Conditioning Procedure for HEV's Batteries Applied to Different Emissions and Fuel Economy Cycles

The automobile industry has developed and marketed hybrid electric vehicles (HEV) internationally for over 10 years. The presence of batteries in these vehicles poses difficulties for their approval in laboratory trials. The difference between the initial and final battery state of charge changes the energy balance measured in the tests, affecting the emissions and fuel economy levels. Two proposals have emerged to address this problem. One is described in ISO 23274, which consists in determining and applying a correction factor to the emissions and fuel economy results. This factor is based on the difference between the initial and final battery state of charge after the test. The other is described by SAE J1711 which consists in conditioning the battery, in order to equal the state of charge level at the end and start of the test, avoiding the factor recalculation. The main objective of this paper is to study the energy flow in the batteries during the tests and, based on this study, to propose a new procedure for its conditioning. The SAE J1711 proposes the resumption of the old proposal FTP75 cycle with four stages in order to condition the battery. However, it is possible, also, to achieve the same effect using other cycles. In addition to theoretical studies, experimental tests were performed with three hybrid electric vehicles using FTP75 cycle (three phases) and European cycle ECE-1505.