Float Charge Research Articles

Smart home power management algorithm using real-time model predictive control for a stand-alone PV system with battery energy storage

A smart home power management system is critical for stand-alone home-photovoltaic (HPV) with battery energy storage. Existing approaches often focus on maximizing power extraction from PV systems without considering real-time power adjustments or battery state of charge (SoC), which can lead to over-current or over-voltage issues that damage the battery. To address these limitations, this paper proposes a home power management algorithm that dynamically adjusts the power flow between the PV system, home loads, and the battery based on real-time system power measurements and battery SoC. This dynamic adjustment ensures an uninterrupted power supply to the home loads while maintaining battery safety. The proposed home manager algorithm features multiple operating modes: Maximum power point (MPP) charging, partial charging, fast charging, float charging, and partial discharging. Each mode is integrated with its dedicated model predictive controller (MPC) to achieve its specific control objective. Finally, through a semi-experimental simulation using a process-in-the-loop (PIL) test approach with the embedded board eZdsp TMS320F28335, testing under various irradiance levels shows that the home manager achieves significant improvement over conventional approaches. For instance, over the MPP mode it achieve a power efficiency of 99.36% with a 2.05% SoC increase, while fast charging mode resulted in 87.44% efficiency with an 11.2% SoC increase. However, float charging mode maintained an 87.27% efficiency with a 2.6% SoC increase, and partial discharging led to a 1.3% SoC decrease. The overall battery efficiency reached 96.45%, demonstrating the algorithm’s ability to optimize power flow, ensure a reliable energy supply, and maintain battery safety under varying weather conditions.

A quantitative internal-short-circuit diagnosis method of lithium-ion batteries for float charging systems

The diagnosis of internal short circuit (ISC) faults in lithium-ion batteries (LIBs) plays an important role in improving battery safety and reducing the occurrence of fire and explosion accidents. Traditional ISC diagnosis methods mainly focus on dynamic operating conditions, and rarely consider stable float charging scenarios with high risks. This paper proposes a quantitative diagnosis strategy for ISC faults in LIBs under different float charging conditions. First, a simulation model of ISC faults for single cells and battery modules under float charging conditions is established. Then, for the LIB packs without a balancing system, three quantitative diagnosis methods (namely Map-based, constant-voltage-source based, and intermittent-charging based) for the ISC faults applicable to different simple and complex float charging systems are proposed. Finally, the method is verified through simulation and experiments, and the results show that an ISC of 0–500 Ω can be detected in various scenarios, and the proposed methods are low-cost, high-precision, and easy to implement for early ISC diagnosis of float charging systems for energy storage.

Combination of float charging and occasional discharging to cause serious LIB degradation analyzed by operando neutron diffraction

Negative synergistic effect of a combination of float charging and occasional discharging.

Maximum Power Point Tracking Charge Controller Using Modified Perturb and Observe Algorithm for Lead Acid Battery

A study was undertaken on development of a modified perturb and observe algorithm for maximum power point tracking (MPPT) charge controller. This MPPT algorithm was developed in Matlab/Simulink environment, using three-state charging method for improved battery charging with higher efficiency. A buck topology was utilised as a DC-DC converter for charge controller implementation. The maximum power of the photovoltaic panel was tracked by a modified perturb and observe algorithm. The battery charge controller charged a lead-acid battery using a three- stage charging strategy including the bulk charge, constant voltage (absorption charge), and float charge stage. The performance analysis of Simulink model was carried out by maximum power point tracking performance, battery charging performance, and overall charge controller efficiency performance. The performance results indicated that the maximum power point tracking was capable to track to the maximum power of PV panel at any solar irradiance variation with power tracking efficiency up to 98 per cent. The efficiency of overall charge controller was up to 98.3%, which matched many high-end commercial charge controller product specifications.

Effects of Lithium Over-Stoichiometry in Li1+xCoO2−δ and Li1+xCo0.95Ni0.05O2−δ on High-Voltage Float Durability and Cyclability

Finding a balance between high energy density and long life is a fundamental challenge in the development of lithium-ion batteries. The energy density of lithium-ion batteries can be enhanced by increasing the upper limit charging voltage of the LiCoO2 positive electrode, but fatal deterioration can occur, especially during high-voltage float charging. In this study, we investigate the 4.5 V float charging durability and cyclability on lithium over-stoichiometric Li1+xCoO2−δ and Li1+xCo0.95Ni0.05O2−δ (x = 0–0.14). The leakage current of accompanied by the structural collapse of positive electrode materials under float charging at 4.5 V could be suppressed by increasing the lithium over-doping. On the other hand, increases in the lithium over-doping resulted in a larger float current at the early stage, which was found by a side reaction accompanied cobalt/nickel dissolution directly linked to the deterioration of the positive electrode materials. The 4.5 V cyclability and float durability of Li1+xCoO2−δ and Li1+xCo0.95Ni0.05O2−δ showed a clear positive correlation, thus indicating that a higher 4.5 V float durability leads to higher cyclability. Our systematic evaluation of both positive electrode materials revealed that x ≈ 0.04 in Li1+xCoO2−δ and x ≈ 0.03 in Li1+xCo0.95Ni0.05O2−δ demonstrated high float durability and cyclability.

Design and Implementation of a Digital Control System for Lead Acid Battery Charging

Ensuring a long battery life and satisfactory performance requires accurate charging cycles. There are three phases to the charge cycle - Constant Current Charge, Constant Voltage Charge, and Float Charge. It is usual that lead acid battery users complain about fast degrading performance because most the low cost commercially available lead Acid Battery chargers provides only single-stage charging phase which is that of constant-voltage charging phase. To ensure long service life and good performance, it is of paramount importance that all charging modes are respected. This said it is clear that the battery charger should have a certain degree of controllability over voltage and current quantities through-out the charging process. In this paper, we designed and built a lead acid battery charger to use in conjunction with a synchronous buck converter topology. After implementing and testing the system, we obtained good results in both the quantitative and qualitative analysis of the implemented system tested, a 12 V- 7000mAh battery. With the help of a MCU-based digital control system containing two different control transfer functions - constant current Feedback Control and Constant Voltage Feedback Control monitoring the charging process proved possible without any overshoot. The prototype showed us an efficiency rating of 86.60%, the maximum error level was recorded at 0.05V, and there were no problems related to overshoot or transient response when testing our prototype which worked flawlessly.

Molecular crowding bi-salt electrolyte for aqueous zinc hybrid batteries

Aqueous zinc metal batteries (AZMBs) represent a promising option for a low-cost, safe and sustainable energy storage system for large-scale applications. However, substandard Zn metal anode performance (hydrogen evolution, dendrites) and cathode instabilities, attributed to water activity and/or water-induced side reactions, still plague their practical deployment. Herein, we investigate the performance of an aqueous Zn//LFP hybrid battery by using molecular crowding electrolytes (MCE) combining a low concentrated bi-salt (Zn(TFSI) 2 and LiTFSI) electrolyte with a crowding agent, namely polyethylene glycol (PEG400). The composition of MCE electrolyte was optimized as a function of the PEG content and the molality of LiTFSI salt. The PEG confines water molecules, thereby reducing the fraction of “free water” molecules as evidenced by combined LSV, Raman, DSC and molecular dynamics simulations studies. Consequently, the reversibility of Zn plating/stripping anode reaction and the long-term cyclability of the Zn//LFP hybrid battery was significantly improved in MCE compared to the conventional electrolyte. Specifically, in our optimized MCE containing 1m Zn(TFSI) 2 and 4m LiTFSI in 70% wt. PEG, the Zn//LFP not only delivers high rate performance but also sustains high capacities (120 mAh g −1 ) with superior long-term cycling stability retaining 65% of its initial capacity over an extended period of 882 h (vs 5% after 205 h) over 200 cycles at 0.2 C compared to the conventional electrolyte. Furthermore, Zn//LFP demonstrates a much lower self-discharge rate (only 5% per month vs 100% in the conventional electrolyte) and superior float charge behavior inferring that the detrimental parasitic reactions in the aqueous Zn-hybrid battery are potentially suppressed in our MCE. These combined results show that this MCE strategy can be used to design high reversible, safe and long-cycling AZMBs for practical applications.

Effects of electrode mass loading on the self-discharge of supercapacitors

Electrode mass loading is an important device parameter for supercapacitors and its effect on electrochemical properties such as energy density, rate performance, and cycle stability has been widely reported. However, how the self-discharge of supercapacitors varies under different mass loadings has not been examined systematically. In this study, we prepared porous activated carbon (AC) electrodes with a series of mass loadings and investigated their self-discharge behavior. It is found that with the increase in mass loadings, the decay rates of open circuit voltages (OCVs) are reduced substantially. Specifically, when the electrode mass loading increased from 0.6 to 10.6 mg cm−2, the cell OCV decay rate at a charging voltage of 1.6 V dropped from 1.07 to 0.05 mV mF−1 hr−1, indicating much slower self-discharge rates at higher mass loadings. Analysis of the self-discharge mechanism suggests that faradaic reactions are the major self-discharge processes for the supercapacitors after float charging. While the OCV decays due to both activation-controlled and diffusion-controlled faradaic reactions are reduced at high mass loadings, the self-discharge attributing to diffusion-controlled faradaic reactions is more affected due to the deeper pores and longer diffusion paths for electrolyte and reactive species in thicker electrodes.

Study on Performance of Ramjet Intake by Changing the Cowl Angle

Most gas turbine engines require the Mach range on the engine face to be at a mild subsonic pace (around Mach 04). Therefore, for a supersonic plane with a gas turbine engine, the characteristic of the air inlet is to slow the supersonic unfastened flow to a subsonic pace and offer a matched air mass float charge to the engine. The gas turbine engine calls for the delivery of uniform excessive general stress restoration air for proper overall performance and operation because the quality of the airflow on the engine face substantially influences the overall performance of the engine, in particular, the total stress loss, which influences the engine thrust and therefore the gasoline consumption. A 2-D supersonic intake is designed for Mach No. 2.4 at an altitude of 11,000 m. The design of the mixed compression supersonic intake is done numerically, and the design with the k- turbulent module is done using CFD. Optimization of the intake is done by changing the cowl deflection in order to get maximum total pressure recovery. Results are compared to knowing the optimal design. The main advantage of mixed compression is that it gives the maximum total pressure recovery at any Mach number. The computation is done with the ANSYS software.

Potassium Polyacrylate-Based Gel Polymer Electrolyte for Practical Zn-Ni Batteries.

Because of their high theoretical value of volumetric energy density, excellent rate performance, and high level of safety, zinc-nickel batteries (ZNBs) show potential applications for uninterrupted power supply (UPS) systems. However, despite all the advantages of ZNBs, the commercial application of ZNBs has been prevented by their short lifetime caused by the shape change, the corrosion, and the dendrite formation of the Zn anode. In this work, we proposed a flexible and durable potassium polyacrylate (PAAK)-KOH gel polymer electrolyte (GPE) prepared in a very simple way to solve the above problems of the Zn anode. The obtained highly porous gel electrolyte showed higher water retention, satisfying ionic conductivity (0.918 S cm-1), and a broad electrochemical stable voltage window. By providing a stable and homogeneous electrode/electrolyte interface for the Zn anode, the gel electrolyte can inhibit the uneven deposition and dendrite formation. As a result, the gel electrolyte greatly prolonged the cycling life to 776 h. In addition, because of the considerably batter corrosion resistance of the Zn anode in the PAAK-KOH GPE, the ZNB with gel electrolyte also exhibited a superior shelf life of more than 431 h and a superior cycling performance under float charge for more than 400 h at 60 °C. This work demonstrates that the gel electrolyte with a simple preparation method is suitable for large-scale practical production and can be successfully used in Zn-Ni batteries as an electrolyte exhibiting excellent performance.

Charge-Controller Optimization on Lead-Acid Battery in Solar PV Systems: Temperature Effects and Efficiency Improvement

Long-term cell performance is very sensitive to the cell operating temperature, and cell storage capacity can degrade quickly, if the temperature is not maintained within a narrow range (25–50 °C) during charging and discharging of (solar) batteries [1]. Efforts are recently being dedicated to developing models that seek to provide insights into that issue. However, not all models consider the operation of the photovoltaic (PV) battery storage system with regard to battery optimization and temperature effects. The present work provides a controllable algorithm to help charge controllers provide exact amount of PV electricity (charge equalization) to batteries with temperature compensation included, and a proposed charging and discharging schedules of the battery storage. The temperature compensated duty cycle for charging is modelled and the pulse-width modulation (PWM) signal is programmed to change with temperature following this duty cycle model. This research work is based on the optimization of solar battery storage where the micro controller-based charge controller enhances battery life by monitoring the temperature and controlling charging voltages and float charging voltages for specific temperatures. A buck converter was simulated in Proteus, and then realized in the laboratory. The duty cycle of the buck converter was adjusted with temperature. Results collected from lab experiments were plotted on MatLab and it shows homogeneity with calculated results. Moreover, battery-charging currents, battery direct current (DC) disconnect and battery switching for charging and discharging were performed for the converter. Future work is to extend this study to large-scale solar photovoltaic systems in order to overcome the operation limits encountered.

Modeling and experimental analysis of battery charge controllers for comparing three off-grid photovoltaic power plants

The study of battery charge algorithm as a sole power storage agent in off-grid systems is essential. The battery charge algorithm has various methods, and the battery in these methods relies on the quantity of charges. Hence, a charge controller is used to safeguard and regulate battery charge and discharge for off-grid photovoltaic (PV) systems. This study presents the 11.4 kWp power plant analysis comprising three 3.8 kWp each of off-grid, hybrid and grid-assisted systems with battery capacities of 900 Ah, 1235 Ah and 910 Ah, respectively, where all the systems were reconfigured to function as off-grids. The battery charge controller charges the lead-acid battery using a three-stage charging strategy, including constant current, constant voltage and float charge stage. A DT80 data logger was installed to simultaneously record the electrical parameters of the systems, while Kipp & Zonen CMP 11 pyranometer was selected to measure solar radiation data. Experimentation with three electric bar heaters, each with fan and humidifier, were used as loads to draw constant power of 1.2 kW from batteries of each system on charging and discharging on an overcast and clear sky days for a week. The useful study is performed in the following ways, MPPT tracking performance, battery charging and discharging performance and charge controller efficiency. The performance results reveal that the MPPT can track the PV module maximum point at solar irradiance from 07h15 to around 12h00 maximum power tracking efficiency. An irradiance of illumination fluctuates from 5 W/m2 to 850 W/m2 while the electrical energy consumed by the loads in off-grid, hybrid and grid-assisted systems are 456.12, 568.87 and 80.00 Wh, respectively. It is estimated that individual owners could charge electric appliances from residential and commercial buildings of solar arrays of clean, renewable solar energy.

Vector analysis of inverse objective function for electrochemical impedance spectroscopy of big capacity lead-acid battery

The important emergency power supply needs a large capacity battery. The batteries are long-term float charging. Electrochemical impedance spectroscopy (EIS) is important for remaining useful capacity warnings. This paper establishes the EIS inverse calculation technique that is centered in the vector objective function and linear interpolation search algorithm. This technique simplifies the initial value preparation and the gradient descent direction search for the inverse calculation of EIS. The root-mean-square errors of online embedded programming are smaller than the offline results of numerical software for EIS. The vector objective function targets the rotation angle of the initial polarization impedance vector to be zero during the EIS inverse calculation. This equivalently replaces the regular minimization of root-mean-square error. The linear interpolation algorithm simplifies the gradient descent direction search to a one-dimensional search for the double-layer capacitance of the initial polarization impedance. This algorithm replaces the conventional graphic method and evolutionary algorithm. The proposed algorithm is verified by the microcontroller at Valve-regulated lead-acid (VRLA) batteries (4200 Ah). The result of the algorithm is close to special numerical software for EIS. This algorithm improves the performance of an embedded management board.

Overview of research on float charging for lithium-ion batteries

Overview of research on float charging for lithium-ion batteries

Highly efficient dendrite suppressor and corrosion inhibitor based on gelatin/Mn2+ Co-additives for aqueous rechargeable zinc-manganese dioxide battery

Metallic Zn anode in aqueous rechargeable batteries generally suffers from corrosion and dendrite formation. In this work, these issues can be tackled by using synergistic effect of Mn2+ ions and gelatin as additives. The dendrite suppression was characterized by scanning electron microscopy and chronoamperometry examinations. It was found that the 0.2 M Mn2+ and 0.5 wt% gelatin in the electrolyte are beneficial to mitigate both dendrite growth and corrosion. Ex situ X-ray diffraction results suggested that the presence of Mn2+ ions during zinc depositing process changes the preferred zinc orientation from the (112) plane to (103) and (002) planes, which are not prone to zinc dendrite growth. The Zn//Zn symmetric cells revealed that the coexistence of Mn2+ ions and gelatin greatly increase the sand’s time (>500 h) of zinc dendrite formation. The assembled Zn//polyaniline/MnO2 battery using Mn2+/gelatin co-added electrolyte demonstrated good capacity retention of 80% after 1000 repeated cycles at 500 mAg−1. Furthermore, float charge current also obviously decreased from approximately 11.8 to 4.3 ~ 7.6 μA under 1.9 V constant voltage.

Improvement of float charge durability for LiCoO2 electrodes under high voltage and storage temperature by suppressing O1-Phase transition

To produce electronic devices with high functionality and longer operating times, the energy density of lithium-ion batteries (LIBs) has to be increased while maintaining a long battery life and high reliability. The energy density of LIBs can be increased by increasing the charge cut-off voltage. The float charge durability of LIBs containing LiCoO2 under high voltage is one of the most important issues in practical use. The leakage current during float charge conditions is caused by the O1 phase transition of LiCoO2. In this study, metal-substituted lithium cobalt oxides, LiCo1-xMxO2 (M = Co, Ni, Al, Mg, and Zr), were investigated to suppress degradation during float charge conditions. When Ni was substituted for Co at an amount of 5%, the float charge durability improved more than 4 times compared to bare-LiCoO2 without lowering the energy density. According to the structural analysis, we proposed the mechanism for improving float charge durability by LiCo1-xNixO2; Ni ions partially migrate to the lithium layer and then stabilize the O3 structure. This Ni ions substitution in LiCoO2 greatly contributes to extending life and the safety of high energy density LIBs containing layered positive materials.

Modeling of Photovoltaic MPPT Lead Acid Battery Charge Controller for Standalone System Applications

This paper presents the circuitry modeling of the solar photovoltaic MPPT lead-acid battery charge controller for the standalone system in MATLAB/Simulink environment. A buck topology is utilized as a DC-DC converter for the charge controller implementation. The maximum power of the photovoltaic panel is tracked by the Perturb and Observe MPPT algorithm. The battery charge controller charges the lead-acid battery using a three-stage charging strategy. The three charging stages include the MPPT bulk charge, constant voltage absorption charge, and float charge stage. The performance analysis of the model is carried out in the following aspects, there are MPPT tracking performance, battery charging performance and overall charge controller efficiency performance are benchmarked with commercial MPPT charge controller for validation. The performance result shows that the MPPT is capable to track to the PV panel maximum point at any solar irradiance variation within 0.5 seconds with maximum power tracking efficiency up to 99.9 %. The three-stage charging strategy also successfully demonstrated. The overall charge controller average efficiency achieved up to 98.3 % which matches many high end commercial solar PV MPPT charge controller product specifications. This validated model contributes to a better sizing of PV panel and battery energy storage for the small and medium standalone PV system.

Electrochemical Performance of Hybrid Cationic Aqueous-Based Rechargeable Battery with Different Current Collectors and Electrolytes

Different zinc foils as anode current collectors by electrowinning in various electrolytes with additives were prepared, which were evaluated through X-ray diffraction (XRD), scanning electron microscopy (SEM), float charge, and Tafel curve tests. The effect of different cathode current collectors, electrolytes, and the as-prepared zinc foils as the anode on the coulombic efficiency and the cycling performance of aqueous batteries were investigated. The results indicate that the initial coulombic efficiency and discharge capacity of the battery with 1 mol/L ZnSO4 and 2 mol/L Li2SO4 are 94.31% and 105.7 mAh/g using graphite as the current collector, which are much higher than 68.20% and 71.0 mAh/g using conductive polyethylene, respectively, attributed to the smaller polarization and electrochemical transfer impedance (Rct) of the former. However, the capacity retention of the latter is much higher than that of the former, especially using the high-concentration-lithium-based hybrid electrolyte, of which it is up to 74.63% even after 500 cycles. Moreover, the cycling performance of a battery with as-prepared zinc foil adding thiourea and gelatin into electrolyte during electrowinning is much better than that without additives, which is due to the smaller corrosion rate and side reaction.

Electrolyte engineering for a highly stable, rechargeable hybrid aqueous battery

Abstract The zinc electrode in secondary zinc batteries suffers from many side reactions, namely corrosion, hydrogen evolution, passivation, and dendrite formation. This electrode also suffers from changes in surface textures, mechanical properties, and volume increases due to the formation and growth of porous space inside the zinc electrode. Keeping the zinc electrode from deterioration is a major challenge because one must address multiple problems at a time. In this study, we introduce a three-functional electrolyte based on ethylene glycol oligomers and aqueous components. When in contact with this electrolyte, the corrosion current density decreases by 37%, which means that corrosion and hydrogen evolution are partially mitigated. The chronoamperometry current density decreases by 77.5%, complemented by a nearly flat and layered zinc deposit (confirmed by SEM and ex situ XRD). Applying this concept to a typical Zn/LiMn2O4 battery with 2 M Li2SO4 and 1 M ZnSO4 mixed electrolyte, the capacity retention is up to 80.2% after 1000 charge-discharge cycles at 4 C rate. This is approximately 12% higher than that of the reference battery using an aqueous electrolyte. Furthermore, the float charge current under constant voltage (2.1 V) dramatically decreases by approximately 36% versus the float charge current of the reference battery, and the rate capability is nearly maintained.

Degradation mechanism of LiCoO2 under float charge conditions and high temperatures

Lithium-ion batteries (LIBs) consisting of LiCoO2 and graphite electrodes exhibit a trade-off relationship between their reversible capacity and cycle/calendar life in terms of the charge cut-off voltage. That is to say, a higher charge cut-off voltage leads to a larger reversible capacity and shorter cycle life. In order to develop LIBs that satisfy both performance criteria (i.e., have a high reversible capacity as well as a long cycling life), the degradation mechanism of the LiCoO2 electrode under float charge conditions and high temperatures is investigated while focusing on the relationship between the structural deterioration of the electrode and capacity fading. Durability tests performed on graphite/LiCoO2 cells under float charge conditions (4.4 V at 60 °C) induced a drop in the open-circuit voltage as well as capacity fading in the LiCoO2 electrode along with the dissolution of a large number of cobalt ions. Acoustic emission histometry, X-ray diffraction, and transmission electron microscopy analyses of the LiCoO2 electrode after the float charge tests revealed that the degradation of the LiCoO2 electrode during the float charge tests occurred as per the following steps: (1) the HF generated by the decomposition of LiPF6 reacts with the charged LiCoO2 electrode, (2) the charged LiCoO2 electrode is disproportionated into CoO2 and Co2+ ions, and finally (3) the CoO2 having an O1 structure decomposes into cobalt oxides containing cobalt ions in a lower oxidation state, which is associated with the evolution of oxygen gas.