An intelligent lead acid battery management system for solar and off-peak energy storage systems.

The depleting energy resources with every passing day generate a need to innovate the electrical system. The aggravating dependence on power systems and the considerable increase in the existing uses (electric coolers, air conditioners, electric heaters and other uses like hybrid electrical vehicles

Project Title

An intelligent lead acid battery management system for solar and off-peak energy storage systems.

Project Area of Specialization

Internet of Things

Project Summary

The depleting energy resources with every passing day generate a need to innovate the electrical system. The aggravating dependence on power systems and the considerable increase in the existing uses (electric coolers, air conditioners, electric heaters and other uses like hybrid electrical vehicles and heat pumps) forces the control of power system, thereby making the need of developing renewable resources more imperative. Taking into account the renewable sources and analyzing their pros and cons proves solar energy as the best and most suitable alternative to replace fossil fuel as the major energy source considering both technology and installation cost.
It is renewable at absolutely no cost to supply in addition, its eco-friendly nature, durability, extreme reliability and high return on investment justifies it more as the top alternative to fossil fuels. The world pollution is getting worse. Any effort that can reduce the pollution to the environment helps to save the earth. Owing to this, solar energy offers a clean, renewable source of power. For stand-alone power system applications, micro-girds which combine several localized systems into a small power network have drawn recent attention.
Thus making an energy efficient management system to reserve this resource and ensure an uninterrupted supply to the user is main motive of this SDP. This is ensured through devising a battery management system to the generic solar panel and configuring the system over IoT for easy accessibility. The project aims to develop an intelligent battery management system that counts all the factors preserving the battery strength to its maximum keeping a check on its overcharging, depletion, temperature etc. Moreover, the system is not only capable of generating power for itself however when the generated power exceeds the maximum charging limit of the battery it feeds the rest to the local utility grid.
So this project aims to design and develop a smart controller based intelligent lead acid battery management system for solar and off-peak energy storage system through IoT based system to increase the ease of accessibility.

Project Objectives

Aims & Objectives
To design and develop a smart controller based intelligent lead acid battery management system for solar and off-peak energy storage system through IoT based system to increase the ease of accessibility.    
    
Objectives
?    Smart load management
?    Smart battery management system 
?    Making solar energy an effective approach
?    Cost effectiveness 
?    Uninterruptible power supply
 

Project Implementation Method

This system comprises of an intelligent battery management system (BMS) that is operated by the microcontroller. The system includes the following main parts:
?    A solar cell array, with maximum power point tracking (MPPT).
?    A BMS and a battery bank to optimize the energy storage capacity a bidirectional inverter connected to the grid.
?    An IoT based communication interface to monitor operation.
The following flowsheet describes the implementation method of the project.

 

Battery Management system:
The main objective of this system to make a battery energy management system that fits into a solar power system that is practical and useful in the real world. The battery bank can store electricity energy that is delivered from the solar array or the power grid. It is an indispensable unit when the solar energy system is disconnected from the grid or for off-peak energy storage.
The battery we will use in the project is LEAD ACID BATTERY due to its low maintenance and cost effectiveness. It is one of the most common types of rechargeable batteries in the world.
The BMS contains a central and one or more local modules, and each local has two functional units : an electronic control unit (ECU) and an electronic equalization unit (EQU). The ECU measures the cell voltages and sets the EQU to equalize the voltage levels among the individual cells.
Battery Monitoring
BMS monitor’s the state of the battery by various items:
Voltage?    : total voltage, voltages of individual cells, minimum and maximum cell voltage.
Temperature?    : average temperature
State of charge (SOC)), to indicate the charge level of the battery
State of health (SOH), a variously-defined measurement of the remaining capacity of the battery as % of the original capacity
?    State of Safety (SOS)
Current?    : current in or out of the battery
Battery Protection
BMS protect its battery by preventing it from operating outside its safe operating area, such as
?    Over-voltage (during charging)
?    Under-voltage (during discharging)
?    Over-current (may be different in charging and discharging modes)
?    Temperature controls 
?    Ground fault or leakage current detection (system monitoring that the high voltage battery is electrically disconnected from any conductive object touchable to use like vehicle body)
It BMS may prevent operation outside the battery's safe operating area by: 
?    Including an internal?     ?    switch (such as a?     ?    relay or?     ?    solid state device?    ) which is opened if the battery is operated outside its safe operating area
?    Requesting the devices to which the battery is connected to reduce or even terminate using the battery.
?    Actively controlling the environment, such as through heaters, fans, air conditioning or liquid cooling.
 

Benefits of the Project

The proposed SDP is intended to provide stored energy during high electric power demand periods. During the day time, the system stores the energy generated from the solar panels in the battery bank for consumption in the evening. At midnight, the system also charges the battery by importing cheap energy from public utility power grid. This provides the base energy for the next day’s load. The strategy of the ?Off-Peak Energy Management System is to store energy during low load periods and release energy during high demand periods.
The time when energy is to be released is from 6 to 8 a.m. in the morning and from 5 to 7p.m. in the evening when electric power demand is highest. 

Practical applications of BMS include:

• Illumination (lighting) control.
• Electric power control.
• Heating, ventilation, and air conditioning.
• Security and observation.
• Access control.
• Fire alarm system.
• Lifts, elevators etc.
• Plumbing.

Technical Details of Final Deliverable

Techincal details of final deliverable include:

    Measuring Battery Voltage
An op amp within the IC TL494 is used to monitor voltage across the battery. The inverting pin is connected to Vref, 5V. A comparison between voltages at inverting & non-inverting pins is done by using a potentiometer at Pin # 1, i.e the non-inverting pin. The one side of potentiometer is connected to the rectified voltage across the load.
The setting of potentiometer is set such that when the voltage across load is 
14.2V, it stops the IC to generate the duty cycle. Basically load voltage becomes 14.2V, the voltage at non-inverting terminal becomes 5.01V that exceeds the voltage at inverting terminal causing the op-amp to turn on thereby the IC stops generating duty cycle.

Current Sense
Another op-amp within the IC TL494 is used to monitor current through the battery. The inverting pin is connected to anode of diode 1N4148, with a resistor 1k in series with it The other end of 1k resistor is connected to 5V reference pin. In this way, a voltage drop of 0.68V occurs across the diode, at pin 15, inverting pin of IC. A comparison between voltages at inverting & non-inverting pins is done by using a potentiometer at Pin # 16, i.e the non-inverting pin. The one side of potentiometer is connected to a shunt resistor in series with the rectified voltage across the load. The setting of potentiometer is set such that when the voltage across load is 1V, it stops the IC to generate the duty cycle. Basically when the voltage at non-inverting terminal becomes 0.6501V that exceeds the voltage at inverting terminal causing the op-amp to turn on thereby the IC stops generating duty cycle. In this way, current is monitored.
Temperature Monitoring 
Temperature sensors monitor each cell for energy-storage-system (ESS) applications or a grouping of cells for smaller and more portable applications. Thermistors powered by an internal ADC voltage reference are commonly used to monitor each circuit’s temperature. In addition, an internal voltage reference helps reduce inaccuracies of the temperature reading versus environmental temperature changes.
Fuel-Gauge/Current Measurements 
The fuel-gauge functional block keeps track of the charge entering and exiting the battery pack. Charge is the product of current and time. Several different techniques can be used when designing a fuel gauge.
Communication interface:
To make the entire system ‘smart’, and innovative, the results will be uploaded on either a site or an app will be developed to monitor the real-time system information and to observe the data changes over time. Both the approaches will use IoT technology for the communication process. we will use Raspberry-pi module for communications and THINK SPEAK for uploading data.

Final Deliverable of the Project

Hardware System

Core Industry

Energy

Other Industries

Core Technology

Internet of Things (IoT)

Other Technologies

Sustainable Development Goals

Affordable and Clean Energy

Required Resources

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