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Lithium-based battery technology offers performance advantages over traditional battery technologies at the cost of increased monitoring and controls overhead. Multiple-cell Lead-Acid battery packs can be equalized by a controlled overcharge, eliminating the need to periodically adjust individual cells to match the rest of the pack. Lithium-based based batteries cannot be equalized by an overcharge, so alternative methods are required. This paper discusses several cell-balancing methodologies. Active cell balancing methods remove charge from one or more high cells and deliver the charge to one or more low cells. Dissipative techniques find the high cells in the pack, and remove excess energy through a resistive element until their charges match the low cells. This paper presents the theory of charge balancing techniques and the advantages and disadvantages of the presented methods.

An electromechanical gear is presented along with design examples utilizing the electromechanical gear in hybrid electric vehicle drive trains. The designs feature the electromechanical gear (the Transmotor) in place of traditional mechanical transmissions and/or gearing mechanisms. The transmotor is an electric motor suspended by its shafts, in which both the stator and the rotor are allowed to rotate freely. The motor thus can provide positive or negative rotational energy to its shafts by either consuming or generating electrical energy. A design example is included in which the transmotor is installed on the output shaft of an internal combustion engine. In this arrangement the transmotor can either increase or decrease shaft speed by applying or generating electrical power, allowing the ICE to operate with a constant speed.

The effect on vehicle performance of extending the constant power operating mode of electric drive motors for electric and hybrid vehicles is presented in this paper. Modern electric and hybrid vehicle designers have the selection of several technologies to choose from when selecting an electric drive motor. Each motor technology exhibits a particular torque vs. speed characteristic. Many of these technologies, most notably the switched reluctance machine, have capitalized on iron and copper utilization, extending their useful speed range. However, the extended speed capabilities of these motor drives have vehicle performance consequences. It is presented that vehicle performance is affected by changing the torque-speed characteristics of the drive motor. The extended constant power speed range motor can have smaller rated power than otherwise but suffer high speed passing performance.