History of Vehicle Electrification 17 quickly followed by the modern nickel-metal hydride (NiMh), which was introduced in the mid-1990s. With the rapid spread of personal electronics, these high energy-density batteries became the energy storage solution of choice for many different applications from portable electronics to hybrid and electric vehicles. One of the biggest drivers in the United States for this new effort to electrify vehicles occurred in 2000 when California passed a Zero Emissions Vehicle (ZEV) mandate.
This was one of the first pieces of legislation in the United States that required manufacturers to offer vehicles that emitted no emissions whatsoever; essentially this legislation man- dated the introduction of electric and fuel cell vehicles. This was actually an evolution of an earlier ZEV legislation passed in 1990 as part of California’s Low Emission Vehicle (LEV) program that was intended to begin stemming the growing amount of air pollution in California. Perhaps, the first truly production-intent electric vehicle was General Motors’ (GM) EV1. It was intended to be an optimized vehicle platform designed from the ground up entirely for electrification.
The earliest versions of this vehicle used lead–acid (PbA) batteries, but later vehicles switched to nickel-metal hydride (NiMH) by Ovonic Battery Company, which reduced the size of the battery by about 50% while offering about the same amount of energy storage capacity. And while only 1117 vehicles were produced during its production run between 1996 and 1999, this vehicle became the basis for many of the electric vehicles that followed and formed a cult following among enthusiasts and early adopters. General Motors followed the EV1 with the development of a “Parallel Hybrid Truck” (PHT), and then joined in a partnership with Chrysler, Daimler, and BMW to develop a 2-Mode Hybrid System.
The 2-Mode was a strong hybrid that integrated a 300-V NiMH battery under the rear seat. At the same time as the 2-Mode was in development, GM also developed a “Belt-Alternator-Starter” (BAS)-type mild hybrid system. The first introduc- tion of GM’s BAS was a 36-V system with a NiMH battery developed by Cobasys (Cobasys, 2006); however, the second generation (now referred to as e-Assist) increased the voltage of the system to 115 V and changed to a 0.5 kWh lithium-ion air-cooled battery designed by Hitachi Vehicle Energy Ltd (Dlegs Hybrid Cars, 2011). All of these were the predecessors to the development of GM’s Voltec technology, which debuted in the Chevrolet Volt.
The Volt is a “series hybrid” that combines both a small ICE with a 355-V lithium-ion battery with cells from LG Chem and pack designed by GM and two electric motors. During the same period, Toyota began working on a system to hybridize their small cars. Similar to GM efforts with the EV1, Toyota designed a hybrid vehicle from the ground up. The Toyota Hybrid System (THS) they developed formed the basis for what has become the best-selling hybrid vehicle on the market today, the Toyota Prius. Toyota’s