermal event. However, a battery cell experiencing thermal runaway can continue to generate heat and gases, and the inert gas purge should not be characterized as a guaranteed method of extinguishing a cell in thermal runaway.

The specific response to a thermal event can depend on the test article, chamber configuration, and nature of the event.

What happens after the event?

Operator involvement is required after the  event to evaluate the chamber and Device under Test (DUT) and determine when it is safe to access the chamber.

Following an event, a manual CDA (clean, dry air) flush is used to evacuate the chamber before the chamber is opened or serviced.

Personnel should follow the appropriate post-event procedures and should not open the chamber until it has been determined to be safe to do so.

Key Takeaway

AES SAFE chambers are designed so that the initial hazard-mitigation response is automatic. An operator does not need to approach the chamber to manually initiate the inert gas purge when an appropriate alarm condition occurs.

The inert gas system is intended to reduce oxygen concentration and help mitigate and contain a thermal event, rather than serve as a guaranteed fire-extinguishing system. Human involvement is still required after the event for evaluation, post-event procedures, and determining when the chamber can be safely accessed.