Lithion Batteries on a Mars Mission

Lithium-ion batteries onboard the Mars Explorer Rovers (MERs) were built by Lithion Inc. of Pawcatuck, Connecticut, a provider of high energy density batteries for aerospace and marine applications, and a division of Yardney Technical Products Inc.

The primary objectives for the MERs were to explore the surface of the planet for at least 90 Martian days. The Spirit Rover has survived 181 days past it’s “90-day warranty” and Opportunity has survived 161 days past its’ similar warranty. After almost nine months of successful operations, NASA officials have decided to fund the project through March 2005.

The two 28V, 8Ah Li-ion batteries are used to provide power to the MER during the Martian night, and to provide peak power to the MER during the day when several scientific instruments are being used. The Li-ion batteries have maintained peak performance, and the mission planners have optimized the charging/discharging cycles to allow the vehicles to continue to roam the planet. Lithion’s power/energy margin estimates were revised well past the 60-plus days initially projected for margin.

“We are very pleased with the performance of our batteries. We knew the constraints on this mission were subject to the severe weather we would encounter once we moved out of the summer months,” says Lithion Vice President and General Manager Vince Yevoli. “With the ingenuity of the NASA mission planners, we’ve been able to get a good charge on the battery. That’s all they need to get us through the winter. My bet is we’ll still be there in the spring!”