Project 2 Thermal modeling of battery pack

Aim : To study the lithium ion battery pack with theire temperature effect and its effect on life cycle as well as performance.

Objective :

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:

now a days lithium ion battery are mostly used in electric vehicles we must know its charge and discharge rates to operate this battery’s in efficient manner and without damage when this battery’s in operation this temperature of it must be kept in limit we simulate the thermal effect of this cell , by knowing the how much temp rise take place we can provide efficient cooling to the battery’s so that the life cycle of the battery increases we will see a model on this issue below and explanation as follows

cells connected in series and one of the cells is faulty so what will be thermal effect . 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.

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 mat lab Simulink

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 Source block represents an ideal source of thermal energy that is powerful enough to maintain specified temperature at its outlet regardless of the heat flow consumed by the system.

The source generates constant absolute temperature, defined by the Temperature parameter value.

Temperature Sensor:

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.

The block positive direction is from port A to port B. The measured temperature is determined as

T = TA – TB.

This block represents an ideal energy source in a thermal network that can maintain a constant absolute temperature at the port regardless of the heat flow rate. This block is used for ambient temperature which we can set and check results .

Convective Heat Transfer :

The Convective Heat Transfer block represents a heat transfer by convection between two bodies by means of fluid motion. The transfer is governed by the Newton law of cooling and is described with the following equation:

where

Q Heat flow
k Convection heat transfer coefficient
A Surface area
TA,TB Temperatures of the bodies
Connections A and B are thermal conserving ports associated with the points between which the heat transfer by convection takes place. The block positive direction is from port A to port B. This means that the heat flow is positive if it flows from A to B. this used for 1-4 cells and 6-10 cell.

from and goto 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. From and Goto blocks allow you to pass a signal from one block to another without actually connecting them.

state of charge 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 ckt 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. results at 300 k ie 26.85°C

2. results at 310 k ie 36.85°C

3. results at 324 k ie 50.85°C

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

1-4 cells are normal cell 5 th cell is faulty 6-10 cell is normal cell as we are simulating thermal effect on we give Cyclic Charge/ Discharge Profile to circuit the waveform you can see above results all conditions it is same but when ckt is run on this drive cycle profile as 5th cell was faulty it will show temperature rise high than any other cell and the life cycle of cell get reduced and cell even can get damage

so as we give temp of results at 300 k ie 26.85°C the 1-4 and 6-10 cell temp is near to 316k

but 5th faulty cell temp goes to 330k ie 56.85°C and the drive cycle is shown which is Cyclic Charge/ Discharge drive cycle

in condition two we give temp 310 k ie 36.85°C and 1-4 and 6-10 cell temp is near to 326 k but 5th faulty cell temp goes to 340k ie 66.85°C and the drive cycle is shown which is Cyclic Charge/ Discharge drive cycle

in condition two we give temp 324 k ie 50.85°C and 1-4 and 6-10 cell temp is near to 340 k but 5th faulty cell temp goes to 354k ie 80.85°C and the drive cycle is shown which is Cyclic Charge/ Discharge drive cycle

conclusion :

we simulated the thermal effect and compared at various temperature ,faulty cell temp rise more than normal cell charge and discharge cycle given and due to temp rise it can damage the cell and reduce the performance of the battery.