Methodology for Emissions Measurement - Evaluation of the Battery Charge Level Influence on Hybrid Vehicle Emissions.

Due to the worldwide trends to develop new automotive technologies for vehicle emissions and fuel consumption reduction, and because PETROBRAS (Brazilian Oil Company) decided to act as an energy company, CENPES (PETROBRAS Research Centre) imported two hybrid electric vehicles (HEV) to study this technology. The main objective was to verify if Brazilian gasoline (which is blended with 25% ethanol) was adequate to use with hybrid electric vehicles.

Preliminary emissions tests with both vehicles, following the FTP-75 cycle, indicated a significant variation in the results, motivating further research to study the problem. It was verified that one of the main causes for this poor repeatability was the battery charge level of the hybrid system at the beginning of the emission tests. Based on this conclusion, CENPES studied ways to develop procedures that could guarantee the same initial conditions for the battery in emissions tests and also how battery charging system works.

This paper presents the results of the emission and fuel economy tests for one HEV tested with different battery charge levels. The FTP-75 emission tests were done on a chassis dynamometer using a HEV based on parallel hybrid technology. It is also proposed a procedure to run emission tests with this type of HEV with good repeatability.