The Bomb in Your Pocket?

Paul Orange explains why testing battery safety matters more than you’d imagine

ON 7 JANUARY 2013, a Japanese airlines plane at Boston Logan International Airport was evacuated when a worker noticed smoke. The emergency services found a fire in the belly of the aircraft which was caused by the plane’s lithium ion batteries catching fire. This led to the Federal Aviation Administration (FAA) mandating the grounding of all Boeing 787 Dreamliner planes and forced a redesign of the battery system. Three years later, Samsung suspended sales of its new flagship Galaxy Note 7 smartphone after 35 devices caught fire or exploded while charging. The cost of these two events is predicted to have been US$17.6bn^1,2.

Both instances highlight the critical importance of battery safety testing and adherence to various testing standards around the world. Since these events, battery testing standards have become stricter – most notably, the Chinese regulations (GB/T 36276-2018) that came into force in 2019.

These regulations not only outline the requirements for battery manufacturers and integrators, but also for companies that manufacture battery test equipment.

Over the past few decades, battery research has seen a meteoric rise in interest as an unsurprising consequence of batteries becoming ever-present in powering and controling modern life. With this, corporate funding in battery storage has seen a big increase, with a recent report citing a 136% uplift between 2019–2020³. The focus on developing more effective batteries has never been higher – specifically, battery cells with shorter charging times, a longer overall useable life, or higher energy density. However, as well as enhancing performance, batteries need to operate safely in their intended application to avoid unnecessary costs, and – more importantly – injury and the loss of lives. Typically, with higher energy density comes a greater effect if the cell fails.

If a battery fails, the root cause can be any of a number of factors, ultimately leading to battery over-heating. Figure 2 illustrates the initial causes of a battery fire or explosion. Stresses from both normal and abnormal use will cause the cell to generate unwanted heat. If thermal management strategies and devices are implemented, this heat may be safely dissipated; however, when damage is so significant, or the thermal management system is insufficient, thermal runaway is a common outcome leading to fire or explosion. There are many options when it comes to providing adequate thermal management for battery packs, ranging from simply providing air vents in casework, spacing, or arranging cells in a pack in a new configuration, through to active cooling from air ventilation of liquid cooling loops.

For researchers in laboratories investigating novel batteries, these considerations can feel very distant; however, many tools exist that allow battery developers to evaluate the thermal safety and stability of a new device at the research stage.