Test Analysis of Traction Battery Peak Power

The test process of electric vehicles (EVs) traction battery peak power is analyzed in detail. Aimed at a special “traction” design of versatile battery—HORIZON~ C~2M Battery, the features are introduced. According to the peak power test schedule, the test parameters of HORIZON~ C~2M Battery are calculated and the charging and discharging experiments are carried out. The sustained (30 s) discharge power capability of battery at 2/3 of its open circuit voltage at each of various depths of discharge is determined. The dynamic internal resistance under peak power test is established. Considering the temperature impact during discharging, the peak power capability at each of various depths of discharge is corrected. The correctness of peak power test is validated by combining theory analysis with test results.

Cycle life prediction of traction battery based on degradation data

The traction battery cycle life prediction method using performance degradation data was proposed. The example battery was a commercialized lithium-ion cell with LiMn2O4/Graphite cell system. The capacity faded with cycle number follows a traction function path. Two cycle life predicting models were established. The possible cycle life was extrapolated, which follows normal distribution well. The distribution parameters were estimated and the battery reliability was evaluated. The models＇ precision was validated and the effect of the cycle number on the predicting precision was analysed. The cycle life models and reliability evaluation method resolved the difficulty of battery life appraisal, such as long period and high cost.

Comparative Study on Traction Battery Charging Strategies from the Perspective of Material Structure

The service life of an electric vehicle is,to some extent,determined by the life of the traction battery.A good charging strat-egy has an important impact on improving the cycle life of the lithium-ion battery.Here,this paper presents a comparative study on the cycle life and material structure stability of lithium-ion batteries,based on typical charging strategies currently applied in the market,such as constant current charging,constant current and constant voltage charging,multi-stage constant current charging,variable current intermittent charging,and pulse charging.Compared with the reference charging strategy,the charging capacity of multi-stage constant current charging reaches 88%.Moreover,the charging time is reduced by 69%,and the capacity retention rate after 500 cycles is 93.3%.Through CT,XRD,SEM,and Raman spectroscopy analysis,it is confirmed that the smaller the damage caused by this charging strategy to the overall structure of the battery and the layered structure and particle size of the positive electrode material,the higher the capacity retention rate is.This work facilitates the development of a better charging strategy for a lithium-ion battery from the perspective of material structure.

Experimental Study of Energy Consumption Variation in Recurring Driving Trips

With a growing consumer market of battery electric vehicles, customers＇ demand for technology and features is on the rise. The range and, to a certain extent, the range estimation will play a key factor in customers＇ purchase decisions. In order to guarantee a precise range estimation over the usage life of battery electric vehicles, a method is presented that combines adaptive filter algorithms with statistical approaches. The statistical approach uses recurring driving cycles over the lifetime in order to derive the aging status of the traction battery. It is implied that the variance of the energy usage of these driving cycles is within certain bounds. This fact should be proven by an experimental case study. The dataset used in this paper is open to the public.

Progress review of US-China joint research on advanced technologies for plug-in electric vehicles

The United States and China are the world's largest automobile markets and oil consumers, and both face a severe challenge to conserve energy and reduce tailpipe emissions. Thus, both countries urgently need to transform conventional internal combustion engines to electrified powertrains. Targeting the advanced core technologies of plug-in electric vehicles(PEVs), a joint research collaboration between China and the US, called the "Clean Vehicle Consortium"(CVC), was set up in 2010. Six years of collaboration on PEV technologies has resulted in significant progress in three technical areas. Based on CVC publications,we review herein the progress made by the CVC research efforts on three key advanced PEV technologies. This includes the development of a safe battery with an energy density of 260 W h kg^(-1) and a systematic method for designing safe traction battery systems. Thus, a breakthrough in high power density and efficient traction motor systems has occurred. In addition to discussing advanced electric-drive powertrains, we also discuss global energy management strategies that aim to improve PEV energy efficiency. This discussion covers scientific and comprehensive analysis methods to analyze energy systems, which include costbenefit analyses of plug-in hybrid electric vehicles, life-cycle assessments for evaluating vehicle emissions, and PEV-ownership projections.