High Energy Batteries for Hybrid Buses

Abstract

EnerDel batteries have already been employed successfully for electric vehicle (EV) applications. Compared to EV applications, hybrid electric vehicle (HEV) bus applications may be less stressful, but are still quite demanding, especially compared to battery applications for consumer products. This program evaluated EnerDel cell and pack system technologies with three different chemistries using real world HEV-Bus drive cycles recorded in three markets covering cold, hot, and mild climates. Cells were designed, developed, and fabricated using each of the following three chemistries: (1) Lithium nickel manganese cobalt oxide (NMC) - hard carbon (HC); (2) Lithium manganese oxide (LMO) - HC; and (3) LMO - lithium titanium oxide (LTO) cells. For each cell chemistry, battery pack systems integrated with an EnerDel battery management system (BMS) were successfully constructed with the following features: real time current monitoring, cell and pack voltage monitoring, cell and pack temperature monitoring, pack state of charge (SOC) reporting, cell balancing, and over voltage protection. These features are all necessary functions for real-world HEV-Bus applications. Drive cycle test data was collected for each of the three cell chemistries using real world drive profiles under hot, mild, and cold climate conditions representing cities like Houston, Seattle, and Minneapolis, respectively. We successfully tested the battery packs using real-world HEV-Bus drive profiles under these various climate conditions. The NMC-HC and LMO-HC based packs successfully completed the drive cycles, while the LMO-LTO based pack did not finish the preliminary testing for the drive cycles. It was concluded that the LMO-HC chemistry is optimal for the hot or mild climates, while the NMC-HC chemistry is optimal for the cold climate. In summary, the objectives were successfully accomplished at the conclusion of the project. This program provided technical data to DOE and the public for assessing EnerDel technology, and helps DOE to evaluate the merits of underlying technology. The successful completion of this program demonstrated the capability of EnerDel battery packs to satisfactorily supply all power and energy requirements of a real-world HEV-Bus drive profile. This program supports green solutions to metropolitan public transportation problems by demonstrating the effectiveness of EnerDel lithium ion batteries for HEV-Bus applications.