Advanced Automotive Technology: Visions of a Super-Efficient Family Car

Battery Characteristics.

For this discussion, batteries have been divided into four thematic groups: lead acid, alkaline,

high temperature, and solid electrolyte. Various battery designs have been examined that would

fall under the latter three types, and obtaining comprehensive data on their current development

status and characteristics is challenging; a listing of the various types under development and their

developers is given in table 3-11. The discussion focuses on batteries that are potential winners

according to the current consensus, but it should be noted that the list of “winners” has changed

considerably during the last five years. For example, in 1991, the nickel-iron and sodium-sulfur

batteries were considered the most promising, but are no longer the leading contenders.

Lead acid

Lead acid batteries have been in existence for decades, and more advanced traction batteries

with improved specific power and energy, as well as durability, are under development. Delco

Remy’s VRLA battery is perhaps is the most advanced battery commercially available (though in

limited quantity), and it has claimed the following characteristics per battery module: a specific

energy of 35 Wh/kg, specific power of 210 W/kg (filly charged) and 150 W/kg at 20 percent

charge, and over 800 cycles of life at 50 percent DoD. Delco also offers a “battery package”

including fill thermal and electrical management. An entire 312V system with 26 modules and

battery management has a net specific energy of 30.5 Wh/kg.^69

Other recent developments include the woven grid pseudo-bipolar lead acid battery from

Horizon, which has a demonstrated specific energy of 42 Wh/kg and peak power of 500 W/kg at

fill charge and 300 W/kg at 80 percent DoD at the cell level. Horizon claims life in excess of 900

cycles at C/2 and has begun delivery of complete batteries from a pilot production plant.^70

Horizon anticipates additional improvements to specific energy levels over 48 Wh/kg at the

module level, and expects other benefits, such as fast charging, owing to the batteries’ low internal

resistance.

Bipolar lead acid batteries under development offer even higher power densities and energy

densities than the Horizon battery, with specific power of 900 W/kg and specific energy of 47

Wh/kg demonstrated by ARIAS Research at the module level.^71 The traditional problem with

bipolar batteries has been with corrosion at the electrode interfaces, and it is not yet clear whether

this problem has been solved over the life of the batteries. Nevertheless, the new designs show

promise in providing significant improvements in power and energy density, but providing

reasonable life may still be a serious problem.

Alkaline Systems

The three most successful candidates in this category are nickel-cadmium, nickel-iron and

nickel-metal hydride. Nickel-cadmium (Ni-Cd) batteries are available commercially, but the major

69 Ibid

70 Ibid

71 David Harbaugh, "The Role of the SBLA Battery in Meeting California’s Clean Air Act Goals," paper presented at the 12th International EV

Symposium, December 1994.