Sanyo supplies the battery for the Ford Escape Hybrid car and just published a detailed article describing their efforts for Hybrid Electric Vehicle (HEV) batteries.

SANYO Electric started the development of HEV battery systems already back in 1997 and has been suppling it to Ford since 2004.

The battery system for Ford Motor's HEVs incorporates 250 size-D nickel-metal hydride batteries. In addition to being capable of high-power/long-life/high-quality, this battery system is required to have the mechanism to maintain the entire battery system in the optimal condition.

Ford Motor has sold 76,041 Escape Hybrid vehicles in the United States so far (September 2004 - May 2008).
More details on the Sanyo site.