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Efficient thermal management of lithium-ion battery, working under extremely rapid charging-discharging, is of widespread interest to avoid the battery degradation due to temperature rise, resulting in the enhanced lifespan. Herein, thermal management of lithium-ion battery has been performed via a liquid cooling theoretical model integrated with thermoelectric model of battery packs and single-phase heat transfer. Aiming to alleviate the battery temperature fluctuation by automatically manipulating the flow rate of working fluid, a nominal model-free controller, i.e., fuzzy logic controller is designed. An optimized on-off controller based on pump speed optimization is introduced to serve as the comparative controller. Thermal control simulations are conducted under regular operating and extreme operating conditions, and two controllers are applied to control battery temperature with proper intervals which is conducive to enhance the battery charge-discharge efficiency. The results indicate that, for any operating condition, the fuzzy logic controller shows excellence in terms of the tracking accuracy of set-point of battery temperature. Thanks to the establishment of fuzzy set and fuzzy behavioral rules, the battery temperature has been throughout maintained near the set point, and the temperature fluctuation amplitude is highly reduced, with better temperature control accuracy of ∼0.2°C (regular condition) and ∼0.5°C (extreme condition) compared with ∼1.1°C (regular condition) and ∼1.6°C (extreme condition) of optimized on-off controller. While in the case of extreme operating condition, the proposed optimized on-off controller manifests the hysteresis in temperature fluctuation, which is ascribed to the set of dead-band for the feedback temperature. The simulation results cast new light on the utilization and development of model-free temperature controller for the thermal management of lithium-ion battery. [ABSTRACT FROM AUTHOR]

Lithium battery temperatures will increase if the heat produced during the charging and discharging procedures is not promptly vented externally. Fewer investigations have been conducted on materials that can retain good flexibility at room temperature and shape stability at high temperatures under the existing thermal management system for phase change materials (PCM). In this study, a particular kind of flexible composite PCM (CPCM) at room temperature is created to address the issue of heat transfer between the PCM and the power battery. The characteristics of hardness, room-temperature flexibility, form stability at high temperature, and thermal conductivity are compared with those of three other thermally induced flexible CPCMs. The flexibility at room temperature of the new CPCM is demonstrated by the results, which makes assembly easier and helps further lower the contact thermal resistance. Charge–discharge test comparisons of the battery modules employing the chosen CPCM and thermally induced CPCM are performed to further evaluate their thermal management capabilities. The thermally induced CPCM exhibits larger maximum temperature profiles at the discharge rates of 1C, 2C, and 3C than the room-temperature flexible CPCM. The variations in maximum temperatures are 0.96, 1.48, and 2.08 °C. [ABSTRACT FROM AUTHOR]

Performance of battery cells in an electric vehicle (EV) highly depends on environmental temperature. However, many studies do not consider its regional or seasonal characteristics. These characteristics can have a significant impact on the EV battery life in California, where there is a large variation of climate across the state. In some regions, the maximum ambient temperature can cause a rapid life degradation of the battery cells. In this study, we investigated the environmental temperature effects of six major cities in California on the capacity fade of the EV battery cells. A numerical model of an automotive battery pack and cycle-life model of a lithium-ion battery cell were implemented to predict the cell temperature and its corresponding capacity loss. The numerical results demonstrated the regional and seasonal effects of environmental temperature must be considered to prevent rapid life degradation in the automotive battery cells. [ABSTRACT FROM AUTHOR]

Battery thermal management system (BTMS) is essential to the safe operation of electric vehicles. In order to improve the heat dissipation performance of BTMS, the Non-dominated sorting genetic algorithm-2 (NSGA2) combined with neural network is used to optimize the battery pack with multiple objectives. First, the three-dimensional battery pack model is converted into the two-dimensional model to simulate 2000 battery packs, saving much calculation time. Subsequently, five parameters, including the width of the inlet and the outlet, the position of the inlet and the outlet, and the battery spacing, are used as design variables to establish a BP neural network model with a good prediction effect of BTMS. After that, the NSGA2 algorithm is used to optimize the neural network model with multiple objectives. Finally, the final design solution with the lowest maximum temperature in the Pareto solution set is selected and simulated. The results show that the maximum temperature of the optimized battery pack is reduced by 7.5 K, the maximum temperature difference is reduced by 67.4%, and the power consumption is reduced by 26%. [ABSTRACT FROM AUTHOR]

This paper discusses an improved thermal management system to ameliorate the performance of lithium-ion battery storage systems for electric vehicles (EVs) applications. A compact and lightweight cold plate is designed and fabricated to fit 18650-type lithium-ion batteries, using aluminum-finned copper tubes. A dynamic temperature PID (proportional, integral, differential) control algorithm for electronic expansion valves is developed to study using EV air conditioning refrigerant, R134a, to control battery modules' temperature with this compact and lightweight thermal management system. The experimental results show that the proposed battery thermal management system can effectively control the battery module's temperature. In addition, during 1C discharge, when the PID temperature algorithm control scheme is used, the maximum temperature difference across the battery module peaks at less than 4°C, and the maximum temperature within the battery module is less than 36°C. [ABSTRACT FROM AUTHOR]

Highlights: The phase change materials possess conformable configuration to the structure of Li-ion batteries in macro-scale and multidirectional thermal pathways for rapid and uniform heat transfer in micro-scale. Hierarchically structured phase change materials achieve dual-mode thermal management ability for heating and cooling Li-ion batteries. Excellent practical battery thermal management performance was verified by 18,650 Li-ion batteries in both cold and hot environments. Phase change materials (PCMs) are expected to achieve dual-mode thermal management for heating and cooling Li-ion batteries (LIBs) according to real-time thermal conditions, guaranteeing the reliable operation of LIBs in both cold and hot environments. Herein, we report a liquid metal (LM) modified polyethylene glycol/LM/boron nitride PCM, capable of dual-mode thermal managing the LIBs through photothermal effect and passive thermal conduction. Its geometrical conformation and thermal pathways fabricated through ice-template strategy are conformable to the LIB's structure and heat-conduction characteristic. Typically, soft and deformable LMs are modified on the boron nitride surface, serving as thermal bridges to reduce the contact thermal resistance among adjacent fillers to realize high thermal conductivity of 8.8 and 7.6 W m−1 K−1 in the vertical and in-plane directions, respectively. In addition, LM with excellent photothermal performance provides the PCM with efficient battery heating capability if employing a controllable lighting system. As a proof-of-concept, this PCM is manifested to heat battery to an appropriate temperature range in a cold environment and lower the working temperature of the LIBs by more than 10 °C at high charging/discharging rate, opening opportunities for LIBs with durable working performance and evitable risk of thermal runaway. [ABSTRACT FROM AUTHOR]

Battery thermal management is very crucial for the safe and long-term operation of electric vehicles or hybrid electric vehicles. In this study, numerical simulation method is adopted to simulate the temperature field of Li-ion battery cell and module. It is proved that the maximum temperature and maximum temperature difference of battery cell and module increase with the increase of charge/discharge rate (C-rate) of the battery. For battery module, it can reach a maximum temperature of 61.1°C at a C-rate of 2 under natural convection condition with the ambient temperature of 20.0°C. A battery thermal management system based on micro heat pipe array (BTMS-MHPA) is deeply investigated. Experiments are conducted to compare the cooling effect on the battery module with different cooling methods, which include natural cooling, only MHPA, MHPA with fan. The maximum temperature of battery module which is cooled by MHPA with a fan is 43.4°C at a C-rate of 2, which is lower than that in the condition of natural cooling. Meanwhile, the maximum temperature difference was also greatly reduced by the application of MHPA cooling. The experimental results confirm that the feasibility and superiority of the BTMS-MHPA for guaranteeing the working temperature range and temperature uniformity of the battery. [ABSTRACT FROM AUTHOR]

Different battery thermal management (BTM) for a 18650 cylindrical Li-ion battery pack were simulated based on the lumped model. Phase change material (PCM) was introduced for its benefits: high latent heat and uniform melting temperature. However, the heat absorbed into the PCM was not dissipated to the environment. Thus, an additional cooling mechanism was required to reach satisfying temperature limits (45 °C for lifespan and 50 °C for safety). These include natural convection cooling, forced convection cooling, finned-natural convection cooling, PCM cooling, and PCM cooling coupled with liquid cooling channels. The temperature of the battery pack using natural convection, finned-natural convection, and PCM cooling reached 62.1 °C, 55 °C, and 50 °C, which were equal or over (50 °C), while it decreased to 49 °C using forced convection, which was over (45 °C). However, PCM coupled with liquid cooling channels satisfied the requirements, and the temperature was reduced to 42 °C using this system. [ABSTRACT FROM AUTHOR]

Cold plate is an important component for a liquid battery thermal management system. In order to study the transient thermal performance of the cold plate under conditions with sharply increasing heat loads, the numerical model of a battery cold plate is established. The validation experiment shows that the error between the simulation and experiment is around 2.5% to 5%. Effects of the coolant flow rate, the increase in heat flux, and the channel number are analyzed to study the transient thermal performance of the cold plate. Results show that the average temperature of the cold plate at 540 s is lowered from 28.3°C to 26.9°C when the coolant flow rate is raised from 0.065 kg/s to 0.165 kg/s. The temperature deviation is decreased when the coolant flow rate is increased from 0.065 kg/s to 0.115 kg/s; however, it is slightly increased if the coolant flow rate is further increased. Both average temperature and temperature deviation are raised if the final heat flux is increased from 11 000 W/m2 to 16 500 W/m2, which are 2 and 3 times of the initial, respectively. In addition, increasing the channel number has slightly positive effect on the average temperature of the cold plate, while the temperature deviation is increased when the channel number is increased from 3 to 11 due to the non-uniform velocity distribution between each channel. The results of this study will be helpful during the design of cold plate for battery thermal management, especially for transient conditions with sudden rising heat loads like thermal runaway. [ABSTRACT FROM AUTHOR]

Battery thermal management system (BTMS) is a key to control battery temperature and promote the development of electric vehicles. In this paper, the heat dissipation model is used to calculate the battery temperature, saving a lot of calculation time compared with the CFD method. Afterward, sensitivity analysis is carried out based on the heat dissipation model, and four structural parameters and inlet airflow rate are selected as design variables. Based on not increasing the volume of the battery pack, BTMS is optimized with the objective of reducing power consumption, maximal temperature difference, and maximal temperature. In terms of multiobjective optimization algorithms, the overall performance of the NSGA-III_DE (Non-dominated Sorting Genetic Algorithm-III_Differential Evolution) algorithm is much better. Therefore, the NSGA-III_DE algorithm is used to perform multiobjective optimization on the heat dissipation model to obtain the optimal design variables. The optimization result shows that compared with the original BTMS, the optimized BTMS has a decrease of 16.7% in power consumption, 60.7% in maximal temperature difference, and 3.4 K in maximal temperature. [ABSTRACT FROM AUTHOR]

Preventing thermal runaway propagation is critical to improve the fire safety of electric vehicles. Experiments are conducted on the designed battery modules to study the effects of aerogel, liquid cooling plate, and their combination on the prevention mechanism of thermal runaway propagation. The characteristics of temperature, voltage, mass loss, and venting during the thermal runaway propagation process are compared and analyzed. The results indicate that: (1) adding the insulation material of aerogel can postpone the thermal runaway propagation, but may not completely cut-off the propagation process; (2) there is no obvious delay of thermal runaway propagation by adding the liquid cooling plate only, the propagation speed may be accelerated instead; (3) the thermal runaway propagation can be prevented by using aerogel and liquid cooling plate together. The study reminds us that safety design of battery thermal management system should consider the comprehensive heat transfer pathways in order to effectively prevent thermal runaway propagation. [ABSTRACT FROM AUTHOR]

The exergy analysis of an electric vehicle heat pump air conditioning system (HPACS) with battery thermal management system was carried out by studying the exergy loss of each component. The results indicate that the compressor is the main source of system exergy loss in all operation conditions. The exergy loss distribution of HPACS is almost the same when the battery thermal management system integrated into the HPACS in cabin and battery mixed cooling mode and the system exergy loss was linearly related to the compressor speed in cooling modes. The performance of the HPACS is better than that of the positive temperature coefficient (PTC) heater in cabin heating mode. The degree of exergy efficiency improvement of the alternative mode was discussed at all operation conditions in cabin heating mode. The results indicate that the optimization effect using the electric vehicle HPACS to replace the PTC heater is obvious at lower compressor speed, surrounding temperature and internal condenser air flow rate. [ABSTRACT FROM AUTHOR]

Heat generation and accumulation during working schemes of the lithium-ion battery (LIB) are the critical safety issues in hybrid electric vehicles or electric vehicles. Appropriate battery thermal management is necessary for ensuring the safety and continuous power supply of rechargeable LIB modules. In this study, thirty cylinder 18650-type cells were fabricated a 6S5P battery module with a 2-mm spacing between cells to evaluate exothermic trajectories. The modules, equipped with a forced-air cooling system, were charged at 1 C-rate and discharged at 1, 1.5, and 2 C-rates for three cycles in each test; thermocouples were connected to the cells to track the variances in temperature and voltage. The efficiency of the developed forced-air cooling system was estimated to be 73.0% in case 1 with the 1 C discharge rate, and the temperature difference (TD) was less than 5.0 °C. The maximum temperature (Tmax) of this case was maintained below 45.0 °C showing uniform heat distribution. Moreover, extreme heat accumulation developed inside the module and damaged the adjacent LIBs during fast 2 C discharge test. Our TD testing showed that a forced-air cooling system in the LIB module provides effective heat dispersion under normal discharge conditions. [ABSTRACT FROM AUTHOR]