Project 2 Thermal modeling of battery pack

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.

Solution..,

Objective: For a 10 cells series lithium ion battery model simulate the thermal effects and compare life cycle performance art various temperatures charge and discharge rates using Matlavb

Theory:

Now a days lithium ion battery are mostly used in electric vehicles mus know its charge and discharge rated to operate this battery in efficient manner and with out damage when this battery rated to operate this battery in efficient manner and without daage when this battery is 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 so that the life cycle of the battery increases we will see a model on this issue below and explanation as folllows

Cells connected in series and one of the cell is faulty so what wll be thermal effect This example shows how to simulate battery pack consisting of multiple series connected cell 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 temperature For efficiency identical series connected cells are not just simply modeled by connecting cell models in series Instead a single cells 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 ckt voltage and increasing the resistance values

As we can see in the model the 20 lithium ion cells are connected in series

the 10th cell in the battery pack is considered as faulty.

The fault is represented by changing the parameters for theCell 10 reducing both capacity and open ckt voltage and increasing the resistance values

now if we open the cell 01 to 09 block

we can see that the cells is working at its full potential

Now if we open the cell 10 block

We can see that

1) capacity is multiplied by 0.95

thus mean that capacity is reduced by 5%

2) The open ckt voltage is multiplied by 0.9

this means that the open ckt voltage is reduced by 10%

3) The cell resistance is multiplied by 5

this means that cell resistance is increased 5 times

as resistance increases the temp of cell also increases

this all chiange are done to show that cell 10 is in faulty condition

From the model

there is convective heat transfer from battry pack to surrounding environment and there if conduction heat transfer between the cells of battery pack

It is mentioned that 10 cell series lithium ion battery thus we have to make certain changes in the model.

thus change 9 cells to 4 cells

Change 10th cell as 5th cell and let this cell be faulty

Change 10 cell to 5 Cell

thus we got in total 10 lithium ion cell and 5th cell is faulty

To estimate SOC:

To Measure the temperature of cells:

1) Create Subsytem:

here in the subsytem we have used a temperature sensor block

Where A point is connected to temperature port and B point is connected to thermal reference

the T port if temperature sensor block is given to ps- simulink converter and then output of ps simulink converter is given to goto block

the 3 different from block is then used in the model of respective goto blocks

and this 3 from blocks are connected to 3 input max and output of max is connected to scope

To measure the ambient temperature:

A temperature sensor block is taken

A port is connected to ambient temp

B port is connected to thermal reference

and T port is connected to Ps simulink block

and the output of Ps simulink block is given to scope

The complete model looks like

from the parameters we can see that

the peak amplitude of the ac current source is 50 Amp

and we have considred phase shift as 0

and frequency is considred as 1/600 Hz

here in this model

the load is considred in the form of alternating current which is provided by the ac current source block

Ac current source positive termiank is connected to the battery pack and the negative terminal is connected to the electrical refference

Simulation Results"

Run simulation for 7200 Seconds

1) The ambient temp is found to be 293.1K

2) Temperature of Cells:

Thuf from simulation results we can found that the faulty cell have higher temp than the normal cells

the normal cell temp is between 295K to 325 K

3) State of Charge (SOC)

We found that the SOC graph is fluctuating in the entire 7200 Seconds time period the soc rises from o to 0.95 in 0 to 318 seconds and then fall from 0.95 to 0 in 318 seconds to 600 seconds

from the plot we found hat there are 6 charging discharging cycles in 3600 Hours thus we can say that the life cycle of battery pack is 6 cycles per hour

This life cycle can be increased if we remove the faulty cell.

COnclusion:

Thus we found that if the faulty cell is there in the battery pack, the life cycle of battery pack reduces

If the temperature  of the faulty cell is much higher than normal working cells and because of this high temperature the efficiency of battery pack gets reduced.