Ana María Cao-Paz

A Multi-Point Sensor Based on Optical Fiber for the Measurement of Electrolyte Density in Lead-Acid Batteries

This article describes a multi-point optical fiber-based sensor for the measurement of electrolyte density in lead-acid batteries. It is known that the battery charging process creates stratification, due to the different densities of sulphuric acid and water. In order to study this process, density measurements should be obtained at different depths. The sensor we describe in this paper, unlike traditional sensors, consists of several measurement points, allowing density measurements at different depths inside the battery. The obtained set of measurements helps in determining the charge (SoC) and state of health (SoH) of the battery.

Resolution in QCM Sensors for the Viscosity and Density of Liquids: Application to Lead Acid Batteries

In battery applications, particularly in automobiles, submarines and remote communications, the state of charge (SoC) is needed in order to manage batteries efficiently. The most widely used physical parameter for this is electrolyte density. However, there is greater dependency between electrolyte viscosity and SoC than that seen for density and SoC. This paper presents a Quartz Crystal Microbalance (QCM) sensor for electrolyte density-viscosity product measurements in lead acid batteries. The sensor is calibrated in H2SO4 solutions in the battery electrolyte range to obtain sensitivity, noise and resolution. Also, real-time tests of charge and discharge are conducted placing the quartz crystal inside the battery. At the same time, the present theoretical “resolution limit” to measure the square root of the density-viscosity product (ρη) of a liquid medium or best resolution achievable with a QCM oscillator is determined. Findings show that the resolution limit only depends on the characteristics of the liquid to be studied and not on frequency. The QCM resolution limit for ρη measurements worsens when the density-viscosity product of the liquid is increased, but it cannot be improved by elevating the work frequency.

A B-learning new approach applied to a practical power electronics converters course

An Industrial Electronic discipline, involving different topics and technologies was designed to improve the sequence of activities within the available time and learning resources. The b-learning new methodology, applied in the University of Vigo, Spain, is composed of lectures, self-study sessions, quizzes, design problems, emulations, and laboratory sessions, integrated to achieve a better pedagogical environment. Most of the resources are available online without time restrictions, thus providing the students the opportunity to choose where and when they can learn, interact with the emulators, the remote laboratory and self-evaluate. Five flexible and powerful emulators have been developed for the buck, boost, buck-boost, forward and flyback converters. Emulation sessions provide a fast and easy path to understand the required concepts. The laboratory sessions are implemented by means of existing automatic test equipment (ATE), drive by a dedicated online server with new specific custom made software. The students provided positive evaluations of the methodology, and achieved a better degree of knowledge acquisition. Nowadays students from the University of Minho, Portugal, are also using remotely the set of resources available. The future work on this methodology will integrate the resources developed in both universities, to include more aspects of power electronics converters.

Density measurement into lead-acid batteries with multipoint optical fiber sensor

There are numerous applications for the use of leadacid batteries: automotive applications, telecommunications, UPS, remote-area power-supply systems, etc. Modern energy-storage applications require higher reliability than has been demanded in the past; in addition, systems have been developed for monitoring and managing the batteries so as to achieve duty in service. For determination of battery state, it is necessary to know the state of charge (SOC) and the state of health (SOH), one of the physical parameters with information about the SOC is the electrolyte density. An electrolyte density sensor must be able to measure the electrolyte density at different places because the battery-density varies with location. This paper presents a plastic optical fiber sensor developed for measuring in real time the electrolyte density into lead-acid batteries. The sensor measures the density at four different heights. The environment in the batteries that use an electrolyte with Sulfuric Acid (H2SO4) at an elevated temperature during the use process is very hard and the accuracy of the density readout must be maintained through the useful life of the vehicle. We have done an accelerated test to check the reliability sensor. The test duration was over one calendar year (9,552 hours) using a sensor with four optical fibers. For the test, the electrolyte acid density was set to 35%, and the temperature to 70 degrees Celsius. An electronic system for emission and detection of light collected data periodically to assess the transmission loss in the fibers as they aged. In this paper we present the test results.

Density and viscosity measurements in lead acid batteries by QCM sensor

In automotive applications, submarines and remote communication systems it is necessary to know the state of charge (SOC) of the batteries in order to manage them efficiently. Due to the acid concentration dependence of SOC, traditionally, density measurements are done in order to estimate it. But other parameters like electrolyte viscosity have highest changes with SOC than density. In this paper, a QCM (Quartz Crystal Microbalance) oscillator sensor for monitoring density and viscosity changes in lead-acid batteries is presented. The frequency shift is monitoring in solutions with H2SO4 concentration in the battery electrolyte range and the sensitivity and resolution of the sensor are determining for the application. Then, successful experiments are carried out by placing the quartz crystal inside the battery cell.

Monitoring of water uptake in anti-corrosion organic coatings using a quartz crystal oscillator sensor

Water absorption is an essential parameter to define the protection properties of anticorrosive paints. This parameter is often evaluated by means of the dielectric capacitance of the coating. The presence of water in the coating increases its dielectric constant. The semi-empirical Brasher-Kinsgbury equation [1] allows the estimation of a coatingpsilas water uptake through capacitance measurements. However, the capacitance of a coating depends, at least, on both the amount of water (volume fraction) and the shape of the water inclusions [2]. Brasher-Kingsbury approximations may result in highly inaccurate values. Therefore, it is interesting to have a direct measurement of the mass increment of the coating together with the time evolution of its dielectric capacitance. A stable quartz crystal oscillator sensor for measuring the water uptake in organic coatings was designed. The phase noise performance of the oscillator has been investigated in order to characterize the oscillatorpsilas resolution during the water uptake process. The result is a quartz crystal microbalance (QCM) sensor able to determine the rate and amount of water absorbed into anticorrosion cataphoretic coatings with a resolution of 360 pg/cm2 for one second sampling interval.

Fiber Optic Sensors for Diagnosis and Maintenance in Lead-Acid Batteries

Abstract This paper presents a fiber optic sensor for use in battery maintenance and also useful in determining the battery State of Health (SoH). The sensor was originally developed for electrolyte density measurements; the sensor comprises several plastic optical fiber sensors which measure the density of the electrolyte at different heights within the vessel of the battery. The sensor is based on light loss that occurs in the detection zone by means of the variation of the density of the electrolyte. This variation depends on the state of charge (SoC) of the battery at the height at which the sensor is placed and also depends on wear-out of battery. In summary, changes in the density of the electrolyte over time are an indicator of SoH. Strategic positioning of the measuring points of the sensor also allows measurements of other variables that facilitate maintenance: detection of low level of the electrolyte and the sediment of the active material that settles into space at the bottom of the cell.

Simultaneously measurement of frequency shift and series resistance changes of a quartz resonator using a miller QCM oscillator

In this work it is shown that a Miller quartz crystal microbalance (QCM) electronic oscillator circuit can be used to simultaneously measurement of the resonant frequency shifts and changes in the motional resistance of the resonator. In order to calibrate the sensitivity to variations in the series resistance of the resonator, an experiment was carried out with the resonator immersed in liquids at different concentrations of glycerol. Also the sensor system has been applied to control the series resistance during the water uptake in a cataphoretic organic coating. It was observed that the series resistance remains constant during the experiment in the absence of changes in the damping of the resonator (there are no viscoelastic changes in the coating). Moreover, we have studied amplitude fluctuations of the sensor system, determining the sensor resolution in the resistance measurements.