Short and long term energy source technologies for electrically-heated catalysts

A consortium of six companies formed by Southwest Research Institute conducted an investigation into alternative electric power supplies for electrically heated catalysts (EHCs). Previous studies showed that due to their high power and energy requirements upon engine start, battery-powered EHCs would cause premature failure of common Pb-acid batteries. This project identified and characterized several alternative electric energy sources. Production starting, lighting, and ignition (SLI) batteries were evaluated along with Pb-acid electric vehicle batteries, nickel-cadmium aircraft batteries, prototype ultracapacitors, and a modified alternator. Battery Council International and US Advanced Battery Consortium test methods were employed where applicable. Evaluations included ambient and low-temperature (~18°C) constant-current discharge characterization, low-temperature peak-power determination, self-discharge, and passenger car Federal Test Procedure (FTP) emissions and fuel economy. As demonstrated by discharge-energy and peak-power tests, some EV batteries may have potential for the EHC/SLI application. Others appeared to be poorly suited due to low-temperature problems. The best low-temperature performance was observed with ultracapacitors. These units were also the least to be affected by the power versus energy trade-off. The problems with these prototype storage units were high cost and self-discharge rate. Alternator power for EHCs as an alternative to energy storage devices was successfully demonstrated on a vehicle. Power produced was a linear function of engine speed and EHC load. High-voltage switching devices will be necessary for successful use of alternator power on EHCs. A fuel economy penalty was expected, but not observed during the FTP vehicle demonstration