Search

Among the enhancements reflected in the Next Generation Li-ion Calorimeter is a rigidly wired system that allows direct mounting of thermocouples into key component locations to better capture thermal signature data during testing and improve thermocouple reliability. The ejecta mating chambers have also been modified for better thermal containment and easier system disassembly. Additionally, the system facilitates an easier access, user-friendly Destructive Physical Analysis (DPA) process between uses, and reflects durability improvements in the face of repetitive heat cycling. A clean-sheet redesign was undertaken to create a configurable insula-tion case with an interchangeable “window” section, tailored to the ex-perimental environment. For NASA’s Energy Systems Test Area (ESTA) evaluation, a window with the original foam is installed to maintain ther-mal insulation performance. In contrast, for synchrotron experiments, this section is replaced with an aluminum window that eliminates foam-related X-ray scattering. This modification has substantially improved X-ray radiography resolution, enabling clearer imaging of fine internal battery features during thermal runaway events. Moreover, the insulation case was designed to provide system fire-proofing for both the chamber and pouch cell testing case configurations. Lastly, a control switchbox is also being developed to work with the latest generation calorimeter. It allows users to remotely operate the TR trigger mechanism from a control room, automatically terminate power in a prescribed amount of time to prevent a fire caused by overheating, and provides lit indicators to inform the user of ready or fault states.

For years, NASA and the battery industry have been improving passive propagation resistant (PPR) Li-ion battery cell technology by enhancing their material and design choices. These efforts help ensure that a single cell’s TR event does not overheat adjacent cells or the entire battery pack ultimately causing fire or explosion. To improve cell integrity, single cells within battery packs are triggered into TR so that the battery pack can be analyzed for its TR resistance. ThermoArc operates by initiating a plasma arc, capable of delivering thermal energy up to 100W, to a very small (1mm diameter) section of the cell. The extremely localized high heat flux rapidly degrades a small section of the internal cell separator, resulting in a short circuit that leads to TR. This technology comprises several components: a high-turn-ratio step-up transformer capable of producing a minimum of 1,000 V upon the secondary winding, an H-bridge electronic circuit to drive the transformer on the primary side, two tungsten electrodes to deliver the plasma arc, and a power supply unit. ThermoArc applications may exist in any Li-ion battery cell/pack testing application where TR must be induced in an individual cell. Such applications could include testing of PPR battery packs to ensure single cell runaway does not cause catastrophic damage, more general battery destructive testing designed to better understand battery failure states, or other experimental testing. Companies interested in licensing this innovation may include those that manufacture internal short-circuit (ISC) cells or other devices used to induce TR at the individual cell level, battery testing firms, and Li-ion battery manufacturers with a focus on Li-ion battery packs for critical applications. ThermoArc is at a technology readiness level (TRL) 5 (component and/or breadboard validation in laboratory environment) and is now available for patent licensing. Please note that NASA does not manufacture products itself for commercial sale.