In the quest for a solution to the growing global transportation energy needs, plug-in hybrids have recently taken center stage. Plug-in hybrids, unlike the gas-electric hybrids currently on the market, can travel for extended ranges without using any gasoline. Yet, the emergence of plug-in hybrids depends on the viability of mass-manufactured lithium ion battery technologies. That technology may not be available for a decade or more, according to Dr. Menahem Anderman, a leading expert on advanced automobile batteries.
Speaking at the Society of Automotive Engineers 2007 Hybrid Symposium in San Diego in February, Dr. Anderman said, “The reliability of lithium ion technology for automotive applications is not proven.”
In a briefing to the U.S. Senate Committee on Energy and Natural Resources in January 2007, Dr. Anderman said the commercialization of plug-in hybrids with a gas-free range of 20 miles faces a long list of obstacles, including battery performance, longevity, reliability, and cost. “Pending significant improvements in battery technology, plug-in hybrids could possibly start making an impact in about 10 years,” he said.
The tentative quality of Dr. Anderman’s words—“could possibly start”—suggested that development of lithium ion batteries suitable for plug-in hybrids could require well more than a decade. However, many industry observers expect a much shorter timeframe for lithium ion batteries to show up in today’s hybrids, such as the Toyota Prius, which do not allow drivers to recharge batteries via the electric grid.
In Washington, Dr. Anderman characterized the primary differences between today’s hybrid batteries, and the next-generation battery technologies required for plug-ins:
- The plug-in battery will be about three to five times the size of today’s conventional hybrid batteries, essentially filling the cargo space of an average sedan. (Dr. Anderman described the space issue as a “showstopper” for plug-in application for sedans, unless the vehicle was “built from the ground up” to accommodate the extra batteries.)
- The weight of this battery will add 200 to 300 pounds to that of the car, which will adversely affect vehicle performance and efficiency.
- If the plug-in battery vehicle contains a lithium ion battery, to be given a full charge every night in a residential garage, there is a much more serious concern about hazardous failure than with the smaller batteries of conventional hybrids, which are always kept at an intermediate state of charge.
- The life of either battery technology, nickel metal hydride or lithium ion, in the plug-in application is not known. There is a significant risk that its life will be shorter than that of conventional hybrid car batteries.
- The cost of this plug-in battery (when assembled into packs) to carmakers, using present technology, will be three to five times the average cost of today’s hybrid batteries—around $5,000 to $7,000 per pack.
In an interview for HybridCars.com in January, Dr. Anderman also called into question the ability for battery makers to predict the performance of batteries over time. Tests can simulate the repeated charging and discharging of batteries, however, “you are trying to guess impact of calendar life,” he said. “To do 10 cycles per day for one year is not the same as one cycle a day for 10 years.” This uncertainty adds to the risk and cost that carmakers must be willing to accept before bringing a plug-in hybrid to market.
In the Senate briefing, Dr. Anderman once again emphasized the cost factors. “The manufacturing of high-volume, low-cost, and high-reliability lithium ion batteries for the portable [device] market is challenging, and established producers have paid dearly to move up the learning curve and down the cost curve,” he said. “The manufacturing of low-cost, high-power lithium ion batteries for hybrids is considerably more demanding.”