Toyota's top hybrid engineers say they are all for plug-ins, but they don't think the lithium-ion batteries they depend on will be ready to meet their stringent quality standards for several years. (They cannot resist a polite titter about spontaneously combusting laptop batteries.) Toyota is therefore likely to stick with the heavy and range-limited nickel-metal hydride battery for the third-generation Prius, due in 2009.

ECONOMIST: Hybrid cars: Beyond the Prius | The