The heat generation rate of nickel-metal hydride battery during charging/discharging
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The heat generation rate of nickel-metal hydride battery during charging/discharging Kaizheng Fang • Shi Chen • Daobin Mu Jianhong Liu • Wushou Zhang
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Received: 22 May 2012 / Accepted: 16 July 2012 / Published online: 21 August 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract The heat generation rate of nickel-metal hydride battery is investigated during charging/discharging in this study. The heat capacity of 8 Ah cylindrical Ni-MH battery is measured using a large-scale calorimeter. An accelerating rate calorimeter is employed to provide an adiabatic environment for the battery. The generation rates of reaction heat, polarization heat, and combination heat are calculated through curve fitting. Results show that there exits a linear relationship between each generation rate of the three heat items and the charging/discharging currents. It is suggested that the ohm internal resistance of the battery needs to be as low as possible for reducing the ohm heat. In addition, it is better to avoid overcharging in the higher rate of 5 C for battery safety. Keywords Nickel-metal hydride battery Heat generation rate Heat capacity Adiabatic environment Charging/discharging
Introduction As electric vehicles (EV) are expected to partly replace traditional fuel automobiles in the near future, power batteries used in EV are paid on more and more concerns [1].
Besides the electrochemical performance, battery’s thermal behavior is also extensively investigated so as to enhance battery safety. Wu et al. [2] employed a two-dimensional transient thermal model to study the heat dissipation of NiMH battery. Sato and Yagi [3] analyzed the items of heat generated in Ni-MH battery. Yang et al. [4] measured the heat generated in Ni-MH battery using a microcalorimeter. Our previous study [5] studied the thermal behavior of Ni-MH battery during charging at a wide range of ambient temperatures. Though Ni-MH battery is safer than other batteries for the use in EV [6–8], overmuch heat generated during the charging/discharging process still has influence on its safety performance. The total heat includes reaction heat, polarization heat, ohm heat, and combination heat [3]. They work together causing battery temperature rise, but, it is unclear that which item dominates in the total heat. Few of reports are also found on the quantitative study of the four heat items. To modify the thermal safety of the battery effectively, this study investigates the generation rates of various heat during charging/discharging. It is desirable to clarify the thermal behavior of the battery through analyzing the contribution of each heat item to the total heat quantitatively.
Experimental K. Fang S. Chen D. Mu (&) J. Liu Beijing Key Laboratory of Environmental Science and Engineering, School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100081, China e-mail: [email protected] W. Zhang Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
D-type nickel-metal hydride battery with a no
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