Project 2 Thermal modeling of battery pack

PROJECT 2 THERMAL MODELLING OF BATTERY PACK

Question:

For a 10-cell series lithium-ion battery model, simulate the thermal effects and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB.

Theory:

These days, lithium-ion batteries are primarily used in electric vehicles. As such, it is important to understand the charge and discharge rates of these batteries in order to operate them effectively and without damage. Additionally, we must simulate the thermal effect of these batteries by determining how much of a temperature rise occurs. This will allow us to effectively cool the batteries and extend their lifespan. Below is a model that illustrates this problem and provides an explanation.

This is inbuilt model in MATLAB environment to illustrate the Thermal effects of a battery pack using a fault method.

This example shows how to simulate a battery pack consisting of multiple series-connected cells in an efficient manner. It also shows how a fault can be introduced into one of the cells to see the impact on battery performance and cell temperatures. For efficiency, identical series-connected cells are not just simply modelled by connecting cell models in series. Instead, a single cell is used, and the terminal voltage scaled up by the number of cells. The fault is represented by changing the parameters for the Cell 10 Fault subsystem, reducing both capacity and open-circuit voltage, and increasing the resistance values.

Model

Circuit construction and working -

in this circuit we use li-ion cell 1 to 10, temperature sensors, ambient temp block, state of charge estimation scope, charge discharge profile given to circuit, from & go to block block MATLAB Simulink

Cell 01 to O4 Subsystem:

Cell subsystem basically consist of a Thermal Model and Lithium Cell 1RC block which calculate the temperature and thermal effect for cells and overall calculate for the battery pack.

This block basically consists of capacitance value © table which depends on an external physical signal inputs SOC and T. It is assumed that the capacitance value is slowly varying with time, and hence the equation I = C*dv/dt holds.

Resistance value (R) table which depends on an external physical signal inputs SOC and T.

Voltage value (EM) which implements the cell's main branch voltage source, and determines values for capacity (C) and state of charge (SOC). The
defining equations depend on cell temperature, T.

output of one cell is connected with the SOC estimation whereas other output is connected with AC current source for cyclic charge/discharge profile.
The peak amplitudes set to 50 A for cyclic charge and discharge. A basic parameter of AC current source is as

other block which are used in lithium-ion battery pack are as:

Temperature Source:

The Temperature Sensor block represents an ideal temperature sensor, that is, a device that determines the temperature differential measured between two points without drawing any heat.

Connections A and B are thermal conserving ports that connect to the two points where temperature is being monitored. Port T is a physical signal port that outputs the temperature differential value. This block is used for ambient temperature which we can set and check results.

Convective Heat Transfer:

This block models heat transfer in a thermal network by convection due to fluid motion. The rate of heat transfer is proportional to the temperature difference, heat transfer coefficient, and surface area in contact with the fluid.

this used for 1-4 cells and 6-10 cell

From and go to blocks

The Goto block passes its input to its corresponding from blocks. The input can be a real- or complex-valued signal or vector of any data type. From and Goto blocks allow you to pass a signal from one block to another without actually connecting them.

The From block accepts a signal from a corresponding Goto block, then passes it as output. The data type of the output is the same as that of the input from the Goto block.

SOC estimation

The Coulomb counting method measures the discharging current of a battery and integrates the discharging current over time in order to estimate SOC

This subsystem takes current as input and gives the battery SOC % as output. A current sensor block is used and connected for soc estimation

This circuit estimates the battery SOC % using coulomb counting method. It takes current as the input and gives SOC% as output. Initial SOC of the battery is assumed to be 100% (1)

example shows how to simulate a battery pack consisting of multiple series-connected cells in an efficient manner. It also shows how a fault can be introduced into one of the cells to see the impact on battery performance and cell temperatures

Results:

1) At 293.15K

Cell temperature is at 16.85°C (310K – 293.15K) and faulty cell is at 31.85°C

2) At 310K,

Cell temperature is at 31.85°C (325K-293.15K) and faulty cell is at 46.85°C

3) At 330K,

Cell temperature is at 52.85°C (346K-293.15K) and faulty cell is at 66.85°C

Charging And Discharging rates

Current rate

Voltage rate

Conclusion

We compared and replicated the thermal effect at different temperatures. When a defective cell's temperature rises over the typical cycle of charge and discharge, the cell may be damaged and its performance may be diminished.