Heat and mass transfer modeling and investigation of multiple LiFePO 4 /graphite batteries in a pack at low C-rates with water-cooling S. Panchal a,⇑ , M. Haji Akhoundzadehr b,c , K. Raahemifar c , M. Fowler b , R. Fraser a a Mechanical and Mechatronic Engineering Department, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada b Chemical Engineering Departments, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada c Electrical and Computer Engineering Departments, Ryerson University, 350 Victoria St, Toronto, ON M5B 2K3, Canada article info Article history: Received 18 October 2018 Received in revised form 11 January 2019 Accepted 17 January 2019 Keywords: LIB pack Mathematical modeling Heat and mass transfer Temperature field Voltage field Temperature control system abstract Li-ion batteries (LIBs) are found to be deep spots in the Electric Vehicles (EVs) as well as Hybrid Electric Vehicles (HEVs) application. Combination of such high capacity LIBs in large serial-parallel configurations have been wrapped up with serious problems such as safety, durability, cost, and uniformity, which are imposing limitations on this broad application. A narrow area of these limitations, in which LIBs should operate safely and reliably, is the essential requirement of an effective control-thermal management sce- nario. In this paper, we examined the heat and mass transfer (temperature and mass flow rate of water) field as well as voltage profiles for a 20 Ah Graphite/LiFePO 4 LIB pack at low currents of 20 A (1 C) and 40 A (2 C) with the selected ambient conditions using unique water-cooling methods with 35 °C, 25 °C, 15 °C, and 5 °C. This gives significant data information for the thermal behavior of LIB packs to design the temperature control (or thermal management) systems and develop an empirical voltage-thermal estimation model. In such manner, 3 prismatic LIBs with 20 Ah nominal capacity are arranged in a series with 4 micro-channel cooling plates placed within cells. There are six evenly placed thermocouples on the surface of each of these 3 battery cells used to extract time dependent temperatures. To make the data compatible for EV/HEV application, we developed a modified exponential-polynomial equivalent circuit model to simulate the temperature and voltage field. Outputs of the simulations are compared with the test data with specified C-rates and ambient conditions. The results demonstrate that increasing discharge currents and ambient conditions result in an increased surface temperature at 3 spots; close to the ve electrode, close to the +ve electrode, and near the middle part of the LIB cell. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction Powertrain electrification has recently established the ideas of the Plug-In Hybrid, Hybrid, and Electric Vehicles (PHEVs, HEVs, and EVs). These vehicles have been acquired an extensive attention since the main target in implementing of their powertrains is diminishing fuel consumption, as well as Greenhouse Gas (GHG) emission [1,2]. However, the most difficult segments in these efficient powertrains are their energy storage source. For those powertrains utilizing batteries as the main power source, Lithium-Ion (Li-Ion) batteries (LIBs) has shown compromising due to some specifications. They can generate high specific ener- gies at high power density [3,4]. These types of batteries can also supply large range of voltage (nominal voltage) along with a lower release rate [5]. Although, the cycle-life in Li-Ion batteries are so long, what has made them a good choice for a hybrid powertrain is that they have not observed any serious memory effect reported in these battery types [6]. There are five different sublayers in a LIB cell, which are ve electrode (anode), ve current collector, separator, +ve electrode (cathode), and +ve current collector. Several studies in literature are there, which perused the dynamic of a negative electrode, but only a few considered the response of positive sublayers. Typ- ically, there are four types of positive electrodes [7,8]. Metal with olivine structure, like the lithium-iron phosphate (LFP or LiFePO 4 ) [9]; metal electrodes with three dimensional spinal structures like the lithium nickel manganese cobalt oxide (NMC or LiNiMnCoO 2 ) [10]; lithium manganese oxide (LiMn 2 O 4 ); and also layered struc- ture metal oxide, like lithium cobalt oxide (LCO or LiCoO 2 ) [11]. The electrolyte may have material called liquid, polymer or solid. The charge and discharge mechanism and the line diagram of a LIB (with Graphite/LiFePO 4 as anode/cathode) with a separator within two terminals is introduced in Fig. 1. https://doi.org/10.1016/j.ijheatmasstransfer.2019.01.076 0017-9310/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: satyam.panchal@uwaterloo.ca (S. Panchal). International Journal of Heat and Mass Transfer 135 (2019) 368–377 Contents lists available at ScienceDirect International Journal of Heat and Mass Transfer journal homepage: www.elsevier.com/locate/ijhmt