Lead Acid Battery Efficiency tracking System based on Microcontroller

 PART-2

Lead Acid Battery Efficiency tracking System based on Microcontroller

In this project we will develop the system which will monitor or track the health and efficiency of lead acid battery by measuring the internal resistance (impedance) of battery. As we know that the impedance (internal resistance of the battery changes or I can say that increases with the passage of time as the accumulation salt of plates of battery increases with the lapse of charging/ discharging cycles. In this project we will build a data acquisition system in which the microcontroller will continuously measure the internal resistance of battery and show the heath of battery concussively.

The lead acid battery which are the deep cycle batteries are designed so that maximum energy backup could be obtained from these by discharging the battery as much as possible like about 60%. It is normal thing that these types of battery which are used to provide a good backup battery time have thicker plates than the ordinary batteries. As a result these battery are more likely to get more and more salts on the plates, or the accumulation rate may be even rapid than usual. When sulfation starts occurring in the battery on the plates of battery the capacity start decreasing. The crystals are formed rapidly which decreases the active area of plates for chemical reaction with the electrolyte therefore the battery starts to deteriorate. The purpose to build a system after doing required study on subject is to determine the health of a deep cycle battery through the measurement the impedance which directly relate to the crystallization or sulfation in the battery. This project is divided in multiple phases. The first phase of the project is to learn the process of in which we will be able to measure the impedance of the deep cycle battery. This will be implemented by using the microcontroller and associated components. The measurement will be computed by applying required formulas and equation in the program running in microcontroller and at the end the results will be displayed at the LCD attached on front panel of the project. The useful information being displayed on the LCD will be value of voltages, internal resistance, and capacity and health of the battery. In the second stage of the project we will go to develop the desulfator which will keep the battery free of salt accumulation on plates of battery.

The Sulfation usually occurs if the temperature inside battery varies considerably and frequency is high as well intensity. The process of Sulfation becomes more rapid on high temperature of electrolyte because these are favorable condition for the solubility of the lead sulfate. The small lead sulfate crystals are dissolved during high-temperature periods and are slowly recrystallized into large crystals when the temperature is reduced. Cycling of electrolyte temperature is caused by ambient temperature changes or by heat generated during battery charge or discharge.

The sulfation of battery is describes as the salt is a white colored hard material enamel which covered the faces of the plates. This slat is now found out and called lead sulfate. The term Over sulfation is normally widely used in this field it is explained as it means too much sulfate forms in the active material of pate that the clean area of plate is considerably low which don’t fulfils the requirement at all. The sulfation can further be explained the battery should have these symptoms: (a) loss of capacity, (b) loss of voltage, (C) increase in internal resistance and (d) the decrease in sulfuric acid concentration. A desulphator is a circuit made for 12-volt of any other battery to make these salt dissolve back into the chemical electrolyte using resonant frequency. It has been noted that these type of circuit are more often applicable to medium sized batteries. It is further noted that the use of resonant frequency in battery reduces the need for equalization changes.

Some common modes of the lead acid battery failure are Loss of improper level of electrolyte, similarly the stratification of electrolyte and corrosion on plates especially the positive grid side plates. The loss of electrolyte or extended improper level of electrolyte which causes the air exposure to the plates results into the increase of internal resistance of the battery. If the situation in not get worst then by adding a distilled water can be a remedy to recover the batteries. If it is sealed battery then no way, this solution will not work. The electrolyte stratification means loss of capacity. If an overcharged battery had a gaseous reaction product at its electrodes, it will serve to stir the electrolyte. The other one is the positive grid corrosion. The mixture inside the battery if it has positive grid corrosion. The main solution for this problem is to maintain the rate of corrosion because as this increases the acidity of the electrolyte decreases. Flow chart to measure the internal impedance of lead acid battery:

Flow-Chart of Project for Lead Acid Battery Efficiency tracking System based on Microcontroller

The desulfator and battery condition monitoring system starts its functionality by first measuring the impedance (internal resistance of the battery) using dedicated sensor attached to the terminal of battery under operation. To accomplish the task, the measured values of the impedance, voltage and current are processed for obtaining meaningful results. This is done stepwise as, the subroutine in the program of microcontroller is called for acquiring the important parameters like voltage and current. Care is taken that the correctness of measurement are very important because error in measurement at this stage will cause larger confusion at the end. Therefore the microcontroller should be stable, the applied voltages to microcontroller unit must be stable and the signal shall be conditioned then we will be able read the voltages and current accurately. As we know that the battery voltages will be order of say 12volts and our microcontroller which has built-in ADC can accept voltages up to 05 volt DC. Therefore needs come to use some suitable circuitry that can transform the battery twelve volt to five accordingly. Here multiple options are available including use of voltage divider which is consisting of set of resistor. The value of resistor is selected carefully to have full range of expected voltage scanning.  For this an attenuator is here used to lower the input voltage to acceptable range and similarly the discharging current of the battery as well. Here this done using dedicated circuitry which will be provided at the end. At this stage we name this stage where the signal is being processed call the attenuator. Thus, the measured parameters e.g. the voltage and current from the attenuator is feed to the ADCs of the microcontroller to read, convert from analog to digital form and which will be processed latterly in the microcontroller. The internal resistance of battery will be calculated using the famous Ohm’s law. As we know that the Ohm’s law states that the voltage is equal to the current times the resistance. This principle will be used and the resistance will be calculated by dividing the battery voltage with the discharging current flowing on the circuit. On completion of measurement process of necessary inputs through a signal conditioning circuitry. A subroutine in the main program of the microcontroller of the system performs the necessary calculations. This data will have then statistical treatments for better results. The program written and burned into the microcontroller will perform calculation for the internal resistance in the battery which will be then related to the the overall health of the battery. This process will be continuing, the processed data including measured parameters will be saved into the memory of microcontroller for averaging the results. After a predefined time period the averaged results will be then displayed on a LCD attached at front panel so that the user can read the battery condition. The flowchart of system in above Figure shows the steps described above which are the part of project designing.

Hardware of desulfator and Lead Acid battery tester:

Lets discuss briefly the components being used in this project: It will include a suitable microcontroller, some analog components like resistors, capacitors, Op-Amps, and LCD. These components are being discussed very briefly one by one.

Microcontroller:

The microcontroller we are planning to use here for this project will be from MicroChip family and it will be PIV18452. It is very stable and suitable microcontroller for this application like it has built-in 10 bit ADCs, it has EEPROM, it has enough ROM and RAM to handle our code or program written for desulfator and battery monitoring purposes. The proper connections of input and output signals with the input/output PIN of Microcontroller are required which are describes in the schematic circuit diagram which will be provided at the end of this project. For the sake of simplicity of read, we can just focus that the input signal of voltages and discharge current after passing through the conditioning circuit will be directly feed to the ADC pins of MCU, LCD will be attached to other digital port of MCU.

Liquid Crystal Display (LCD):

Battery Health monitoring system’s output will be displayed on Liquid crystal display (LCD). In this project we have used an Alphanumeric 16 x 2 LCD display. This LCD has 16 pins which are consisting of two sets like control and data: the main function of these pins are register select, read/write, enable, data, LED backlight, power supply and display contrast pins. The input biasing voltage required for the proper functioning of the LCD display is only 05V DC. The results of the computations will be displayed on LCD as an output for assistance of user.

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