Projects:2019s2-25101 Logging of Battery Performance and Modelling of Batteries

Nowadays, due to limitation resource (peak-oil) and CO2 pollution that been affecting climate changes are getting worse. Those factors are forcing engineers to ensure making good use of renewable energy to overcome those problems. After that, this also will lead to better development of renewable energy systems. Thus, the method of energy storage and energy transportation will be upgraded at no time that will increase the efficiency of renewable energy. This project also will be discussing regarding type pf chemical, the chemical reaction inside a battery and structure of the battery.

Unfortunately, there are several problems that need to be solved which are the need to determine what is the optimum parameters needed to improve short term benefits and long-term cost of the battery. Operators will need to determine cycles of the batteries which are State of Charge (SoC) and Depth of Discharge (DoD) to improve the performance of the battery and also the efficiency of the battery. At the same time, to determine a suitable life cycle of a certain battery, the operators also need to find the most efficient technology of battery to help to improve the performance of the battery. By deciding those parameters, will help to increase the State of Health (SoH) of the battery.

As a conclusion, this project will be divided into two main parts:

• Logging curve behaviors of batteries under the State of Charge (SoC) and Depth of Discharge (DoD) over a long period of time to estimate the State of Health (SoH) of the battery.

• To use the Simulink model to get data to be compared with historical data from the Australian power network to help in optimizing between short term and long-term benefits for the battery system.

Introduction

In this project, there will be determined about the performance of the battery. There also will be researched about the detail of several types of batteries that been used in the household power industry. After that, there will also be testing regarding the cycle of batteries from State of Charge (SoC) and Depth of Charge (DoD). Thus, all those aspects also will be compared with existing products such as efficiency and energy density that been produced by the battery.

Furthermore, this project also will help to reduce the average power demand cost that is by comparing the data from AEMO website to determine when the exact time for the battery storage to discharge and charge. Based on the previous statement, this will be required to use a good controller system to make a good switching state toward battery storage.

Project team

Project students

• Mohammad Adib Akhmal Ahmad
• Wan Mohd Aqil Arfan Bin Wan Mohd Amal
• Jessyiana Anak Musa

Supervisors

• Dr. Andrew Allison
• Prof. Derek Abbott

Objectives

• Log behavior of batteries

• Estimate parameters to implement to Simulink battery model

• Literature review about battery aging

• Perform series simulations of batteries

• To extend the life of the battery

Background

Existing Product

Tesla Powerwall

• Technology Used = Li-ion NMC

• Voltage output range = 350 - 450 V

• Maximum discharge rate = 3.3 kW

Tesla Powerwall 2

• Technology Used = Li-ion NMC - Panasonics

• Voltage output range = 230V

• Maximum discharge rate = 5.0 kW

LG Chem RESU

• Technology Used = Li-ion NMC

• Voltage output range = 51.8 VDC

RESU IOH

• Technology Used = Li-ion NMC

• Voltage output range = 350 - 450 VDC

Sonnen Batteries ECO

• Technology Used = Lithium LFP - Sony

Technical Challenges

Battery health

This section will be used to determine the state of health of the battery. This parameter been defined as one of the main challenges for this project due to the time constrain to undergo enough experiment to observe the effect of the duty cycle with the state of health of the battery compared with the ideal state of health. Thus, this problem can be solved by referring toward the existing article that been using the same type of battery to see the behaviour of the battery.

Realistic data on household demand

This section also been defined as one of the challenges in this project because this data can as one of the vital parameters to ensure the reliability of the system. This is because when this project been supplied with an accurate data, it can help to reduce the demand cost during peak hour, and this also will need an extra precise switching device in the project.

Temperature regulation

Temperature regulation also can be classified as one of the hardest components to be control in this project. This section also very crucial in this project because of different operating temperature can affect the overall performance of battery. So, a proper cooling system need to be provided in this project to ensure the battery can be operate at optimum level at all time. Besides, a proper casing also needs to be built to make sure the momentum from explosion produced by battery can be reduced.

Suitable switching mode

Switching mode also can be quite challenging because of to make an efficient charging and discharging controller, good components or sensor need to be found to give an accurate measurement. This is because controller need a precise data to know the exact time to make a transition between charging into discharge state. This will need a good component to ensure that process can be execute without any problem such as converter. Thus, when the system got a proper switching function, it can also help to improve the state of health of the battery and can avoid from the battery undergo thermal runaway condition.

Data logging during charging and discharging process

This part also vital a vital contribution toward the project which will help to determine whether the system been design properly or not. This section will need a precise measure and a good platform such as website to make a schedule update toward the charging and discharging value of the battery. Thus, a good connection between the battery system and the controller need to check properly to ensure an accurate data can be collected precisely.

Block Diagram

Figure 1: Block Diagram

Figure 1 shows the flow of the proposed project that will be planned to be built through this entire project. Basically, the circuit will be start from the supply which basically will be come from power generator from the lab equipment. After that, Raspberry Pi will act as the main controller of the system which is will control all the process in the system such as temperature regulation, state of charge, state of discharge, depth of discharge and data logging from the behaviours of the battery. Besides, converter will be used to act as switching device that will allow the interaction between battery, load and supply can be control efficiently. Lastly, Raspberry pi will collect the data from the state of charge and state of discharge to observe the state of health of the battery throughout the whole project.

Method

Introduction

Figure 2: Project Circuit

This section will be used to identify the work that been taken by group project and the process that will be taken by group project to solve the knowledge gap problem. As been mentioned in knowledge gap section which to know the detail of Kalman Filtering method that will be used to estimate the state of charge, state of discharge and state of health of the battery.There are several methods can be used to solve this knowledge gap which is full design of Simulink that will control the charging and discharging process. This also will help to put Kalman Filtering function in these Simulink model to estimate the state of charge and state of discharge rate of the model and this function also will help to estimate the overall state of health of the battery by collecting several data from the simulation.These steps will be proceeded after all the behaviour of the battery had been understand by group project which is at the moment voltage and current integrating over time method been used to determine the state of charge and state of discharge of the system. These steps been used by measuring the value of voltage and current over time period during charging and discharging process to get the curve of voltage and current.

State of Charge (SoC) and Depth of Discharge (DoD)

Level of charge to relative capacity of battery

Method to determine SoC and Depth of Discharge (DoD)

Chemical method

Reaction of electrolyte of batteries

Voltage method

Observe the voltage and current curve of battery during SoC

Current Integration method

Measure current of battery and integrate with time

Kalman Filtering method

Predict over-voltage due to current using electrical model

State of Health

This section will be used to explain about how to measure the overall condition and performance of the battery during operation and resting mode. State of health of the battery can be measure by comparing to the ideal condition or ideal state of the battery which is 100%. Usually all the state of health of the battery will be 100% during the time of manufactured and the state of health will be decreased over time of the usage. Battery management system very crucial to ensure the state of health of the battery will remain in a good condition in a long time. The ideal state of health only until 85% of its ideal state. This is to ensure the performance of the battery can always been in the optimum state. There are several main aspects that will be affected the state of health of the battery which are: -

Internal resistance

The internal resistance will give a big contribution toward the state of health and the performance of the battery. This is because the internal resistance will be increase when the electrolyte of the battery in a bad condition.

Number of charge and discharge cycle

This aspect also will affect the state of health of the battery because of when the number of charge and discharge increased, the age of the battery also will keep increasing.

Operating Temperature

This will be one of the most crucial aspect that needed to consider and control during operating the battery storage especially during charging and discharging process. This is because when the operating temperature had exceeded the ideal operating temperature of the battery, this will make the internal resistance of the battery will keep increasing and the efficiency of the battery also will be decreased. After that, this also might be dangerous when operating with the battery that have high energy density such as lithium ion battery that might be exploded.

Total energy charge and discharge

This aspect also very important in the battery management system. This is because the total energy that been charge and discharge need to be measured to ensure the safety for the user. This is because when the rate of charge and discharge of the battery had been exceeded, it will cause the battery swelled or exploded. Besides, this aspect also needs to be monitored to ensure the operating temperature always in the ideal state. The complete datasheet of the battery needs to be referred to make a good battery management system during charging and discharging process.

Results

ADC Configuration

Figure 2: ADC calibration result

Figure shows the output of ADC that been printed out in the terminal that shows varies number of decimals. Those number been used to represent the value of voltage through potentiometer. This value can be varying when the knob of potentiometer been changed. Based on the value that been displayed by the ADC, the calibration can be done by collecting the data and get the mean value of the voltage range. By getting the mean value of the voltage and ADC value will make easier to determine the value of the voltage and the value of ADC will be used when the exact voltage been used for the data logging process

Simulation

Figure 3: simulation

Basically, this simulation been connected with the constant load. The lithium ion battery been used in this simulation that been set with 200V for the nominal voltage and 6.5Ah for the nominal capacity of the battery. Based on the output waveform, the battery will be in charging mode when the SoC had achieve 20% which is the DC machine will provide the negative load torque to charge the battery. Then, when the SoC of the battery had been exceed 90%, the negative load torque been disconnected, and the battery will be connected with the constant 50A constant load. By referring to the output waveform above, shown that this is one type of the hybrid system. This simulation also been used relay to control the switching state of the charging and discharging state of the battery. This simulation can be upgraded in the future by adding the Kalman filtering function in the simulation to be able the system to make estimation about when the suitable time for the battery to be charged and discharged. This function also will help to provide the data for state of health of the battery.

Analysis

• Raspberry Pi

This section can be defined as one of the vital parts of this system which will be used as the main controller that will be monitored all the behaviour of the system during charging and discharging process. During this current progress this controller been used to make a basic switching process and to know how to calibrate the ADC chip that will able to measure the value of voltage and current across the battery during charging and discharging process. For future progress, this section will be planning to make a direct connection with the other component to do a data logging process. Besides, this controller also will be used crontab function to do schedule switching mode for the battery system that will help to improve the reliability level of this system.

• Analog and Digital Conversion process

Currently, this process be used to measure the basic behaviour of the battery during charging and discharging process. This process basically will measure the voltage and current curve of the battery to fulfil the procedure of voltage and current integrating overtime process to determine state pf charge and state of discharge. Besides, the ADC also had been calibrated by providing the graph of the mean value of the voltage through the potentiometer that will make easier for the user to know the value of the voltage when refereeing to the ADC value. For future progress of this section will be use ADC process to measure the value from voltage and current sensors that will be sent the value of voltage and current to make main controller to be able to control the switching state of the system. Besides, this component also will be used to make a data logging during scheduling function by using crontab function from the main controller.

• Charging and discharging process

Currently, this process be used TP4056 charging chip that been using hard switch method which is been using external switch to make interval for charging and discharging process. Besides, LED been used to act as load during discharging process. After that, oscilloscope and multimeter also been used to measure the behaviour of current and voltage curve during discharging and charging process. In the future, this process will be improved by connecting to the main control via ADC chip and the crontab function will take place to do the scheduling charging and discharging function and will use the household demand data base to reduce the demand cost during peak hours.

• Buck converter

For this section, buck converter had already been tested whether able to step down the voltage to the safe level to be connected to the main controller and other components of the system. Shown that, the output voltage been in the suitable voltage to be used in this project which is 3.3V that is suitable to be connected to the input or output pins of the main controller. For future progress, this converter can also be used to control the switching mode SimulationFor this section will be explained about the current progress for simulation part. This section had been used to show on how the state of charge of the battery can be set and to show on how the hybrid system been operated. For future progress, the Kalman filtering function can be implemented in this system to make the simulation able to conduct estimation for the state of health of the battery.

Risk Management

This section will be used to explain about the risk of this project which is there are 2 main risk that been identified by group project which are: -

• Overcharge: -

This condition might be very dangerous when group project did not monitor the exact voltage curve during charging process especially when operating Lithium-ion battery. This is because this condition will allow excess current been through battery that will give a negative affect toward the electrolyte of the battery. This condition also might lead toward the battery will undergo thermal runaway process that will also cause battery burn or swelling.

• Over discharge: -

This condition also will give a major drawback toward the performance of the battery and will give a negative effect toward state of health of the battery. This condition will lead toward the battery will face power fading and lose capacity over time usage. This will make the lifetime of the battery will be reduced. Based on the above risk, there are several ways can be implemented to make isolation method or to prevent those risks which are: -

• Monitored current and voltage curve during charging and discharging process. This step can be done manually or automatically which is the value of voltage can be monitored by main controller by using ADC that will make this system become more reliable to be implemented in the real applications.
• Build a case for the battery to act as safety precaution. This step will help to reduce the momentum of explosion produced by battery.
• Use temperature sensor to help to monitor the operating temperature to ensure the battery did not facing thermal runaway condition that will give a negative effect toward the state of health of the battery.
• Make a proper Battery Management System that will give an efficient process toward the battery such as battery balancing function that will ensure all the battery having the same rate of charge and discharge.

Conclusion

Ageing effect can be improved by: -

• Provide good switching mode
• Regulate a proper operating temperature
• Make a proper battery management system (BMS)

References

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