Although car companies say they’re waiting for better battery technology before they mass-market plug-in hybrids, that doesn’t sit well with drivers like Marc Geller of San Francisco, a PV systems salesman who co-founded the nonprofit group Plug In America. The nickel-metal hydride (NiMH) batteries in Geller’s all-electric 2002 Toyota RAV4-EV give the compact SUV plenty of power, take him all over the Bay Area, and are expected to last the life of the car, based on utility company fleet tests.
Long before unveiling its “new” plug-in hybrid Volt, GM displayed a prototype plug-in hybrid version of its EV1 electric car at auto shows in the 1990s. The EV1 plug-in hybrid could go 25 miles on electricity stored in NiMH batteries before the gasoline engine turned on, which would then extend the range to 320 miles. Professor Andrew Frank at the University of California at Davis collaborated with the NiMH battery company Energy Conversion Devices in 1998 to convert an early Toyota Prius to a plug-in hybrid, with similar results. Toyota will be testing their plug-in Prius in Japan, and will be delivering one each to UC–Berkeley and UC–Irvine. The cars are expected to have only a 7- to 8-mile range on their NiMH batteries, but if the cars move into production, more advanced batteries are likely to be used.
People who have been driving electric cars for years using NiMH batteries suggest that the car companies are stalling by insisting on Li-ion batteries. The major auto manufacturers say that Li-ion batteries are preferable because they store more energy in less space, so fewer batteries are needed and less weight is added to the vehicle. It’s unclear, however, whether Li-ion batteries will last as long as expected in conventional warranties. California state regulators are considering modifying warranty requirements for hybrids, which could jump-start production of plug-in cars with Li-ion batteries. Or, as GM’s CEO Robert Lutz acknowledged in a recent interview on PodTech.net, if Li-ion doesn’t work out, “we might use NiMH for plug-in hybrids after all.”