Valve Regulated Lead Acid Research Articles

Modeling of the cranking and charging processes of conventional valve regulated lead acid (VRLA) batteries in micro-hybrid applications

The cranking and charging processes of a VRLA battery during stop–start cycling in micro-hybrid applications were simulated by one dimensional mathematical modeling, to study the formation and distribution of lead sulfate across the cell and analyze the resulting effect on battery aging. The battery focused on in this study represents a conventional VRLA battery without any carbon additives in the electrodes or carbon-based electrodes. The modeling results were validated against experimental data and used to analyze the “sulfation” of negative electrodes – the common failure mode of lead acid batteries under high-rate partial state of charge (HRPSoC) cycling. The analyses were based on two aging mechanisms proposed in previous studies and the predictions showed consistency with the previous teardown observations that the sulfate formed at the negative interface is more difficult to be converted back than anywhere else in the electrodes. The impact of cranking pulses during stop–start cycling on current density and the corresponding sulfate layer production was estimated. The effects of some critical design parameters on sulfate formation, distribution and aging over cycling were investigated, which provided guidelines for developing models and designing of VRLA batteries in micro-hybrid applications.

Study of electrochemically active carbon, Ga2O3 and Bi2O3 as negative additives for valve-regulated lead-acid batteries working under high-rate, partial-state-of-charge conditions

Electrochemically active carbon (EAC), Gallium (III) oxide (Ga2O3) and Bismuth (III) oxide (Bi2O3) are used as the negative additives of valve-regulated lead-acid (VRLA) batteries to prolong the cycle life of VRLA batteries under high-rate partial-state-of-charge (HRPSoC) conditions, and their effects on the cycle life of VRLA batteries are investigated. It is found that the addition of EAC in negative active material can restrain the sulfation of the negative plates and prolong the cycle performance of VRLA batteries under HRPSoC conditions. It is also observed that the addition of Ga2O3 or Bi2O3 in EAC can effectively increase the overpotential of hydrogen evolution on EAC electrodes, and decrease the evolution rate of hydrogen. An appropriate addition amount of Ga2O3 or Bi2O3 in the negative plates of VRLA batteries can decrease the cut-off charging voltage, increase the cut-off discharging voltage, and prolong the cycle life of VRLA batteries under HRPSoC conditions. The battery added with 0.5% EAC and 0.01% Ga2O3 in negative active material shows a lowest cut-off charging voltage and a highest cut-off discharging voltage under HRPSoC conditions, and its' cycle life reaches about 8100 cycles which is at least three times longer than that without Ga2O3.

The Failure Analysis and Countermeasures of Starter Battery

The main failure modes of starter battery are discussed, the causes resulting in the premature failure of starter VRLA(valve-regulated lead-acid) battery are analyzed and corresponding countermeasures against failure of starter battery are presented. It proves to be of practical help.

Research on the Activation System of Lead-Acid Battery

For the valve-regulated lead-acid (VRLA) battery, an on-line activation system is designed, which is composed of personal computer (PC), sixteen bits MCU, touch-screen, mass FLASH memory, ferroelectric random access memory (FRAM), Ethernet interface, USB interface, charging module, discharging module, and so on. The charging module is designed based on distributed power supply with low voltage and large current, and using the method of intelligent segmentation-limit-current to realize nondestructive charging. The discharging module is designed with technologies of PID and PWM, and battery discharging with constant current can be realized by controlling the power switches. Test results present that the system runs stably, can activate and repair the battery well in the early days of losing efficacy.

Model-Based State-of-Charge Estimation for a Valve-Regulated Lead-Acid Battery Using Linear Matrix Inequalities

State-of-charge (SOC) estimation for valve-regulated lead-acid (VRLA) batteries is complicated by the switched linear nature of the underlying dynamics. A first principles nonlinear model is simplified to provide two switched linear models and linearized to produce charge, discharge, and averaged models. Luenberger and switched SOC estimators are developed based on these models and propagated using experimental data. A design methodology based on linear matrix inequalities (LMIs) is used in the switched SOC estimator design to obtain a switched Luenberger observer with guaranteed exponential stability. The results show that estimation errors are halved by including switching in the observer design.

A Novel High-Power – Long Cycle Life Energy Storage System for Large-Scale Applications

A novel system and method for removing heat from batteries, capacitors and other energy storage devices during high rate or multi-cycle operation has been proposed in this work. By modifying the exposed posts and inter-cell connecting bus-bars, heat transfer will be increased thus reducing the operating temperature of the battery. Because valve-regulated lead-acid (VRLA) batteries generate higher levels of internal heat, and because they have a lower thermal mass and lower heat transfer properties, these modifications are particularly valuable for these types of batteries. This thermal management technology can be used to improve the operating life of large batteries such as VRLA stationary batteries used for UPS and standby power applications. In very high-power energy storage applications such as load-leveling, peak-shaving or spinning reserve, battery life may be increased to as much as two times by reducing the operating temperature ten degrees centigrade using these proposed concepts.

Low-Voltage-Stress AC-Linked Charge Equalizing System for Series-Connected VRLA Battery Strings

This paper presents a low voltage-stress AC-linked charge equalizing system for balancing the energy in a serially connected, valve-regulated lead acid battery string using a modular converter that consists of multiple transformers coupled together. Each converter was coupled through an AC-linked bus to increase the overall energy transfer efficiency of the system and to eliminate the problem of the unbalanced charging of batteries. Previous solutions are based on centralized and modularized topologies. A centralized topology requires a redesign of the hardware and related components. It also faces a high voltage stress when the number of batteries is expanded. Modularized solutions use low-voltage-stress, double-stage, DC-linked topologies which leads to poor energy transfer efficiency. The proposed solution uses a low-voltage stress, AC-linked, modularized topology that makes adding more batteries easier. It also has a better energy transfer efficiency. To ensure that the charge equalization system operates smoothly and safely charges batteries, a small intelligent microcontroller was used in the control section. The efficiency of this charge equalization system is 85%, which is 21% better than other low-voltage-stress DC-linked charging techniques. The validity of this approach was confirmed by experimental results.

Prototype Combined Heater/Thermoelectric Power Generator for Remote Applications

This study presents a prototype thermoelectric generator (TEG) developed for remote applications in villages that are not connected to the electrical power grid. For ecological and economic reasons, there is growing interest in harvesting waste heat from biomass stoves to produce some electricity. Because regular maintenance is not required, TEGs are an attractive choice for small-scale power generation in inaccessible areas. The prototype developed in our laboratory is especially designed to be implemented in stoves that are also used for domestic hot water heating. The aim of this system is to provide a few watts to householders, so they have the ability to charge cellular phones and radios, and to get some light at night. A complete prototype TEG using commercial (bismuth telluride) thermoelectric modules has been built, including system integration with an electric DC/DC converter. The DC/DC converter has a maximum power point tracker (MPPT) driven by an MC9SO8 microcontroller, which optimizes the electrical energy stored in a valve-regulated lead–acid battery. Physical models were used to study the behavior of the thermoelectric system and to optimize the performance of the MPPT. Experiments using a hot gas generator to simulate the exhaust of the combustion chamber of a stove are used to evaluate the system. Additionally, potential uses of such generators are presented.

Online State-of-Health Estimation of VRLA Batteries Using State of Charge

This paper presents an online method for the estimation of the state of health (SOH) of valve-regulated lead acid (VRLA) batteries. The proposed method is based on the state of charge (SOC) of the battery. The SOC is estimated using the extended Kalman filter and a neural-network model of the battery. Then, the SOH is estimated online based on the relationship between the SOC and the battery open-circuit voltage using fuzzy logic and the recursive least squares method. To obtain the open-circuit voltage while the battery is operating, the reflective charging process is employed. Experimental results show good estimation of the SOH of VRLA batteries.

Pb-Ca-Sn-Ba Grid Alloys for Valve-Regulated Lead Acid Batteries

The effect of barium additives on the process of anodic corrosion of lead-tin-calcium alloys in a 4.8 М sulfuric acid solution was studied. Cyclic voltammetry, impedance spectroscopy, weight loss measurements and scanning electronic microscope analysis have allowed exploring the oxidation process and characterizing the formed corrosion layer. According to our results, barium introduction into lead-tin-calcium alloys increases their hardness, reduces their electrochemical activity, and improves their corrosion stability. Reduction of the calcium content in the alloy can be compensated by adding barium. Barium dopation at lead-tin-calcium alloys decreases the resistance of the oxide layer formed on the grid surface, in a deeply discharged state, and raises its resistance during floating conditions and at a charged state of the positive electrode.

Study of Thermal-Runaway in Batteries: II. The Main Sources of Heat Generation in Lead-Acid Batteries

Despite of the numerous research on thermal–runaway in valve regulated lead–acid batteries, its exact cause is not well known yet and it is not clear which physical phenomena contribute to thermal rise. To have a better understanding, the main sources of heat generation in lead–acid batteries are studied using the governing equations of battery dynamics derived in Part I. The governing equations including the conservation of energy are applied to different electrochemical reactions that take place during the overcharge of the battery. The reversible and irreversible heat sources of each reaction are determined separately. To investigate the heat generation contribution of each reaction, the governing equations are solved numerically using a two–dimensional thermal–electrochemical model. In this investigation, each term in the energy equation is calculated quantitatively in order to realize its contribution to heat generation. The numerical results show that beside Joule heating, only irreversibility contributes to heat generation which in turn results into temperature rise and the reversible part has no contribution.

The testing of batteries linked to supercapacitors with electrochemical impedance spectroscopy: A comparison between Li-ion and valve regulated lead acid batteries

For electric vehicles, a supercapacitor can be coupled to the electrical system in order to increase and optimize the energy and power densities of the drive system during acceleration and regenerative breaking. This study looked at the charge acceptance and maximum discharge ability of a valve regulated lead acid (VRLA) and a Li-ion battery connected in parallel to supercapacitors. The test procedure evaluated the advantage of using a supercapacitor at a 2 F:1 Ah ratio with the battery types at various states of charge (SoC). The results showed that about 7% of extra charge was achieved over a 5-s test time for a Li-ion hybrid system at 20% SoC, whereas at the 80% SoC the additional capacity was approximately 16%. While for the VRLA battery hybrid system, an additional charge of up to 20% was achieved when the battery was at 80% SoC, with little or no benefit at the 20% SoC. The advantage of the supercapacitor in parallel with a VRLA battery was noticeable on its discharge ability, where significant extra capacity was achieved for short periods of time for a battery at the 60% and 40% SoC when compared to the Li-ion hybrid system. The study also made use of Electrochemical Impedance Spectroscopy (EIS) with a suitable equivalent circuit model to explain, in particular, the internal resistance and capacitance differences observed between the different battery chemistries with and without a supercapacitor.

Research on Intelligent Controller of Solar Lighting System

After discussing the charging and discharging characteristics of valve regulated lead acid(VRLA) battery, we described the working principle of UC3906. Then designed the controller of 12V battery charge circuit, 12V battery discharge protection circuit and lamp detection control circuit. This controller achieved automatic switch of lighting system, it could efficiently charge the battery and avoid over-charge or over-discharge. The result showed that this controller extend the life of the battery.

Identification and remediation of sulfation in lead-acid batteries using cell voltage and pressure sensing

The operating environment, manufacturing variability, and use can cause different degradation mechanisms to dominate capacity loss inside valve regulated lead-acid (VRLA) batteries. If an aging mechanism for each cell can be identified in real-time, cell usage can be adjusted by the battery management system to optimize the performance and service life of the energy storage system. In this paper, the cell voltage and pressure of new and dead VRLA batteries are monitored during testing to determine the cause of death of the cells. The new cells have fairly uniform performance with limited signs of degradation while the cells in the dead battery have widely ranging performance, especially at the end of discharge and charge. Based on the measurement data, it appears that one cell died from sulfation and another three died of dehydration. The battery capacity is mainly dictated by the sulfated cell. A desulfation charging control scheme with pressure feedback is designed to break up hard sulfate and recover capacity while minimizing water loss by using low current charging. The capacity of the cell is recovered by 41% with minimal water loss, demonstrating the effectiveness of the desulfation charge controller.

Optimisation of a photovoltaic battery ultracapacitor hybrid energy storage system

Autonomous photovoltaic panels are intermittent sustainable energy sources which require energy storage to balance generation and demand, as photovoltaic generation is time and weather dependent. Traditionally batteries are the most common storage technology for photovoltaic systems. Photovoltaic batteries can encounter extended periods of low State of Charge (SOC), resulting in sulphation and stratification, reducing battery lifetime.Standalone photovoltaic systems are often used in remote areas away from the national grid for water irrigation system, requiring dc motor starting resulting in high inrush current, cathodic protection systems for oil and gas pipelines, emergency phones, warning signs, and telecommunication repeater stations, resulting in pulse discharging of the battery. A combination of depleted battery SOC and high burst current can result in premature loss of load due to stringent battery Low Voltage Disconnect (LVD) limits implemented by the battery management system.A combination of Valve Regulated Lead Acid (VRLA) batteries and ultracapacitors in a Hybrid Energy Storage System (HESS), which increases the power density of the overall system, is examined. Operating the ultracapacitor bank under high power conditions reduces the strain of large current extraction from the battery bank. The addition of the ultracapacitor bank presents the need for a methodology to optimise the photovoltaic system to prevent excess battery storage.This paper outlines the methodology utilised to optimise the combination of photovoltaic panels, batteries, and ultracapacitors for a given solar radiation and load profile employing Matlab software.

High-potential zinc–lead dioxide rechargeable cells

A zinc–lead dioxide rechargeable cell with an electrolyte composition of 1.5moldm−3 Zn(II), 0.5moldm−3 Na(I) and 0.3moldm−3 sulfuric acid is proposed and tested. The experimental results show that the open circuit potential of the zinc–lead dioxide cell is as high as 2.4V (20% higher than conventional lead-acid cells and 56% higher than recent copper–lead dioxide cells), while the average coulombic and energy efficiencies are 90% and 70%, respectively, over 90 cycles at 20mAcm−2. Furthermore, it is shown that the measured specific energy of the zinc–lead dioxide cell in a stack configuration is about 30% larger than that of a commercial valve regulated lead acid cell at the same operating conditions.

Electrochemical Principles as Applied to Grid Corrosion in Lead-Acid Batteries

Alloying constituents for lead alloys used for grids utilized in the manufacture of lead-acid batteries fall into two main categories: those with antimony and those without. The alloys without antimony can be further divided into those with calcium and those without, thus dividing the entire family of alloys into three main categories. This paper discusses the electrochemical principles that influence the progress of corrosion of these alloys in the lead-acid battery environment. Even as the alloy selected must meet the requirements of the application mode, it ultimately impacts the life expectancy of the battery. This review and discussion encompasses both the vented (or flooded) as well as the valve regulated lead acid (VRLA) battery types. Focus is on cast alloys in relationship to the grain structure and the inter-metallic phases present at the grain boundaries that lead to electrochemical disparity and corrosion, and the steps taken to control it.

Carbon Corrosion Mechanisms in Batteries during High-Rate, Partial State-of-Charge Cycling

Battery cycling profiles in hybrid electric vehicles have high currents both during charging, when the vehicle brakes are applied, and during discharging, when the vehicle accelerates. Cycle life in these high-rate, partial-state-of-charge (HRPSoC) applications is improved by adding conductive carbons with high surface areas to the negative active material. During charge, however, carbon can be oxidized by water to form soluble carbon monoxides such as formic acid. Further oxidation produces gaseous carbon dioxide at the positive electrode. As the internal cell pressure increases, it may force the vents open to release the carbon dioxide and other gases in the battery. Fortunately carbon dioxide formation is slowed by limited transport of soluble carbons from the negative to the positive plates. The valve-regulated lead-acid (VRLA) battery life is extended by carbon additions to the negative plate, but the ultimate cause of failure may become cell dry-out.

Mild HEV Performance at Micro Hybrid Cost - A Low Voltage Lead-Acid Approach

The Advanced Lead Acid Battery Consortium (ALABC) has since 2000 been demonstrating valve-regulated lead-acid (VRLA) batteries in hybrid electric vehicles and has shown that advanced designs can cope with this duty cycle with good reliability (1). This demonstration work has been done by converting existing vehicles and thus all work to date has utilized Japanese mild hybrids. The European market is coming at hybridization from a different direction, with the introduction of low-cost micro-hybrid stop/start systems, such as the BMW EfficientDynamics (2), in order to meet CO2 regulations. Recently Controlled Power Technologies (CPT) has been promoting an alternative way of achieving mild hybrid performance (3), which would meet projected CO2 regulations, at a fraction of the cost of the current Japanese approach. This new system would operate with advanced VRLA batteries at 12V or 48V and provides an opportunity for lead-acid to be at the leading edge of hybrid technology.

Experimental Investigation of H 2 Generator and PEM Fuel Cell as a Remote Area Back-Up Power

Abstract A reliable power is paramount and loss of power to communication equipment can mean loss of service to customers and loss of millions of dollars to companies. When the grid power is unavailable in remote areas there are variety of back-up electrical power systems like valve-regulated lead acid (VRLA) battery systems, engine-generator sets, ultra capacitors, flywheels, and new battery technologies that strive to provide back-up power. Hydrogen Energy and fuel cell technology compete with traditional technologies meeting back-up power requirements in stationary applications. Recent collaboration between Victoria University, Sustainable Energy Fuel Cells Australia (SEFCA) and Acta Energy has resulted in thorough laboratory testing for H 2 generation and data compilation of fuel cells in a back-up power operation in Power Systems Research Laboratory at Victoria University. The authors of this paper suggests that the use of EL100 H 2 generator and T-1000 1.2 kW PEMFC Power Generation System is capable to compete with traditional technologies to offer back-up power when there is no base load or PV or wind power. This paper presents the planning of laboratory testing, analysis and evaluation of the laboratory results. This paper also highlights the benefits of PEMFC system, EL100 H 2 generator and ReliOn's T-1000 PEMFC system. Currently it is expensive to run distance trucks requiring several site visits per year in order to refill the diesel or even carrying H 2 bottles to a rural site. This system generates H 2 on-site and can be implemented as a back-up power in telecommunication system like the Australian National Broadband Network (NBN) where there will be need for reliable back-up power supply since NBN will be rolling out several hundred points of presence (POP's).