New study finds that less is more with it comes to hybrid, plug-in batteries

A new study from Carnegie Mellon University has found that small batteries offer more benefits than large batteries in plug-in and hybrid vehicles.

Although most Americans typically associate "bigger" with "better", a new study from Carnegie Mellon University finds that plug-in and hybrid electric vehicles with small battery packs actually outperform vehicles with large battery packs in terms of emissions and reduced oil consumption.

The study found that while larger battery packs allow for a greater range, they are often inefficiently used. A larger battery pack means more weight (and costs) and also requires more energy to charge. The study also notes that larger batteries produce more emissions during the manufacturing process.

"Current government policy provides larger subsidies for vehicles with larger battery packs, assuming that larger is better," said Jeremy J. Michalek, an associate professor of engineering and public policy and mechanical engineering at CMU. "While larger battery packs allow plug-in vehicles to drive longer distances on electric power instead of gasoline, they are also expensive and heavy, they are underutilized when the battery capacity is larger than needed for a typical trip, they require more charging infrastructure and they produce more emissions during manufacturing."

Mikhail Chester, the report's co-author, explains that larger batteries could show increased benefits in the future if certain factors fall into place, but that small batteries still remain the best option.

"It's possible that in the future plug-in vehicles with large battery packs might offer the largest benefits at competitive costs if the right factors fall into place, including sufficiently low cost batteries, high gasoline prices, low emission electricity and long battery life," Chester said. "But such a future is not certain, and in the near term, HEVs and plug-in vehicles with small battery packs provide more emissions benefits and oil displacement benefits per dollar spent."

Carnegie Mellon is hopeful that the study will help influence future green vehicles incentive from Washington.