Ni-MH battery pack

Behind a pair of plastic covers, you'll find the NiMH battery pack that powers the Hybrid Synergy Drive system -- a 244.8-volt bank of cells that adds 150 pounds of mass to the Avalon -- as well as the standard 12-volt accessory battery, which has been relocated to the trunk to make room in the engine bay. The Hybrid battery pack eliminates the rear-seat pass-through for long items and eats up a few cubic feet of cargo space.