Plugging Away

The fact that it’s at least a year before an automaker rolls a single plug-in vehicle onto a dealer lot is irrelevant. For GM and Toyota, the hard sell on who has the better battery blueprint has already started.

At the 2008 Society of Automotive Engineers (SAE) World Congress, Toyota made the case that plug-in hybrid electric vehicles (PHEVs) are the thriftier long-run choice for consumers because the cost of a larger battery pack needed for an all-electric-drive vehicle, like the Chevy Volt, overshadows its on-road benefits. At the 2009 SAE World Congress, GM appeared to return serve in presenting an SAE study examining the potential savings of extended range electric vehicles (EREVs), which are big on batteries, but only use the engine to generate electricity for longer driving range and not to power the wheels. GM’s study was based on National Household Travel Survey, which tracks the daily driving habits of nearly 60,000 drivers in both urban and suburban settings. The key finding is—all things being equal (same driving cycle and vehicle size)—an EREV with an 8-kWhr battery (the Volt’s will be 16-kWhr) will use 22% less gasoline and contribute 8% less CO2 than an 8-kWhr PHEV—based on 3.3-kW charging at home and (if you’re lucky enough) at work.

The larger the battery, argues GM, the bigger advantage for EREVs. For distances under 100 miles, or what 92% of Americans drive a day, an 8-kWhr EREV will use less than half the gasoline and emit less than one third of the CO2 of a 4-kWhr PHEV. “The travel survey told us where people will potentially charge and we examined battery size to match it,” says Pete Savagian, engineering director, GM Hybrid Powertrain Engineering. “It would be great to make the battery on the Volt smaller, but if we take the energy down we’re going to take the power and range down with it.”

When it comes to how drivers will charge their vehicles, the matter is less contentious. Most of the major players, from GM, Chrysler, Ford, Nissan, Toyota, and yes, Tesla, are in on board for the same conductive charging connectors standard, dubbed “J1772.” (Daimler has balked in favor of a European version.) The five-pronged J1772 connector, made by Yazaki, carries up to 240 V and 70 A from AC (home) to vehicle.