GM also plans to use a different battery supplier for the Spark than it uses for the Volt. For the Volt, it uses batteries made by LG Chem, a Korean company, although it had considered using batteries from A123 Systems—a comparatively new battery company at the time—which uses a novel, nanostructured electrode material for its batteries. Both LG Chem and A123 Systems produced full-sized Volt battery systems for testing.
“At that point, LG had a more mature manufacturing base for the Volt,” says Ronn Jamieson, GM’s director of global battery systems engineering. “A123 has significantly progressed in manufacturing since then,” he says. With the help of federal and state funds, A123 has built battery factories in Michigan, it can now make 30,000 electric vehicle batteries per year, and it has supply contracts with several automakers, including BMW, Fisker Automotive, and the large-vehicle manufacturer Navistar.
Jamieson says the A123 batteries were a good fit for the Spark EV in part because of their good energy storage, a key in a battery-only vehicle. A123’s lithium-ion electrode materials—made of lithium iron phosphate—actually store less energy than some types of lithium-ion battery by weight. But more of that energy can be used because the chemistry is more stable, Jamieson says. For some battery materials, only 50 to 80 percent of the energy can be used—discharging the battery more can damage the electrode materials and shorten the life of the battery. A123’s batteries can be discharged 90 percent or more.
In part because the Volt has been engineered to accommodate the specific characteristics of the LG Chem batteries, Jamieson says, GM will continue to use LG Chem batteries for the Volt.