The patent encumbrance of large automotive NiMH batteries refers to allegations that corporate interests have used the patent system to prevent the commercialization of nickel metal hydride (NiMH) battery technology. Nickel metal hydride battery technology was considered important to the development of battery electric vehicles (BEVs or EVs), plug-in hybrid electric vehicles (PHEVs) and hybrid electric vehicles (HEVs) before the technology for lithium-ion battery packs became a viable replacement.
Background
The modern nickel-metal hydride (NiMH) electric vehicle battery was invented by Dr. Masahiko Oshitani, of the GS Yuasa Corporation, and Stanford Ovshinsky, the founder of the Ovonics Battery Company, and granted a patent. The current trend in the industry is towards the development of lithium-ion (Li-Ion) technology to replace NiMH in electric vehicles. In 2009, Toyota tested lithium batteries as a potential replacement for the nickel metal hydride batteries used in its Prius model gasoline-electric hybrid. The company said that it would continue to use NiMH batteries in the Prius, but would introduce an all-electric vehicle based on lithium technology. Li-Ion technology, while functionally superior due to its higher specific energy and specific power, is more expensive and, as of 2009, relatively untested with regards to its long-term reliability. In 2007, the National Renewable Energy Laboratory said that Li-Ion batteries may be subject to dangerous overheating and fire if cells are controlled incorrectly or damaged. In 2011, the National Highway Traffic Safety Administration investigated the safety of lithium battery powered vehicles and concluded that they pose no more risk of fire than other vehicles.
According to the United States Department of Energy the primary advantages of lithium batteries include their high power-to-weight ratio, high energy efficiency, good high temperature performance, and low tendency to spontaneously discharge when left unused for extended periods of time. Nickel metal hydride batteries have higher self-discharge, tend to generate heat at high temperatures, and have problems with hydrogen loss. However, none of these problems prevented the use of nickel metal hydride batteries in the Toyota Prius, which has an excellent reliability rating.
Market feasibility in the 1990s
The 1999 GM EV1 production vehicle, powered by nickel metal hydride batteries, had a 26.4 kWh battery and an EPA range of 105 miles.
The 2011 Nissan Leaf production vehicle had a 24 kWh battery and an EPA range of 84 miles.
Despite having not only a shorter range, but also a battery of smaller capacity than the 1999 GM EV1, the Leaf found 200,000 buyers worldwide before battery capacity was first increased in 2016.
Based on this, the claim that the NiMH technology was not sufficiently advanced in the 1990s seems false (at least with regard to two-seater cars that could more easily accommodate a battery of relatively large dimensions and weight).
General Motors and the US Auto Battery Consortium
In an interview in the 2006 documentary Who Killed the Electric Car?, Ovshinsky stated that in the early 1990s, the auto industry created the US Auto Battery Consortium (USABC) to stifle the development of electric vehicle technology by preventing the dissemination of knowledge about Ovshinky's battery-related patents to the public through the California Air Resources Board (CARB).
According to Ovshinsky, the auto industry falsely suggested that NiMH technology was not yet ready for widespread use in road cars. Members of the USABC, including General Motors, Ford, and Chrysler, threatened to take legal action against Ovshinsky if he continued to promote NiMH's potential for use in BEVs, and if he continued to lend test batteries to Solectria, a start-up electric vehicle maker that was not part of the USABC. The Big Three car companies argued that his behavior violated their exclusive rights to the battery technology, because they had matched a federal government grant given to Ovonics to develop NiMH technology. Critics argue that the Big Three were more interested in convincing CARB members that electric vehicles were not technologically and commercially viable.