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Internal combustion engine (ICE) cold-start is an issue that occurs either in conventional and hybrid powertrains before the ICE reaches its normal operation temperature, affecting both fuel consumption due to higher heat losses, and pollutant emissions due to low catalytic converter temperatures. The study of cold start emissions on conventional powertrains has been extensively addressed, although typically under laboratorial conditions, however studies addressing the impact of this phenomenon on hybrid powertrains is still reduced. Hybrid electric (HEV) and plug-in hybrid electric (PHEV) vehicles usually incorporate technologies to manage the battery and ICE power supply leading to ICE on/off operation under regular driving, which can result in a decrease on catalytic converter efficiency (due to cooling).

Plug-in hybrid vehicles have complex energy management and are very influenced by charging behavior. Since current on-road data analysis methodologies do not take into consideration propulsion management, it is difficult to correctly estimate their energy and emissions impacts. This paper presents a methodology (ABCD Method) based only on dynamic data to assess the battery state of charge, identifying, second by second, which propulsion source is working and estimating the correspondent energy consumption, pollutant gas emissions and utility factor. Using a Portable Emission Measurement System, this methodology was developed based on real driving data obtained on four trips in two different PHEV. Excellent correlations were obtained between the estimated and measured SOC (R2>0.98). The ABCD Method uses a generic algorithm to allocate points of different propulsion combinations, correctly identifying the energy source used in over 81.9% of trip points.