Series-parallel Configuration Research Articles

Cost-effective one-time configuration for bridge-linked thermoelectric generator array using INFO optimizer

One of the key mechanisms of enhancing the power output of Thermoelectric Generators (TEG) under nonuniform temperature distribution (NUTD) is to restructure their arrays to disperse the NUTD profiles. Existing research works in this area primarily propose dynamic reconfiguration techniques of TEG arrays as a potential solution to maximize their output powers while taking no notice of the highly associated costs of their implementation, i.e., sensors, switches, and maintenance, in addition to the complexity of operation and limited service lifetime of switches. To alleviate these drawbacks, this paper introduces an optimization model for a one-time configuration (OTC) of TEG arrays to maximize their output powers while accommodating multiple NUTD profiles simultaneously. Using the INFO optimizer, the introduced optimization model yields the OTC layout for both symmetrical and asymmetrical TEG arrays across various NUTD scenarios. Given its superior performance, the optimization model is applied to the bridge-linked (BL) TEG array and compared to other configurations such as series (S), series-parallel (SP), and standard BL. The results of the proposed OTC model are compared with (1) standard, non-optimized SP and BL configurations and (2) different dynamic-based reconfiguration techniques. Further, the performance of the proposed model is tested and validated experimentally in the laboratory for the available symmetrical hardware setup, 5 × 5, TEG array under varying NUTD profiles. Compared to dynamic reconfigurations, the results show that the proposed OTC technique provides a partially optimal and cost-effective solution to enhance the output power of TEG arrays under different NUTD. Specifically, for 9×9 and 10×15 TEG arrays, the OTC saves approximately 1,498.5 ($) and 2750 ($) compared to dynamic reconfigurations, respectively. Moreover, BL-based OTC enhances the TEG array harvested power by maximum values of 1.7532%, 2.43%, and 3.156% compared with the standard S, SP, and BL configurations, respectively, based on the hardware setup. Throughout the detailed comparison between the proposed OTC and dynamic reconfiguration techniques, this paper contributes to a deeper understanding of the trade-offs between these configuration techniques and addresses a critical gap in the current research landscape of enhancing the output powers of TEG arrays.

Sound absorption performance and mechanism of aluminum foam with double-layer structures of conventional and porous cell walls

Open-cell aluminum foam exhibits sound absorption valleys in the 2500-4000 Hz range, reducing its sound absorption performance in the 800–6300 Hz range. This paper prepared a novel aluminum foam with a double-layer structure using the infiltration casting method, and its pore structure, sound absorption performance, acoustic model, and sound absorption mechanism are investigated. The double-layer structure consists of a conventional pore (CP) layer with a single pore size of 250 μm or 600 μm and a porous cell wall (PCW) layer with double pore diameters of 250 μm and 600 μm. As the thickness ratio between the CP and PCW layers decreases, the acoustic absorption valley value of the double-layer structure increases when combined with a small-pore CP layer. In contrast, it decreases slightly when combined with a large-pores CP layer. The double-layer structure reaches a sound absorption valley value and average sound absorption coefficient of 0.912 and 0.902, respectively. The double-layer structure's sound absorption valley value is better than that of a homogeneous structure, improving sound absorption performance. A Lu modified model is established to characterize the sound absorption of the double-layer structure, which closely matches the experimental results. The modified model further analyzed the vital geometrical parameters affecting the absorption valleys. Acoustic impedance analysis shows the enhanced sound absorption valleys are due to: 1) Gradient acoustic impedance reduces sound reflections at the air-structure interfaces and increases secondary reflection at the interfaces in the structure; 2) The series–parallel configuration increased the resonance peak bandwidth, while the dual-sized resonance cavities regulated the resonance peak frequency.

An experimental study on thermal runaway propagation over cyclic aging lithium-ion battery modules with different electrical connections

This paper investigates the thermal runaway propagation characteristics of cyclic aging battery modules connected in series, parallel, and series-parallel configurations. Additionally, a comparative analysis of the thermal runaway characteristics among the three battery module configurations is performed. In this experiment, voltage, mass, and other parameters of cells are measured. The temperature response reveals that: when comparing the three battery module configurations, the parallel module has the highest maximum temperature of thermal runaway at 720 °C, followed by the series and series-parallel combined configurations at 683 °C and 669 °C, respectively. The parallel module also exhibits the fastest propagation rate of thermal runaway, which is further intensified by cyclic aging. Regarding the voltage response: the series configuration has five stages of voltage variation during thermal runaway, while the parallel configuration has two stages, and the series-parallel combined configuration has three stages. Cyclic aging accelerates the voltage decline during thermal runaway for all three battery module types. In terms of mass response: the 2P2S configuration experiences the highest mass loss of 55.7 g, followed by the parallel (40.8 g) and series (34.7 g) configurations. Preliminary heat transfer analysis shows that: the average heat transfer during thermal runaway is highest for the 2P2S configuration (20,161 J), followed by the 4S (18,913 J) and 4P (18,773 J) configurations. Cyclic aging reduces the overall heat transfer. Electrical connections have minimal impact on heat transfer within the battery modules. Specifically, in the 4S, 4P, and 2P2S configurations, the heat transfer attributed to electrical connections accounts for only 1.2 %, 0.4 %, and 7.3 % respectively, of the overall heat conduction through the battery shell.

Enabling the transfer matrix method to model serial–parallel compliant mechanisms including curved flexure beams

AbstractCompliant mechanisms with curved flexure hinges/beams have potential advantages of small spaces, low stress levels, and flexible design parameters, which have attracted considerable attention in precision engineering, metamaterials, robotics, and so forth. However, serial–parallel configurations with curved flexure hinges/beams often lead to a complicated parametric design. Here, the transfer matrix method is enabled for analysis of both the kinetostatics and dynamics of general serial–parallel compliant mechanisms without deriving laborious formulas or combining other modeling methods. Consequently, serial–parallel compliant mechanisms with curved flexure hinges/beams can be modeled in a straightforward manner based on a single transfer matrix of Timoshenko straight beams using a step‐by‐step procedure. Theoretical and numerical validations on two customized XY nanopositioners comprised of straight and corrugated flexure units confirm the concise modeling process and high prediction accuracy of the presented approach. In conclusion, the present study provides an enhanced transfer matrix modeling approach to streamline the kinetostatic and dynamic analyses of general serial–parallel compliant mechanisms and beam structures, including curved flexure hinges and irregular‐shaped rigid bodies.

Study of the potential for solar power plant at At Taqwa Mosque Using PV Syst

Countries located on the equator have a relatively high intensity of solar radiation. The thing that is most needed in a solar power plant is the intensity of solar radiation. Based on this, Indonesia is very suitable for implementing solar power plants. The power produced by a solar power plant is directly pro-portional to the intensity of solar radiation received by the solar panels. To maximize electrical power production, it is necessary to design a series of solar panel units to be connected in series or parallel. Solar panels connected in parallel will increase the nominal total voltage, whereas when connected in series they will increase the nominal total current. This research discusses the effect of the series-parallel configuration of solar panel installation on the power production received in a building in the campus environment. The method used to obtain the most optimal energy production is to use a combination of series and parallel solar panels. Daily sunlight data is simulated via PvSyst. The research results show that the most optimal energy production is obtained by designing a series circuit of 20 panels combined with a parallel circuit of 5 panels. The more modules connected in series, the total voltage will increase. The more modules that are connected in parallel, the total current will increase.

Monitoreo de la confiabilidad del sistema hombre-máquina del área de mecanizado mediante la distribución de Weibull

This publication presents the development of a method that seeks to monitor the parameters β (shape) and η (scale) for each component-subsystem combination following the Weibull distribution, necessary for the calculation of the reliability of the man-machine system in the machining area. This system defines the workshops of the metal-mechanic, with high-mix and low-volume batch production where conventional and Computerized Numerical Control (CNC) machines are involved, which share the manufacturing of parts that sometimes are unique, or their manufacturing period is short. The design of the man-machine system is based on the analysis of the failures of non-conforming parts in the machining area and on the failure rates, which the statistical model is developed for its evaluation, considering the 2-parameter Weibull distribution, and a redundant system with series-parallel configuration. The results obtained were based on the theoretical-practical, using mathematical and statistical models, as well as the Study Case. With the use of mathematical and statistical models, it is demonstrated that the probability of failure (risk) of the man-machine system is time-dependent and is generated by mechanical type stresses, which occur in the manufacture of parts.

Cell to Pack Modelling of Li-Ion Batteries for Electric Vehicle Applications: Development and Potential Challenges

Electric vehicles (EVs) and hybrid electric vehicles (HEVs) which are powered by Li-ion batteries (LIBs) have the potential to address the challenges of reducing the dependence on fossil fuels and environmental pollution caused by the transportation sector. However, for the reliable and safe operation of the EVs and HEVs, an accurate estimation of the state of charge (SOC) and state-of-health (SOH) of the battery pack is required. The battery capacity degrades with cycling and calendar ageing over time and usage of the vehicles, which reduces the power capability and driving range of the vehicle. An accurate prediction of the battery SOC and SOH can assist the vehicle user in planning to reach the next charging station or the destination with enough range left before the battery gets fully discharged, hence avoiding annoying circumstances.Battery models have been widely employed in battery health and SOC prediction and can successfully predict the SOC and SOH of individual cells. However, the translation of these models from cell to pack levels adds several unknown critical factors which affect the model prediction capability significantly.Our proposed ECM model is based on the electrical and thermal behavior of individual cells, and it accounts for critical factors such as cell-to-cell variations, temperature gradients, and aging effects. We also incorporate a series-parallel configuration to simulate the behavior of multiple cells at the module and pack levels. By upscaling the model in this way, we can accurately predict the SOC and SOH of the entire battery pack, and provide reliable estimates of the remaining driving range and charging requirements.We anticipate that our proposed ECM model will significantly improve the accuracy of SOC and SOH predictions, which will enable EV/HEV users to better plan their trips, avoid unexpected battery failures, and improve the safety of EV/HEV batteries. Furthermore, our study has the potential to inform the design of future battery technologies and contribute to the transition toward sustainable transportation powered by clean energy sources.

A H-Bridge-Multiplexing-Based Novel Power Electronic Transformer

Cascaded H-bridge power electronic transformers (CHB-PET) play a pivotal role in distribution grids and their efficient operation. The input series and output parallel (ISOP) configurations result in a huge number of power switching devices, high-frequency transformers (HFT), and capacitors in high-voltage, high-capacity CHB-PET, leading to the need for high hardware costs and huge-sized CHB-PET, which further poses a significant challenge to the engineering feasibility and marketability of the CHB-PET. To address these issues, a CHB-PET topology is proposed in this paper. The novel topology exploits the concept of multi-frequency modulation to achieve power decoupling and power unit multiplexing through reasonable LC resonant frequency selection, which optimizes the ISOP structure and ultimately reduces the hardware cost and size of the CHB-PET. In this study, the effectiveness of reducing the number of power switching devices and HFT is firstly analyzed, and after describing its working principle, the control strategy of each power conversion link of PET is discussed before the correctness and effectiveness of the CHB-PET topology and control strategy proposed in this paper are verified via simulation.

Mathematical modelling and experimental validation of thermal conductivity of outer layer of fire protective clothing

Motivation for development of this mathematical model is the difficulties related to the experimental measurement of the thermal conductivity like frequent sample preparation, experimental setup availability and lack of easier methods for quick estimation of thermal conductivity of outer layer of fire protective clothing. Considering this, various studies were devoted in the past to determine the thermal conductivity of fabrics. Two mathematical approaches for prediction of thermal conductivity of woven outer layer have been presented in the present study. Series-parallel thermal resistance configuration has been used for prediction of effective thermal conductivity of the fabric. First approach uses input values of structural parameters and can be useful in the development of new woven fabrics for outer layer of fire protective clothing. Second approach uses fibre volume fraction and thermal conductivity of fibre and air. It is suitable for predicting thermal conductivity of finished fabrics. The values obtained from mathematical model were validated with experimental values.

Geometrically nonlinear analysis of compliant mechanisms using a dynamic beam constraint model (DBCM)

Compliant mechanisms with intermediate-deformation ranges are increasingly applied in large-stroke precision manipulators and other actuators. The nonlinearities of axially-loaded stiffening and kinematics-arching effects (P-Δ effects) have a pronounced influence on the kinetostatic and dynamic behaviors of such a class of compliant mechanisms. A dynamic beam constraint model (DBCM) with the pseudo-static characteristic is reported for the nonlinear kinetostatics and large-amplitude vibration analyses of intermediate-deformation compliant mechanisms. Firstly, the DBCM of flexure beams is derived in a closed-form equation on the frequency domain, including the P-Δ effects. A matrix-based modeling methodology with a step-by-step iteration procedure is then introduced to calculate the nonlinear performance of general planar compliant mechanisms with serial-parallel configurations avoiding inner force analysis and kinematics calculation. Except for the static constraint behaviors in the BCM, the amplitude-dependent resonance frequency is captured with the DBCM. Theoretical, numerical and experimental comparisons for a double parallel guiding flexure pivot and Scott-Russell compliant amplifying mechanism verify the feasibility of the DBCM. In summary, the DBCM enables both the nonlinear kinetostatics and large-amplitude vibration analyses of moderately large-stroke compliant mechanisms in a straightforward way.

Performance Evaluation of LiBr-H2O and LiCl-H2O Working Pairs in Compression-Assisted Double-Effect Absorption Refrigeration Systems for Utilization of Low-Temperature Heat Sources

To improve the performance of conventional double-effect absorption refrigeration systems (DEARS), new series parallel (SP) and reverse parallel (RP) configurations using LiCl-H2O and LiBr-H2O as working fluids, combined with two vapor compressors (VC), are proposed and thermodynamically evaluated. The effects of the distribution ratio (D) and compression ratio (CR) on the system performance are discussed. The results reveal that both configurations can extend the operation ranges of DEARS effectively at a higher distribution ratio, and the performance for low-grade heat source utilization is improved substantially by the use of VC. The compressor positioned between the evaporator and absorber is superior to that between the high-pressure generator and low-pressure generator because of the better performance improvement and larger operating ranges. In all the examined cases, LiCl-H2O systems perform better than LiBr-H2O systems in terms of the coefficient of performance (COP) and exergetic efficiency. At the higher CR of approximately 2, the compression-assisted DEARS can be driven by heat sources below 100 °C with high levels of COPs above 1.16 for the LiBr-H2O working pair and 1.29 for the LiCl-H2O working pair. The system can operate at the optimum condition by adjusting the CR values according to the characteristics of the heat sources.

Effect of large redundant volume on the performance of multiple turns helium pulsating heat pipe

The quench process in high-field superconducting magnets releases a significant amount of energy, leading to a rapid increase in local temperature. This temperature rise can result in damage to the magnet components and even lead to magnet burnout. Therefore, it is crucial to effectively dissipate heat after a quench event occurs. Helium pulsating heat pipes (PHPs), as a novel and highly efficient heat transfer element, have been investigated for cooling superconducting magnets. However, during a quench event, the internal pressure of the helium PHP increases rapidly due to the sharp temperature rise, which can potentially cause pressure overload and damage to the PHP itself. Additionally, higher filling ratios exacerbate the pressure rise. One potential solution to address this issue is connecting a buffer tank to the PHP to reduce the pressure. However, this approach introduces a larger redundant volume, consequently diminishing the heat transfer performance of the helium PHP. This study focuses on mitigating such degradation through adjustments in structural design and optimization of operating parameters, particularly the filling ratio. By employing three different configurations of the PHP, the study investigates the coupling effect between structure and redundant volume on the performance of the helium PHP. The results indicate that, except for the series–parallel PHP with a filling ratio of 94.2 %, connecting the PHP to a buffer tank weakens the heat transfer performance in other configurations. Analysis of the series–parallel configuration 24-turn helium PHP reveals that the migration of helium gas among sub-PHPs facilitates pulsating motion, thereby alleviating the detrimental effects of the large redundant volume. Overall, this research examines methods to mitigate the heat transfer performance degradation caused by the introduction of a buffer tank and larger redundant volume in helium PHPs. The findings underscore the importance of considering the structural design and operating parameters to optimize the cooling efficiency of superconducting magnets.

ANALYSIS OF GLOBAL AND LOCAL MAXIMUM POWER POINTS IN PV ARRAYS UNDER PARTIAL SHADING CONDITION

Partial shading (PS) has a significant impact on the decrease in efficiency of photovoltaic (PV) array and performance of maximum power point tracking (MPPT) that must be addressed. We conduct an analysis and evaluation of local maximum power point (LMPP) in terms of quantity, and global maximum power point (GMPP) in terms of magnitude and diversity. Simulation is carried out using single diode ideal model and nine generic PS patterns that are specifically designed to bring up the substantial characteristics of the LMPP and GMPP and applied to series-parallel (SP) and total cross-tied (TCT) configurations. The SP configuration has LMPP with two, three, and four peaks, appearing three times each. The TCT configuration has two peaks that appear six times, three peaks that appear once, and four peaks that appear twice. The SP configuration experiences power losses ranging from 56% to 72%, while the TCT configuration has power losses ranging from 52% to 64%. The SP configuration generates a maximum voltage of 76.64 volts and a minimum of 39.20 volts, while the TCT configuration generates a maximum voltage of 77.62 volts and a minimum of 58.21 volts. With a smaller number of LMPP, a larger magnitude of GMPP parameters, and lower diversity, TCT exhibits better characteristics and performance compared to SP.

Evaluation of series-parallel-cross-tied PV array configuration performance with maximum power point tracking techniques under partial shading conditions

Abstract Tracking the maximum power point is a critical issue with solar systems. The power output of the solar panel varies due to variations in irradiance and temperature. Nonuniform irradiation due to partial shading conditions has a direct impact on the characteristics of photovoltaic (PV) systems. To build a diversity of maximum power point tracking algorithms in solar PV systems, this work focuses on perturb and observe, incremental conductance, and fuzzy logic control methodologies. The suggested fuzzy logic control method outperformed the conventional incremental conductance and perturb and observe algorithms with a collection of 49 rules. This paper presents a novel series-parallel-cross-tied PV array configuration with a developed fuzzy methodology. To comment on the performance of a proposed system under various partial shading conditions, a series-parallel PV array configuration has been considered. The simulation result demonstrates that the fuzzy method has a percentage improvement in the global maximum power point tracking efficiency of 24.85% when compared to the perturb and observe method and a 65.5% improvement when compared to the incremental conductance method under long wide partial shading conditions. In the case of the middle partial shading condition, the fuzzy method has a percentage improvement in the global maximum power point tracking efficiency of 12.4% compared to the perturb and observe method and a 60.7% improvement compared to the incremental conductance method.

Experimental study on performance evaluation of passive valved piezoelectric micropumps with series, parallel and hybrid series-parallel configuration

ABSTRACT To overcome the flow deficit in high pumping flow applications, a parametric study is presented involving three Multiple Micropump system (MMS) configurations: Series Multiple Micropump System (SMMS), Parallel Multiple Micropump System (PMMS) and hybrid Series-Parallel Multiple Micropump System (SPMMS). The performance of the MMS configurations was investigated using analytical and experimental approach. The MMS operating at ‘in-phase’ mode (0° phase difference) was observed to exhibit flow pulsations. Therefore, the MMS was operated at ‘out-of-phase’ mode (90° phase difference) to minimise the flow pulsations. The maximum flow rate at the ‘in-phase’ mode was observed to be 37.58 ml/min, 112.32 ml/min and 51.81 ml/min for SMMS, PMMS and SPMMS configurations respectively. Whereas the flow pulsation results indicate that the degree of flow pulsation for SMMS, PMMS and SPMMS configurations was decreased by 13.4%, 13.5% and 13.3% respectively when operated at ‘out-of-phase’ mode. The maximum back pressure of 140 kPa, 40 kPa and 100 kPa was recorded for SMMS, PMMS and SPMMS configurations respectively. It was found that the flow rate and backpressure vary significantly with the actuation frequency and series-parallel modes for MMS. The proposed series-parallel MMS configurations can be used in biomedical, thermal management and fuel cell applications.

An enhanced reconfiguration approach for mitigating the shading effect on photovoltaic array using honey badger algorithm

The series–parallel configuration is one of the widely utilized schemes in the photovoltaic arrays. The existence of shaded or failed modules in the string of the array has a significant impact on the array-produced power. Therefore, this work introduce an innovative objective function and a novel approach of honey badger algorithm (HBA) as a first time to dynamically reconfigure the series–parallel interconnected photovoltaic array under the partial shading and random failure situations to boost the harvested array’s power. The reconfiguration process is performed via electrically reconnecting the modules among the strings via a set of switches. The performance of the proposed approach is examined with two series of analyses. The first one focuses on handling the impact of partial shading phenomena while the second concerns optimizing the array output in case of existing random failed modules inside the array besides partial shading conditions. Two arrays are considered, including a symmetric 9 × 9 array and an asymmetric 10 × 8 photovoltaic one. The proposed optimizer is compared with a set of recently proposed meta-heuristic approaches, including wild horse optimizer, artificial gorilla Troops optimizer, and particle swarm optimizer to clarify the reason for selecting the HBA optimizer. The harvested global maximum power, the mismatch power loss, and enhancement are quality measures performed to affirm the proposed approach’s ability to enhance the array output power. Moreover, energy-saving and income payback are investigated over a day and a year for two systems using symmetric 9 × 9 array and asymmetric 10 × 8 array. The comparisons and analyses showed that, the reconfigured arrays based on HBA provide higher values of maximum global power with smoother photovoltaic characteristics. Moreover, the 9 × 9 and 10 × 8 PV systems-based HBA save income by the percentage of 18.12%, 24.24% compared with series–parallel systems without reconfiguration per year, respectively.

Graphic Transfer Matrix Method for Kinetostatic and Dynamic Analyses of Compliant Mechanisms

Abstract Kinetostatic and dynamic analyses of compliant mechanisms with complex configurations continue to be an attractive issue for obtaining a process-concise and result-accurate solution. In this paper, the transfer matrix method (TMM) is improved for a unified linear kinetostatics and dynamic modeling of compliant mechanisms with complex serial-parallel configurations in an oriented graphic way. In detail, the transfer matrices of typical building blocks commonly used in compliant mechanisms are summarized and derived. Then, a graphic transfer matrix modeling procedure capturing both the kinetostatics and dynamics of general compliant mechanisms is introduced. The displacement amplification ratio, input/output stiffness, parasitic error, natural frequencies, and frequency response of a typical compliant microgripper and a planar parallel three-degrees-of-freedom (3DOF) nanopositioner are calculated with such a graphic transfer matrix method. The advantages of the proposed modeling method lie in its convenience and uniformity in formulating both the kinetostatic and dynamic behaviors of a class of compliant mechanisms with distributed and lumped compliances in a transfer matrix manner, which has minimal DOF and is easily programmed.

An analysis on comprehensive influences of thermoelectric power generation based on waste heat recovery

The thermoelectric characteristics of the thermoelectric power generation based on waste heat recovery, including the influence factors of cooling water flow rate, the overlapping value between load resistance and internal resistance and pressing block weight, were experimentally discussed. In addition to the experimental analyses of simple series-parallel configuration, the thermoelectric characteristics of complex series-parallel configurations were numerically simulated. The fast locating method was proposed to achieve the optimal thermoelectric characteristic. The results showed that the cooling water flow rate makes slight impact on total pressing block weight. All the thermoelectric characteristics increase with increasing pressing block weight. The overlapping value between internal resistance and load resistance is an core index, which determines the optimum thermoelectric efficiency. The changing law of thermoelectric characteristics of numerical simulations are identical with testing data, but the smoothness of simulation curves are better. Three complex series-parallel configurations perform identical total output power characteristic, which increases with increasing thermoelectric modules. However, the output power of a single thermoelectric module exhibits unique characteristic. The inflection points and peak value points in DSIP, ISDP and ISIP configurations are used to examine the output power characteristics of thermoelectric power generation and a single thermoelectric module.

Novel cell balancing applied near-field coupling and Serial–Parallel Circuit configuration

This paper proposes a near-field cell balancing method to be applied to batteries of higher capacity and power. This method involves a wireless power transfer to balance battery cells, which produces higher efficiency than conventional passive approaches, and faster equalization than active approaches. Cell balancing is a crucial function of the battery management system (BMS) that maintains the balance of charge and discharge between cells of individual batteries. Furthermore, this method is designed to meet the increasing demand for faster cell balancing associated with high-capacity and high-power batteries. We selected a serial–parallel configuration to minimize the technical concern for isolation, or energy transfer to unselected cells. Experiments were conducted with two battery cells, and voltage equalization accelerated by 51% when the proposed cell balancing approach was applied.

Impact of Individual Cell Parameter Difference on the Performance of Series-Parallel Battery Packs.

Lithium-ion power batteries are used in groups of series-parallel configurations. There are Ohmic resistance discrepancies, capacity disparities, and polarization differences between individual cells during discharge, preventing a single cell from reaching the lower limit of the terminal voltage simultaneously, resulting in low capacity and energy utilization. The effect of the parameter difference (difference in parameters) of individual cells on the performance of the series-parallel battery pack is simulated and analyzed by grouping cells with different parameters. The findings reveal that when cells are connected in series, the capacity difference is a significant factor impacting the battery pack's energy index, and the capacity difference and Ohmic resistance difference are significant variables affecting the battery pack's power index. When cells are connected in parallel, the difference in Ohmic internal resistance between them causes branch current imbalance, low energy utilization in some individual cells, and a sharp expansion of unbalanced current at the end of discharge, which is prone to overdischarge and shortens battery life. Interestingly, we found that when there is an aging cell in a series-parallel battery pack, the terminal voltage of the single battery module containing the aging single cell will decrease sharply at the end of discharge. Evaluating the change rate of battery module terminal voltage at the end of discharge can be used as a method to evaluate the aging degree of the battery module. The research results provide a reference for connecting batteries to battery packs, particularly the screening of retired power battery packs and the way to reconnect into battery packs.