Mike, Link info here "The Green Goat hybrid locomotives, by contrast, generate the tractive equivalent of 2,240 hp by combining a Caterpillar C9 8.8-liter, inline 6-cylinder diesel engine with a large bank of valve-regulated lead acid batteries. The 600V battery bank, specifically designed by RailPower, is maintenance free, has a long battery life, and high round trip efficiency. The added weight of the lead acid bank helps to improve the tractive effort or “pull.” This is a different situation than the auto industry where weight is a major issue."