Battery Thermal Characteristics Research Articles

Computational investigations of battery thermal management system with environmental effects employing a combination of phase change materials and forced air cooling

ABSTRACT The thermal management system of battery pack was investigated based on the combination of two different phase change materials OM35 and Paraffin wax coupled with forced air cooling to maintain the thermal distribution in the battery pack at a discharge rate of 1C. Numerical investigations were carried out by computational fluid dynamics (CFD) to understand the effects of battery thermal characteristics on environmental conditions in different cities of India. Furthermore, the thermal behavior of the system in an active and passive cooling was analyzed. The result indicates that active cooling can reduce the temperature rise in the battery pack by 2.8°C in the discharge cycle. The above studies identified active cooling not always required when the vehicle speed increases above 40 km/h. Environmental conditions during summer have a significant impact on the temperature rise in the battery pack.

A comparative study of cooling schemes for laminated lithium-ion batteries

The thermal characteristics of batteries in electric vehicles are important for the vehicle performance and safety. In this work, various battery thermal management methods for laminated lithium-ion batteries are evaluated by experiments and numerical simulations. First, a simulation scheme is proposed and verified by the results of the experiments conducted in this study. Then, five thermal management methods, including air natural convection, natural or forced convection with fins sandwiched between battery cells, forced convection with slotted fins, and natural convection with fins and phase change material (PCM) are numerically investigated. The results show that 3- mm thick copper fins greatly improve the cooling effect. At low discharge rates, natural convection with fins meets the cooling requirements. At high discharge rates, forced convection with fins or natural convection with fins and PCM is necessary to meet the cooling requirements. By replacing the copper fins with aluminum fins, the fin thickness should be increased by 1 mm to meet the cooling requirements, while the battery pack total weight is decreased by 41%, indicating that aluminum has potential in battery thermal management systems in electric vehicles.

An Energy Storage System’s Operational Management and Control Method Considering a Battery System

Losses in energy storage systems (ESSs) result from losses in battery systems and power conversion systems (PCSs). Thus, the power difference between the input and output occurs as a loss, which is considered an operational cost. Additionally, since battery systems consist of modules, there is always a temperature difference. Even if voltage balancing is conducted, deviations between the state of health (SoH) and state of charge (SoC) always exist. Therefore, a battery characteristic should be considered in relation to the efficient operation of an ESS. In this paper, charging control is implemented based on the SoC. When errors occur in the beginning, the coulomb counting method (CCM) continues to produce errors; it also calculates the SoC through an improved equation. Thus, it can calculate the SoC by using high-accuracy initial values. Moreover, battery deterioration occurs during charging and discharging, which increases a battery’s internal resistance. This reduces the switching time to the battery cut-off voltage or constant voltage (CV) mode, so it becomes possible to calculate the SoH. Therefore, in this paper, the algorithms and equations are proposed to perform SoH operations according to the charging time that is able to reach CV after charging. A conventional battery is usually charged by using constant current (CC) charging until the voltage of the battery module reaches the cut-off area. A switch to CV then occurs when the cut-off area is reached and maintained. However, SoC-based selective charging control is carried out to prevent heat problems. In addition, the battery is charged safely and efficiently by conducting SoH prediction considering the battery thermal characteristics, which vary depending on the charging time and other characteristics. In this paper, a 3 kW ESS was produced, and the proposed algorithm’s feasibility was verified.

Improved thermal performance of a large laminated lithium-ion power battery by reciprocating air flow

Thermal safety issues are increasingly critical for large-size laminated Lithium-Ion Batteries (LIBs). Despite a number of investigations conducted on the Battery Thermal Management System (BTMS) with reciprocating air-flow cooling, large laminated power LIBs are still not sufficiently investigated, particularly in the view of battery thermal characteristics. The present study investigates the thermal behaviors of an air-cooled NCM-type LIB (LiNi1−x−yCoxMnyO2 as cathode) from an experimental and systematic approach. The temperature distribution was acquired from different Depth of Discharge (DOD) by the infrared imaging (IR) technology. A reciprocating air-flow cooling method was proposed to restrict the temperature fluctuation and homogenize temperature distribution. Results showed that there was a remarkable temperature distribution phenomenon during the discharge process, the temperature distribution was affected by direction of air-flow. Forward air-flow (from current collector side to lower part of battery) was always recommended at the beginning of the discharge due to the thermal characteristics of the battery. After comprehensive consideration on battery temperature limit and cooling effect, the desired initial reversing timing was about 50% DOD at 3 C discharge rate. Different reversing strategies were investigated including isochronous cycles and aperiodic cycles. It was found that the temperature non-uniformity caused by heat accumulation and concentration was mitigated by reciprocating air-flow with optimized reversing strategy.

(Invited) Mesoscale Insights into Electrode Thermal Behavior for Li-Ion Battery Safety

Thermal implications continue to remain a challenge and critical determinant for safe and reliable operation of Li-ion batteries in high-energy/-power applications, such as electric vehicles. Unwanted local temperature excursion, due to self-heating and/or under abuse scenarios, may lead to thermal runaway. Thermo-electrochemical interactions in porous electrodes play a critical role, which dictate thermal localization and extremes during operation. While system-level thermal management targeted for effective heat distribution and dissipation are typical strategies for Li-ion battery safety, the implications of electrode-level thermo-electrochemical interplay are not well understood. In this presentation, mesoscale underpinnings of electrode interface and microstructural attributes will be examined in the context of lithium-ion battery thermal characteristics and safety.

A Temperature-Based Peak Power Capability Estimation Method for Lithium-Ion Batteries

The accurate estimation of the state of power (SoP) in battery systems is crucial for battery safety of hybrid electric vehicles and pure electric vehicles. Discharge or charge with large current might lead to significant rise of temperature to batteries. To improve the estimation accuracy of SoP for battery management systems, thermal characteristics of batteries during acceleration or deceleration of electric vehicles are considered. Considering the heat transfer from electrochemical reactions and joule heating to the air and consequently a corresponding rise of battery temperature, a model is established in Matlab/Simulink® and integrated into the calculation process of SoP based on an 18650-type cylinder lithium-ion battery. The corresponding simulation results show that temperature limits have more influence than state of charge limits and terminal-voltage-based limits under high air temperature and high battery temperature. It is proven that multi-constraint SoP estimation method including the thermal effect has the potential to achieve higher prediction precision compared with the general SoP estimation methods.

Experiment and simulation of a LiFePO4 battery pack with a passive thermal management system using composite phase change material and graphite sheets

A passive thermal management system (TMS) for LiFePO4 battery modules using phase change material (PCM) as the heat dissipation source to control battery temperature rise is developed. Expanded graphite matrix and graphite sheets are applied to compensate low thermal conductivity of PCM and improve temperature uniformity of the batteries. Constant current discharge and mixed charge–discharge duties were applied on battery modules with and without PCM on a battery thermal characteristics test platform. Experimental results show that PCM cooling significantly reduces the battery temperature rise during short-time intense use. It is also found that temperature uniformity across the module deteriorates with the increasing of both discharge time and current rates. The maximum temperature differences at the end of 1C and 2C-rate discharges are both less than 5 °C, indicating a good performance in battery thermal uniformity of the passive TMS. Experiments on warm-keeping performance show that the passive TMS can effectively keep the battery within its optimum operating temperature for a long time during cold weather uses. A three dimensional numerical model of the battery pack with the passive TMS was conducted using ANSYS Fluent. Temperature profiles with respect to discharging time reveal that simulation shows good agreement with experiment at 1C-discharge rate.

Two-dimensional electrochemical–thermal coupled modeling of cylindrical LiFePO4 batteries

The distributions of potential and reaction rates in a lithium ion battery during discharge process have great influences on the battery thermal characteristics. A two-dimensional electrochemical–thermal model has been developed for a cylindrical LiFePO4 battery by coupling the mass, charge, and energy conservations as well as the cell electrochemical kinetics. The model also includes battery current collecting tabs. The modeling results are validated for both the electrochemical performance and thermal behavior during galvanostatic discharge process. The modeling results agree well with the experimental data. The placement of the positive and the negative current collecting tabs on the cylindrical battery was found to have a significant effect on the distributions of its potential and local reaction rates, which therefore affect heat generation rates, and thus the distribution of the temperature within the battery.