VRLA Research Articles

VRLA Battery Virtual Reference Electrode: Battery Float Charge Analysis

This paper investigates the problems and deficiencies with present valve-regulated lead-acid (VRLA) battery float charge techniques. The requirements and goals of float charge are identified, and a mechanism for assessing the achievement of these goals is provided. An electrical equivalent model of a VRLA cell's float charge operational region is developed. This model replicates both the steady-state and transient responses of a float charging VRLA cell. Based on the response of each electrode within a cell to an applied stimulus, a simple test-and-analysis procedure is developed. This procedure extracts reference-electrode-like polarization information from any conventional 2 V VRLA cell in float service. This test procedure is applied to the terminals of a standard cell, and does not require any physical modification to the cell.

Failure modes of valve-regulated lead-acid batteries for electric bicycle applications in deep discharge

The 36 or 48 V valve-regulated lead-acid (VRLA) battery packs have been widely applied to the power sources of electric bicycles or light electric scooters in China. The failure modes of the 12 V/10 Ah VRLA batteries have been studied by the cycle life test at C 2 discharge rate and 100% depth of discharge (DOD). It indicates that the main cause of the battery failure in this cycle duty is the softening and shedding of positive active mass (PAM) rather than individual water loss, recombination efficiency or sulfation, etc. When the electrolyte saturation falls to a certain extent, the high oxygen recombination current leads to the depolarization of the negative plate and the shift of the positive plate to a higher potential. The violent oxygen evolution accelerates the softening of PAM and the end of cycle life.

The Application of Valve-Regulated Lead Acid Batteries to Wind Power Generation System

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Charge regimes for valve-regulated lead-acid batteries: Performance overview inclusive of temperature compensation

The main battery type employed in standby applications is the valve-regulated lead-acid (VRLA) battery. Float charging is normally used to maintain the battery in its fully charged state, however, float charging has limitations that can damage the battery and shorten its life. New charge regimes have evolved in recent years to tackle the intrinsic problems of float charging. The intermittent charge (IC) regime and the interrupted charge control (ICC) regime have been developed to prolong the service life of the battery in standby applications. The battery is normally maintained in the standby mode for a long period of time and there are infrequent discharge tests to verify the efficacy of the battery. Hence, the service life of the battery is highly correlated to its charge regime. This paper reviews the charge regimes for VRLA batteries, and assesses their charging performance and their impact on the service life of the battery. Recognising that temperature plays a significant role in battery operation, temperature compensation schemes are described for different charge regimes.

The Optimization of Gel Electrolytes on Performance of Valve Regulated Lead Acid Batteries

The gel electrolytes were prepared with sulfuric acid and phosphoric acid, where hydrophilic fumed silica was used as a gelling agent. The influences of gel electrolyte on performance of the valve regulated lead acid (VRLA) batteries were investigated employing capacity tests, electrochemical impedance spectroscopy and scanning electron microscopy. The initial capacities of the sulfuric gel VRLA batteries were higher than that of phosphoric gel VRLA batteries. The sulfuric gel VRLA battery using 1.210 specific gravity of sulfuric acid with hydrophilic fumed silica exhibited the highest capacity of 0.828Ah. In the impedance measurements, the ohmic and charge transfer resistances for the phosphoric gel VRLA batteries were higher than that of sulfuric gel batteries. The morphology of electrodes of phosphoric gel VRLA batteries were more deteriorated in the SEM image.

Effects of preparation condition and particle size distribution on fumed silica gel valve-regulated lead–acid batteries performance

The effects of three types of fumed silica on the electrochemical properties of gelled electrolytes have been investigated by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), transmission electron microscope (TEM) and the Brunauer, Emmett and Teller (BET) technique. The CV and EIS results show that a moderate mechanical dispersion of fumed silica in the H 2SO 4 solution has important effects on the electrochemical properties of the gelled electrolyte. The optimal mechanical dispersion time is closely related to the operating temperature during preparation of gel, as well as the silica particle size and its distribution. A high stirring rate improves the electrode capacity and decreases the viscosity of the gelled electrolyte. With moderate mechanical dispersion, gelled electrolytes prepared from different fumed silica particles exhibit equal electrode capacities.

80Ahリチウムイオン電池を適用したラックマウント型直流電源システムのフィールド試験

Using an industrial lithium-ion battery that has higher energy density than conventional valve-regulated lead-acid batteries, a rack-mounted DC power supply system was assembled and tested at a base transceiver station (BTS) offering actual services. The nominal output voltage and maximum output current of the system are 53.5 V and 20 A, respectively. An 80-Ah lithium-ion battery composed of 13 cells connected in series was applied in the system and maintained by the floating charge method. The DC power supply system was installed in a 19-inch power rack in the telecommunications equipment box at BTS. The characteristics of the 80-Ah lithium-ion battery, the specifications of the DC power supply system, and field-test results are presented in this paper. \copy 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(3): 1–8, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21067

Работа свинцово-кислотного аккумулятора в условиях постоянного недозаряда

Effect of graphite addition to negative material and of new material of negative grids of VRLA batteries have been studied for partial-state-of-charge applications.

Comparative study of lead-acid batteries for photovoltaic stand-alone lighting systems

The lead-acid battery is often the weakest link in photovoltaic (PV) installations. Accordingly, various versions of lead-acid batteries, namely flooded, gelled, absorbent glass-mat and hybrid, have been assembled and performance tested for a PV stand-alone lighting system. The study suggests the hybrid VRLA batteries, which exhibit both the high power density of absorbent glass-mat design and the improved thermal properties of the gel design, to be appropriate for such an application. Among the VRLA-type batteries studied here water loss for the hybrid VRLA batteries is minimal and charge-acceptance during the service at high temperatures is better in relation to their AGM counterparts.

Application of a novel gelled-electrolyte in valve-regulated lead-acid batteries with tubular positive plates

A polysiloxane-based gel electrolyte (PBGE) was prepared and used as a novel gel electrolyte in valve-regulated lead-acid (VRLA) batteries with tubular positive plates. Cyclic voltammetry (CV) and scanning electron microscopy (SEM) indicated that PBGE is more stable than fumed-silica gel electrolyte (FSGE). The properties of AGM (absorptive glass mat)-PBGE and PVC-FSGE tubular batteries were investigated by electrochemical techniques. The results showed that the AGM-PBGE tubular batteries have higher initial discharge capacity and better high-low temperature performance than PVC-FSGE. The improved electrochemical performance of the AGM-PBGE batteries may result from the high charge efficiency and the open three-dimensional network structure of PBGE. SEM and X-ray diffraction (XRD) spectroscopy showed that PBGE facilitates the conversion of the active-mass to lead dioxide, presenting a high formation efficiency. The addition of PBGE instead of FSGE not only simplifies the manufacturing process of tubular gel batteries, but also improves the utilization efficiency of positive active material (PAM), thus enhancing the battery performance and reducing the manufacturing cost.

Stored energy - Short-term and long-term energy storage methods

This paper deals with the short-term and long-term energy storage methods for standby electric power systems. Stored energy is required in uninterruptible standby systems during the transition from utility power to engine-generator power. Various storage methods provide energy when the utility source fails. For batteries in cycling duty, Li-ion and Ni-MH cells are coming into wide use to displace VRLA batteries. For float duty, VRLA and NiCd batteries predominate. Flywheel-generator units are being offered to replace batteries in UPS. Fuel cells require a warm-up time and, hence, are suitable for long-term operation. Ultracapacitors are proposed to replace batteries for short-term discharge. CAED and hydrogen energy storage are suitable for large projects.

Lead-acid and lithium-ion batteries for the Chinese electric bike market and implications on future technology advancement

China has been experiencing a rapid increase in battery-powered personal transportation since the late 1990s due to the strong growth of the electric bike and scooter (i.e. e-bike) market. Annual sales in China reached 17 million bikes year −1 in 2006. E-bike growth has been in part due to improvements in rechargeable valve-regulated lead-acid (VRLA) battery technology, the primary battery type for e-bikes. Further improvements in technology and a transition from VRLA to lithium-ion (Li-ion) batteries will impact the future market growth of this transportation mode in China and abroad. Battery performance and cost for these two types are compared to assess the feasibility of a shift from VRLA to Li-ion battery e-bikes. The requirements for batteries used in e-bikes are assessed. A widespread shift from VRLA to Li-ion batteries seems improbable in the near future for the mass market given the cost premium relative to the performance advantages of Li-ion batteries. As both battery technologies gain more real-world use in e-bike applications, both will improve. Cell variability is a key problematic area to be addressed with VRLA technology. For Li-ion technology, safety and cost are the key problem areas which are being addressed through the use of new cathode materials.

Effects of electrolyte stratification on performances of AGM valve-regulated lead-acid batteries

Two absorptive glass mat (AGM) valve-regulated lead-acid batteries with concentration and saturation stratification were simulated. Results indicate that the concentration stratification makes the active mass (AM) in lower part discharge deeply, which results in more irreversible sulphate on the negative plate because of inefficient recharge. In saturation stratification, more AM is also discharged in lower part, but the high oxygen recombination and undercharge in the upper part of the negative plate also leads to its sulphation. When the battery is in short-time rest state, the self-charge process occurs in the upper part and self-discharge process in the lower part of the same plate, but the processes differs with rest continuing. All these make the negative plate sulphation.

A novel PEO-based composite polymer electrolyte with absorptive glass mat for Li-ion batteries

A novel PEO (polyethylene oxide)-based composite polymer electrolyte (CPE) using absorptive glass mat (AGM) as filler was prepared and characterized. Scanning electronic micrograph (SEM) images showed that the addition of Li salt and modified AGM may improve the surface morphology of CPE. The results of Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeters (DSC) indicated that the inclusion of LiClO4 salt and the addition of AGM filler can reduce the crystallinity of PEO. It was concluded that the addition of AGM plays two roles in PEO-based CPEs, namely, interruption of the PEO recrystallization and reinforcement of CPEs, accordingly enhancing room temperature ionic conductivity of CPEs and improving its mechanical strength and electrochemical stability at high temperatures.

Idling-stop vehicle road tests of advanced valve-regulated lead-acid (VRLA) battery

The results of road tests on valve-regulated lead-acid (VRLA) batteries in an idling-stop (stop and go) vehicle are reported. Idling-stop systems are simple systems to improve fuel economy of automobiles. They are expected to spread widely from an environmental perspective. Performances of a conventional flooded battery, a conventional VRLA battery, and an improved VRLA battery were compared in road tests with an idling-stop vehicle. It was found that the improved VRLA battery was suited to idling-stop applications because it had a smaller capacity loss than the conventional flooded battery during partial-state-of-charge (PSoC) operation. The positive grid was corroded in layers, unlike the usual grain boundary corrosion of SLI battery grid. It is because the corrosion proceeded mainly under PSoC conditions. The corrosion rate could be controlled by potential control of positive plates.

Spiral wound valve-regulated lead-acid batteries for hybrid vehicles

Future vehicle applications require the development of reliable and long life batteries operating under high-rate partial-state-of-charge (HRPSoC) working conditions. This paper updates work carried out to develop spiral wound valve-regulated lead-acid (VRLA) batteries for vehicles with different hybridisation degrees, ranging from stop-start to mild hybrid applications. Former work on design optimisation and active material formulations has been implemented in two spiral wound VRLA batteries, rated 12 V 50 Ah and 6 V 24 Ah, and these two products are currently being tested both in benches and in vehicles with different hybridisation degrees within a demonstration project funded by the Advanced Lead Acid Battery Consortium and in collaboration with several European vehicle and electrical component manufacturers.

Advanced valve-regulated lead-acid batteries for hybrid vehicle applications

Future vehicle applications require the development of reliable and long life batteries operating under high-rate partial-state-of-charge (HRPSoC) working conditions. Work presented in this paper deals with the study of different design parameters, manufacturing process and charging conditions of spiral wound valve-regulated lead-acid (VRLA) batteries, in order to improve their reliability and cycle life for hybrid vehicle applications. Test results show that both electrolyte saturation and charge conditions have a strong effect on cycle life at HRPSoC performance, presumably because water loss finally accelerates battery failure, which is linked to irreversible sulphation in the upper part of the negative electrodes. By adding expanded graphite to the negative active mass formulation, increasing the electrolyte saturation degree (>95%) and controlling overcharge during regenerative braking periods (voltage limitation and occasional boosting) it is possible to achieve up to 220,000 cycles at 2.5% DOD, equivalent to 5500 capacity throughput. These results could make lead acid batteries a strong competitor for HEV applications versus other advanced systems such as Ni–MH or Li-ion batteries.

Remote monitoring of VRLA batteries for telecommunications systems

This paper describes a remote monitoring system that can be set up in an operating center to monitor the state of valve regulated lead acid batteries (VRLA) used as a backup power supply for telecommunications. This system has a battery voltage monitoring function, a lifetime prediction function based on ambient temperature, and a discharge circuit diagnosis function. In addition, the system can be equipped with an internal resistance measurement function and an electrolyte leakage detection function to further insure power-supply reliability. Various states of batteries observed with the system are transmitted to the remote operating center by a remote monitoring function. This function enables obtaining immediate information about the condition of batteries and helps to avoid unexpected failures.

Modeling of the charge acceptance of lead–acid batteries

This paper presents a model for flooded and VRLA batteries that is parameterized by impedance spectroscopy and includes the overcharging effects to allow charge-acceptance simulations (e.g. for regenerative-braking drive-cycle profiles). The full dynamic behavior and the short-term charge/discharge history is taken into account. This is achieved by a detailed modeling of the sulfate crystal growth and modeling of the internal gas recombination cycle. The model is applicable in the full realistic temperature and current range of automotive applications. For model validation, several load profiles (covering the dynamics and the current range appearing in electrically assisted or hybrid cars) are examined and the charge-acceptance limiting effects are elaborately discussed. The validation measurements have been performed for different types of lead–acid batteries (flooded and VRLA). The model is therefore an important tool for the development of automotive power nets, but it also allows to analyze different charging strategies and energy gains which can be achieved during regenerative-braking.

Investigation and application of polysiloxane-based gel electrolyte in valve-regulated lead-acid battery

Polysiloxane-based gel electrolyte (PBGE) is prepared and investigated as a new gel electrolyte for valve-regulated lead-acid (VRLA) batteries. PBGE particles, characterized by means of Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV) and scanning electron microscopy (SEM), reveal good stability and their particle sizes are 30–50 nm. The initial cyclic properties of the absorptive glass mat (AGM)–PBGE and AGM–colloid silica gel electrolyte (CSGE) hybrid batteries are investigated by electrochemical techniques, scanning electron microscopy and X-ray diffraction (XRD). The addition of PBGE improves the utilization efficiency of positive active material (PAM) in AGM–PBGE hybrid batteries and thus enhances the batteries capacity compared with the AGM–CSGE reference batteries. Cyclic overdischarge tests show that the AGM–PBGE hybrid batteries have superior recharge and discharge during partial-state-of-charge (PSoC). It is also found that the greatly enhanced electrochemical performance of the AGM–PBGE batteries may be due to higher charge efficiency, good conductivity with lower internal resistance and the open three-dimensional network structure of the polyelectrolyte. The analysis results of SEM and XRD indicate that softening and shedding of positive active material are the main causes of failure for the two hybrid batteries.