Lithium-ion batteries power all sorts of technology, from handheld electronics to light rail cars, and will only grow more popular in the years to come. In fact, the worldwide use of lithium-ion cells is expected to double by 2016, according to Jim Greenberger, the executive director of the advanced battery trade group NAATBatt.
Over the past several years, a small number of battery failures have led to fires that are rare, but concerning. The U.S. Consumer Product Safety Commission has documented more than 350 fires involving lithium-ion batteries since March 2012.
As lithium-ion batteries show up in more and more household and industrial products, UL is working to update existing safety standards and create new ones that apply to a battery’s ability to withstand both normal and unexpected wear.
Today’s standards for lithium-ion and other rechargeable batteries include tests that put the battery under stress through short circuiting, abnormal charging, forced discharge, vibration, shock, crush, cell impact, temperature cycling, heating, altitude simulation and projectile/fire exposure. At the cell level, UL is working to develop and add a new internal short circuit test that would become part of the existing standard. In that test, researchers cause a battery to short circuit by slowly denting one of the cells. This indentation-induced short circuit allows them to see what stress a battery can take under different conditions without failing.
For larger-scale batteries, UL is updating the standards that cover electrical energy storage assemblies for on-road and off-road vehicles. Tests include short circuit, abnormal charging, forced discharge, vibration, shock, crush, cell impact, temperature cycling, heating, altitude simulation and projectile/fire exposure.
Making sure standards evolve to keep up with technology is important, not only as lithium-ion batteries appear in more and more everyday appliances and tools, but also as the batteries are expected to last longer. In consumer electronics, expected battery life is one to three years, but electric vehicle manufacturers expect the cells will last five to 15 years before they should be replaced.
To explore how aging may affect battery safety, UL has tested a commonly used lithium-ion battery at two temperatures (25°C and 45°C) over 50, 100, 200, 300, 350 and 400 charging cycles, adding in abuse tests to see how the battery performed. As new tests examine aging effects on larger batteries, such as the ones used in electric vehicles, standards will be updated in an effort to bring safety and performance together to power technology.