Machine Design

Assault and Batteries

Researchers at Sandia National Laboratories must hate batteries: They heat them to extreme temperatures, overcharge them, drive nails into them, and generally do whatever they can to destroy them.

The torture tests are part of the DOE-funded FreedomCAR program that is testing lithium-ion batteries for hybrid electricgasoline vehicles and plug-in hybrids.

Current hybrid vehicles run on gasoline and use nickel-metal hydride batteries to store energy for the electric motor. FreedomCAR hopes to replace those batteries with lithiumion versions that have six times the energy density of lead-acid batteries and two to three times the energy density of nickel-metal hydride batteries.

“Lithium-ion batteries in laptops and power tools have greatly improved over the past few years,” says Peter Roth, lead researcher for Sandia’s FreedomCAR battery efforts. “In fact, they have improved so much that we expect to see them in hybrids later this year and possibly in short-range plug-in hybrids within two years.”

The researchers test batteries to determine when and how they can fail or leak. They also study the stability of the materials, flameretardance, high-temperature integrity of separators between the cathode and anode, and other thermophysical properties.

Roth says some of the newer batteries, like the new lithium/ iron phosphate versions in hand-held power tools, are extremely resilient and less reactive when subjected to extreme conditions. Industry experts predict that plug-ins that can run 10 miles using only electricity are two to three years away while plug-ins that can run 40 miles are three to four years away.

The first hybrids using lithiumion batteries will be on the market later this year when Mercedes- Benz launches the S400 BlueHybrid. After that, it will launch the S300 Bluetec Hybrid, a diesel car with a lithium-ion battery. General Motors plans to introduce a 40-mile plug-in hybrid electric vehicle with lithium-ion batteries in 2010.

Sandia researcher Peter Roth prepares to blow up

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