As part of the Midterm Evaluation of the 2017-2025 Light-duty Vehicle Greenhouse Gas Standards, the U.S. Environmental Protection Agency (EPA) developed simulation models for studying the effectiveness of stop-start technology for reducing CO 2 emissions from light-duty vehicles. Stop-start technology is widespread in Europe due to high fuel prices and due to stringent EU CO2 emissions standards beginning in 2012. Stop-start has recently appeared as a standard equipment option on high-volume vehicles like the Chevrolet Malibu, Ford Fusion, Chrysler 200, Jeep Cherokee, and Ram 1500 truck. EPA has included stop-start technology in its assessment of CO 2-reducing technologies available for compliance with the standards. Simulation and modeling of this technology requires a suitable model of the battery. The introduction of stop-start has stimulated development of 12-volt battery systems capable of providing the enhanced performance and cycle life durability that it requires. Much of this activity has involved advanced lithium-ion chemistries, variations of lead-acid chemistries, such as absorbed-glass-mat (AGM) designs, and lead-carbon formulations. EPA tested several AGM batteries that are used in OEM start-stop systems. The purpose of this testing was to develop an equivalent circuit model for integration into EPA's ALPHA vehicle simulation model. Testing was performed at the Battery Test Facility (BTF) at the U.S. Environmental Protection Agency (EPA) National Vehicle and Fuel Emissions Laboratory (NVFEL) in Ann Arbor, Michigan. The Duracell batteries referenced are model number SLI49AGM with a rating of 92 Ah and the X2 Power batteries referenced are model number SLI34-78AGMDP with a rating of 68 Ah. Both batteries are 6 cell 12 volt using AGM technology. For compatibility with the voltage specifications of the BTF equipment, tests were performed on two batteries connected in series (nominal 24 volts). This paper presents the development and validation of the lead-acid battery model. The battery model is a standard equivalent circuit model with two Resistance-Capacitance (RC) blocks. Resistances and capacitances were calculated using test data from a Duracell 92Ah lead-acid battery which is aftermarket equipment for the Chevrolet Malibu. The lead-acid battery library in the ALPHA model was validated with data obtained from Argonne National Laboratory (ANL) from their chassis dynamometer testing of the 2010 Mazda 3 Hatchback i-Stop [9] and 2010 VW Golf TDI Diesel Bluemotion [10]. The simulated battery voltages, currents, and state of charge (SOC) are in excellent agreement with the vehicle test data on a number of drive schedules.
T he Advanced Light-Duty Powertrain and Hybrid Analysis tool (ALPHA) was created by EPA to evaluate the Greenhouse Gas (GHG) emissions of Light-Duty (LD) vehicles. ALPHA is a physics-based, forward-looking, full vehicle computer simulator capable of analyzing various vehicle types combined with diferent powertrain technologies. Te ALPHA desktop application was developed using MATLAB/Simulink. Te ALPHA tool was used to evaluate technology efectiveness and of-cycle technologies such as air-conditioning, electrical load reduction technology and road load reduction technologies of conventional, non-hybrid vehicles for the Midterm Evaluation of the 2017-2025 LD GHG rule by the U.S. Environmental Protection Agency (EPA) Ofce of Transportation and Air Quality (OTAQ). Tis paper presents controls development, modeling results, and model validation for simulations of a vehicle with a 48 V Belt Integrated Starter Generator (BISG) mild hybrid electric vehicle and an initial model design for a 48 V inline on-axis P2-confguration mild hybrid electric vehicle. Both confgurations were modeled with a MATLAB/Simulink/Statefow tool, which has been integrated into EPA's ALPHA vehicle model and was also used to model components within Gamma Technology GT-DRIVE simulations. Te mild hybrid electric vehicle model was validated using vehicle data obtained from Argonne National Laboratory (ANL) chassis dynamometer tests of a 2013 Chevrolet Malibu Eco 115 V 15 kW BISG mild hybrid electric vehicle. Te simulated fuel economy, engine torque/speed, motor torque/speed, engine on-of controls, battery voltage, current, and State of Charge (SOC) were all in good agreement with the vehicle test data on a number of drive schedules. Te developed 48 V mild hybrid electric vehicle model can be used to estimate the GHG emissions and fuel economy of 48 V mild hybrid electric vehicles over the EPA regulatory drive cycles and to estimate of-cycle GHG emissions. Te 48 V mild hybrid electric vehicle model will be further validated with additional 48 V mild hybrid electric vehicle test data in the future as more vehicle models become available. EPA has included 48 V BISG mild hybrid electric vehicle technology in its assessment of CO2-reducing technologies available for compliance with U.S. GHG standards.
A Battery Test Facility (BTF) has been constructed at United States Environmental Protection Agency (EPA) to test various automotive battery packs for HEV, PHEV, and EV vehicles. Battery pack tests were performed in the BTF using a battery cycler, testing controllers, battery pack cooler, and a temperature controlled chamber. For e-machine testing and HEV power pack component testing, a variety of different battery packs are needed to power these devices to simulate in-vehicle conditions. For in-house e-machine testing and development, it is cost prohibitive to purchase a variety of battery packs, and also very time-consuming to interpret the battery management systems, CAN signals, and other interfaces for different vehicle manufacturers. Therefore, there is a need to accurately emulate battery pack voltage, power, current, State of Charge (SOC), etc. for testing e-machines as well as performing real-time HIL (Hardware-In-Loop) vehicle simulations by having the ability to instantly select a cell chemistry along with battery pack configuration such as cell capacity, number of cells in series/parallel, coolant type, etc. This paper presents lithium-ion battery pack HIL development and validation integrated into the EPA Battery Test Facility. The battery pack HIL model consists of lithium-ion cell chemistries, thermal characteristics, battery management system (BMS), and power limit controls. The HIL model of lithium-ion battery pack was validated by simultaneously running a real lithium-ion battery pack with Nissan Leaf EV and GM Volt Range Extended Vehicle power profiles to the battery cycler in the BTF. The emulated battery voltages, currents, SOC, and battery pack temperatures are in excellent agreement with battery pack test data on FTP UDDS, highway (HWFET) and US06 drive schedules.
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