High-Power Battery Testing Procedures and Analytical Methodologies for HEV's

Motloch, Chester G.; Christophersen, Jon P.; Belt, Jeffrey R.; Wright, R. B.; Hunt, Gary L.; Sutula, Raymond A.; Duong, Tien Q.; Tartamella, Thomas J.; Haskins, H. J.; Miller, Ted

doi:10.4271/2002-01-1950

Cited by 59 publications

(34 citation statements)

References 2 publications

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“…• C to 40 • C. 3 Capacity and power degradation is also accelerated at elevated temperatures. [4][5][6][7][8][9] The lithium iron phosphate (LFP) cell chemistry is gaining wide acceptance in electric vehicle applications.…”

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confidence: 99%

Thermal Effect of Cooling the Cathode Grid Tabs of a Lithium-Ion Pouch Cell

Bazinski

Wang

2014

J. Electrochem. Soc.

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Infrared thermography shows that the joint between the cathode grid stack and the cell tab is a source of Joule heating within a lithium-ion pouch cell. This can exacerbate thermal gradients within the cell core if the C-rate is sufficiently high. This paper studies the heat generated at the cathode tab joint of a 14Ah lithium iron phosphate (LFP) pouch cell. The heat generation was quantified by using an energy balance equation and the average heat transfer coefficient was calculated by modeling the cell as an isothermal vertical plate in natural convection. The influence of this heat on the cell's thermal gradients was studied during a 3C and 8C rate of discharge. It has been found that removal of this heat at its source can appreciably lower the overall average surface temperature of the cell. However, at a 3C rate discharge, the removal of this heat can induce a greater thermal gradient within the cell core. At an 8C rate of discharge, there is a minimal improvement in the temperature gradient. As a result, a thermal management system which incorporates cathode tab heat removal would most likely be an ineffective design feature. Maintaining uniformity of temperature between cells is an important factor in the thermal management of lithium-ion batteries. It is desirable for this variation to be in a tight range.1 Rugh et.al. stated that temperature gradients should be kept to less than 3• C to 4• C throughout the battery pack.2 Failure to meet this criterion has a direct effect on decreasing the battery pack life. In addition, they also advocate an operating temperature range of 15• C to 35• C for the pack. Excursions beyond this range have repercussions as well. It has been found that the lifespan for a lithium-ion cell is reduced by approximately 2 months for every degree of temperature rise while operating in a temperature range of 30• C to 40 • C. 3 Capacity and power degradation is also accelerated at elevated temperatures. 4-9The lithium iron phosphate (LFP) cell chemistry is gaining wide acceptance in electric vehicle applications.10 Its inherent ability to tolerate abusive conditions and resist thermal runaway is especially attractive to battery pack designers. Battery manufacturers have responded by offering high capacity cells in a pouch format. This format affords better packaging efficiency and offers a very favorable area-tovolume ratio to facilitate thermal management. As a result, this work uses a high capacity LFP pouch cell.The temperature near the cathode terminal of a pouch cell is consistently higher than that at the anode, due to differences in the thermal conductivities of the metals used as current collectors. This is true regardless of the particular lithium-based electrochemistry being used.

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confidence: 99%

Thermal Effect of Cooling the Cathode Grid Tabs of a Lithium-Ion Pouch Cell

Bazinski

Wang

2014

J. Electrochem. Soc.

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“…(1) t is a lower triangular matrix with coefficients a (1) tij defined by (9) and (10) T is an upper triangular matrix with coefficients a (2) tij defined by (13) and (14) for reverse coolant flow.…”

Section: Complete Averaged State-space Model Of N-cell Mlcmentioning

confidence: 99%

Performance evaluation of Multilevel Converter based cell balancer with reciprocating air flow

Altaf

Johannesson

Egardt

2012

2012 IEEE Vehicle Power and Propulsion Conference

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Abstract-The modeling and design of an active battery cell balancing system using Multilevel Converter (MLC) for EV/HEV/PHEV is studied under unidirectional as well as reciprocating air flow. The MLC allows to independently switch ON/OFF each battery cell in a battery pack. The optimal policy (OP ) exploiting this extra degree-of-freedom can achieve both temperature and state-of-charge (SoC) balancing among the cells. The OP is calculated as the solution to a convex optimization problem based on the assumption of perfect state information and future driving. This study has shown that OP gives significant benefit in terms of reduction in temperature and SoC deviations, especially under parameter variations, compared to uniformly using all the cells. It is also shown that using reciprocating flow for OP gives no significant benefit. Thus, reciprocating flow is redundant for MLC-based active cell balancing system when operated using OP .

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“…The lifetime of batteries is also adversely affected when operating at high temperature conditions [15][16][17][18]. Motloch, et al [19] states that for every 1 °C increase of cell temperature the lifetime of a Li-ion battery reduces by approximately two months in an operating temperature range of 30 to 40 °C. As another example: experimental studies conducted in America have shown that for Electric Vehicles (EVs) mileage declined approximately 60% when the ambient temperature dropped below −6 °C and the mileage also dropped 33% when the ambient temperature exceeded 35 °C [20,21].…”

Section: Introductionmentioning

confidence: 99%

Theoretical Modelling Methods for Thermal Management of Batteries

Shabani¹,

Biju²

2015

Energies

108

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Abstract:The main challenge associated with renewable energy generation is the intermittency of the renewable source of power. Because of this, back-up generation sources fuelled by fossil fuels are required. In stationary applications whether it is a back-up diesel generator or connection to the grid, these systems are yet to be truly emissions-free. One solution to the problem is the utilisation of electrochemical energy storage systems (ESS) to store the excess renewable energy and then reusing this energy when the renewable energy source is insufficient to meet the demand. The performance of an ESS amongst other things is affected by the design, materials used and the operating temperature of the system. The operating temperature is critical since operating an ESS at low ambient temperatures affects its capacity and charge acceptance while operating the ESS at high ambient temperatures affects its lifetime and suggests safety risks. Safety risks are magnified in renewable energy storage applications given the scale of the ESS required to meet the energy demand. This necessity has propelled significant effort to model the thermal behaviour of ESS. Understanding and modelling the thermal behaviour of these systems is a crucial consideration before designing an efficient thermal management system that would operate safely and extend the lifetime of the ESS. This is vital in order to eliminate intermittency and add value to renewable sources of power. This paper concentrates on reviewing theoretical approaches used to simulate the operating temperatures of ESS and the subsequent endeavours of modelling thermal management systems for these systems. The intent of this review is to present some of the different methods of modelling the thermal behaviour of ESS highlighting the advantages and disadvantages of each approach. OPEN ACCESSEnergies 2015, 8 10154

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High-Power Battery Testing Procedures and Analytical Methodologies for HEV's

Cited by 59 publications

References 2 publications

Thermal Effect of Cooling the Cathode Grid Tabs of a Lithium-Ion Pouch Cell

Thermal Effect of Cooling the Cathode Grid Tabs of a Lithium-Ion Pouch Cell

Performance evaluation of Multilevel Converter based cell balancer with reciprocating air flow

Theoretical Modelling Methods for Thermal Management of Batteries

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