Project 2 Thermal modeling of battery pack

1. 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.

A) AIM : To simulate the thermal effects and compare life cycle performance at various temperatures, charge & discharge rates for a 10 cell series lithium ion battery model by using MATLAB SIMULINK.

 THEORY : Now a days lithium ion battery are mostly used in electric vehicles we must know its charge and discharge rates to operate this batterys in efficient manner and with out damage when this batterys 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 batterys so that the life cycle of the battery increases we will see a model on this issue below and explaination as follows

• Cells connected in series and one of the cell 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 modeled 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.

simulink model :

 

so for the 10-cell series lithium-ion battery here used Matlab and Simulink for findings thermal effect and life cycle performances relc to temperature, charge, and discharge and also conduction and convection blocks are used to show how the heat transfer takes pla in battery packs.

Lithium-ion battery pack with fault is to simulate a battery pack consists of multiple cells connected in series efficiently.it also shows how a fault can be introduced into one of the cells to the impact on battery performance and cell temperatures, for efficiency the identice series-connected cells are not just simply model by connecting cell models in series. Instead single cell is used, and the terminal voltage is scaled up by the number of cells. the fault is represented by changing the parameters for the cell 5 subsystem, reducing both the capacity and open-circuit voltage, and increasing the resistance values. 

How the connection is made

If the 10 lithium-ion battery cells are connected in with the combination of three packs the fist consistent 4 cells in series 2nd pack consist of Icell which set to design as fault for study purpose to observe temperature changes within battery pack and the 3rd pack contain b cells in series.

The heat transfer is observed between the packs by conduction and convection block which are modes of heat transfer.

T subsystem is attached in between every pack to plot the temperature graph of the cell of that particular battery pack

Also external ambient temperature source is attached and also thermal sensor is attached to the same. to indicate the value in the display.

This battery pack is connected to AC current source to observe the cyclic charge and discharge rate graph.

Also we added a current sensor in between the battery pack AC current source to calculate the SOC of the battery

The cell temperature and soc graphs are plotted in indicating the temperature of cell no 4, cell no 5, and bell no 10 scope which

All the other results are located in the simscape result menu.

Cell 01 to 04 subsystem :

The cell subsystem basically consists of a thermal model and lithium cell IRC block which calculate the temperature and thermal effect for cells and overall calculate for the battery pack.

The block which are inside the cell subsystems are PS gain block which multiplies the input physical signals by a constant i.e y-u. gain another block are voltage sensor and current-voltage source.

The voltage sensor block represents an ideal voltage sensor, this is a device that converts voltage measured between any electric connection into a physical signal proportional to the voltage.

The current-voltage source represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current passing through it. The output voltage is V=Vs, where Vs is the numeric value represents at the physical signal port.

Thermal model :

This block represents the systems are,

Controlled Heat flow rate source :

Variable source of thermal energy ,characterized by heat flow.

Library :

Simscape/foundation library/Thermal/Thermal sources

Description : The Controlled Heart Flow Ratte Source block represents an ideal source of thermal energy thatt is powerfull enough to maintain specified heat flow at its outlet regardless of the temperature difference across the source.

Connections A and B are thermal conserving ports corresponding to

the source inlet and outlet, respectively. Port S is a physical signal port through which the control signal that drives the source is applied. You can use the entire variety of Simulink signal sources to generate the desired heat flow variation profile. The heat flow through the source is directly proportional to the signal at the control port S.

The block positive direction is from port A to port B. This means that a positive signal at port S generates heat flow in the direction from A to B

Thermal reference : Reference connection for the thermal ports .

Description : The thermal reference block represents a thermal reference point,that is apoint with an absolute zero temperature ,concerning which all the temperature in the system are determined.

Thermal Mass :

Description :The Thermal Mass block represents a thermal mass ,which refleects the ability of a material or a combination of material to store internal energy.The property is characterised by the mass of the materialand its specific heat.The thermal mass is described with the following equation .

Q=c*m dT/dt

 Temperature sensor : Ideal temperature sensor. and it is also known as thermsl sensors.

Description : The Temperature Sensor block represents an ideal temperature sensor, 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 thetwo points where the 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

Lithium Cell 1Rc subsystem :

This block especially consists of the capacitor (C)value table which depends upon an external physical signal input SOC and T.it is assumed that the capacitor value is varying with the time and hence the equation i=C*DV/dt holds.

 Resistance value (R) table depend on external physical signal inputs SOC and T.

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

Thermal Behaviour and fault setup :Lithium ion cell one RC -branch equivalent circuit details for 1 to 10 cells.

No of connected in series are 4

Intial temperature -299.1k

For cell 5 cells(fault setup) in this cell ,I have done changes in the electrical systems of the cell so that we cam see the fault.

No of connected in series =4

Intial temperature = 299.1k

Capacity (A/hr) = Capacity_LUT*0.95

EM-open-circuit voltage (volts) = Em_LUT*0.9

RO terminal resistance (ohms) = RO_LUT*5

R1 cell resistance (ohms) = R1_LUT*5

C1 capacitance (farads) = C1_LUT*0.95

For cell 06 to 10

 No of connected in series = 5

intial temperature =299.1k

PARAMETERS :

Battery configuration:

 

Temperature source :

A constant source of thermal energy,characterised by temperature 

 

Description : The Temperature Source block represents an ideal source of thermal energy that is powerful enough to maintain a specified temperature at its outlett regardless of the heat flow consumed by the system.

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

there used ambient block and set the temperature for 299.1k or 25.95.

 

Thermal elements :

conductive heat transfer

Library- Thermal elements

Description : The Conductive Heat Transfer block represents a heat transfer b conduction between two layers of the same material. The transf governed by the Fourier law and is described with the following equation:

Q=K-AD(TA-TB)

 

Connections A and B are thermal conserving ports associated with material layers. The block positive direction is from port A to port B. Thi means that the heat flow is positive if it flows from A to B. The is done from the 2 sets of blocks one is for cell 04 to 05 and another is used for 05 to 06.

Convective Heat Transfer 

Heat transfer by convection\

Library-Thermal elements

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

Q=K-A (TA-TB)

Connections A and B are thermal conserving ports associated with th points between which the heat transfer by convection takes place. Th 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.

Here I used 3 blocks for convection

for cell 01-04

for cell 05

for cell 06-10

Temperature Sensor

Ideal temperature sensor

Library - Thermal Sensors

Description : The Temperature Sensor block represents an ideal temperature sensor, 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 th two points where the 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

Electrical Elements:

here the output of one cell is connected with the SOC calculation whereas the output is connected to with AC source for the cyclic charge/discharge profile

a) AC Current Source

The ideal sinusoidal current source

 

Descripttion : The AC Current Source block represents an ideal current source that maintains the sinusoidal current through it, independent of the voltage across its terminals.

The output current is defined by the following equation:

I=10-sin(2m-fit+psy)

The peak amplitude is set to 50 A for a cyclic charge and discharge. A basic parameter of AC source is as,

 

The ideal AC source maintains the sinusoidal current through it, independent of the voltage across its terminals. The output current is defined by 1=10*sin(2*pi*f*t+PHI) 10 is the peak amplitude,f is the frequency in Hz, and PHI is the phase shift in radians.

Current Sensor :  

The current sensor in electrical systems

Library - Electrical Sensors

Description : The Current Sensor block represents an ideal current sensor, a device that converts current measured in any electrical branch into a physical signal proportional to the current.

Connections + and - are electrical conserving ports through which the sensor is inserted into the circuit. The connection I am a physical signal port that outputs the measurement result

Electrical Reference

Connection to electrical ground

Library

Electrical elements

Description : The Electrical Reference block represents an electrical ground. Electrical conserving ports of all the blocks that are directly connec to the ground must be connected to an Electrical Reference block.. model with electrical elements must contain at least one Electrical Reference block.

Soc Calculation :

 

For SOC calculation here I used gain block. integrator and sum block sum with PS Simulink converter.

For the study ,we have some observation where we getting results for different cell temperature

here we have set ambient temperature is 299.1k or25c

Battery Pack configuration :

Results :

To check the conduction,convection and charge and discharge rate plot we used the simscape results option.

 

1) For Test-1

 

Graphs:

a)Cell temperature :

All the three the cell having the same temperature at the start which is at 2001 kbut in the beginning few seconds of simulation cell no 5 oscillates with more the cell 4 and 10 because its design with fault and ranging to higher temp then cell 4 and 10.after a time period of around 1300 sec both the cells getting are unfollowing the temperature line which was following the same temperature rate cell no 4 and 10 having approximately 315(cell 04 having quite less temp then cell 10 because of no of the cell ore different) k at the end of the simulation and the cell no 5 achieving the higher temperature of around 328 k.

b) SOC :

The SOC graph following the simulation the sinusoidal waveforms structure and fluctuating after 297 seconds and this waveform acheiving the value of more than 100.06 SOC

Conduction :

Conduction is basically heat flow rate (Q) and temperature difference with respect to time.

For cell 04-05 :

Cell no 04-05 and having a high amplitude of waveforms (for heat flow and temperature difference)which are oscillating at apretty high rate which is starting from zero and dropping in to the negative zone at the end of the simulation.

The heat transfer coefficient is -21.32 w/(m^2k)

Thermal conductivity -10.66 w/m k

For cell 05-06

For cell no 05-06 both the waveforms oscillating at ahigh rate but in a positve zone which are increasing intially and maintaining a certain range.

The heat transfer coefficient is 20.12 w/(m^2k)

Thermal conductivity 10.06 w/mk

d)convection : convection is the process of heat transfer by the bulk of the movement of molecules within fluids such as gasses and liquids.

For cell 01-04 :

For cell no 01-04 the oscillations are pretty low and dropping in to the negative zone at the end of the simulation.the final values for 

The heat transfer coefficient is -71.63 w/(m^2k)

Thermal conductivity -15.76 w/mk

For cell 05 :

For cell no 5 they are starting from0 and falling in to the negative zone the oscillation having high amplitude because of the faulty cell at the end of the simulation.

The heat transfer coefficient is -13.39w/(m^2k)

Thermal conductivity -26.92 w/mk

For cell 06-10 :

For cell no 06 to 10 the falling from zero to the negative zone the oscillation are less at the end of the simulation

The heat transfer coefficient is -82.63 w/(m^2k)

Thermal conductivity -16.36 w/mk

e) charge and Discharge profiles :

In the charge and discharge rate graphb the voltage and current oscillating from pretty highly where current is ranging from -50 to 50A and voltage is ranging from 30 to 43 volts

the final at the end of the simulation for

i(current) = 1.4695e-13A

v(voltage) = 36.33 V 

2)Test 2

a) celll temp :

 

Here the cell no 04 and cell no 10 starting from a temp of 310k at the start of thesimulation and cell no 05 from 299.1k with higher oscillation as compared to the other cells because of the faulty design at the end of the simulation the cells 04 and 10 having the final temp of nearby 315k and cell no 5 acheiving the temperature pf 328k

b)SOC :

 

c)Conduction :

For cell  04-05 :

The heat flow rate plot starts from 20n nand falls in to the negative zone the temperature difference plot starts from 10 and falls in to the negative zone an doscillate at the end of the simulation the final valuye for 

The heat transfer coefficient is -21.32w/(m^2k)

Thermal conductivity -10.66w/mk

For cell 05-06 :

For cell no05-06 theb plot intiate from the negative zone and at the end settle down in the positive zone where the final values for,

d)Convection :

For cell no 01-04 the plots remain the negative zone throughout the simulation with pretty low oscillation with falling nature and the final values at the e d of the simulation

The heat transfer coefiicient is -71.63 w/(m^2k)

Thermal conductivity -15.62 w/mk

For cell 05:

 

For cell no 05  the intial values are 0 and falling in to the negative side with high oscillation because of the fault and the final values are 

The heat transfer coefficient is -13.66 w/(m^2k)

Thermal conductivity -26.28 w/mk

for cell 06-10:

 

For cell 06-10 the plot remains on the negative side,aNnd falling at the end of the simulation

The heat transfer coefficient is -82.64 w/(m^2k)

Thermal conductivity is -16.36 w/mk

e)charge and discharging:

 

charge and discharge rate profilke the plot for current is ranging  in between -50 to 50A and the voltage 30 to 43 volt and the final values for 

I(current) = 1.4695e-13A

v(volt) = 36.33v

3)Test 3

a)cell Temp :

 

The intial temperature for cell no 04 is 310k,the cell no5 is 320k and cell no 10 is 330k,but after some point,cell no 04 and cell no 10 started following the same temperature rate and cell no05 starts oscillating with high values because of fault .The final value for cell no 04 and 10 is arounf 316k and cell no5 is328k because of its fault design

b)SOC:

 

c)conduction :

For cell 04-05 :

For cell 04-05 the plot starts from the negative side and drops and then again increases and maintain through out the simulation of negative zone .The final values at the end of the simulation are

The heat transfer coefficient is -21.32w/(m^2k)

Thermal conductivity is -10.66 w/mk

For 05-06

For cell,no05-06 both the plot starts from the negatuive side and then enetered in to the positive side and the final value at the end of the simulation

The heat transfer coefficient is 20.97w/(m^2k)

Thermal conductivity 10.06 w/mk

d)convection:

for cell 01-04

 

 

For cell no01-04 the final values at the end of the simulation are 

The heat transfer coefficient is -71.64w/(m^2k)

Thermal conductivity -15.y75 w/mk

For cell 06-10

 

For cell no 06-10 the final values at the end of the simulation are

The heat transfer coefficient is -83.30w/(m^2k)

Thermal conductivity -16.34 w/mk

e) Charge and discharge profile :

Charge and discharge rate profile the plot for current is ranging in between -50 to50A and the voltage 30 to43volt and the final values for 

i(current) = 1.4695e-13A

v(volt) = 36.33

Conclusion :

1) As the difference in temperature we can observe the changes inthe heat flow rate by conduction and convection .

2) There are slight changes in cyclic charge and discharge as i fixed peak amplitude at 50A 

3) SOC for all the temperature remain the same so there is no difference inSOC groups.

4) Cell no5 had higher oscillation and we can observe that in every graph because we design that cell for fault.