Project 2 Thermal modeling of battery pack

EV LIVE BATCH:-21

Project 2 Thermal Modeling of Battery Pack

Aim:- To Simulate the Thermal Effect of 10 cell Series Lithium ion battery model & to compare the Life cycle performance at Various temperature,Charge & Discharge rates using simulink.

Required Blocks for creating Simulink Model:-

• Battery(Table-Based)
• Controlled Current Source
• From Workspace
• Controlled Temperature Source
• Convective Heat Transfer
• Constant block
• Thermal Reference
• Electrical Reference
• Solver Configuration Block
• PS-Simulink converter
• Simulink-PS converter
• Add block
• Scope
• Subsystem block
• Connection Port (PMC_Port)

Model Description:-

• Actually, we have to take 10 Lithium ion cells & then connect them in series i.e:- +ve terinal of 1st cell should connect with -ve terminal of 2nd cell & so on as follows:-

• To reduce the complexity of the model, we will divide this connections into 2 sets of 5 cells in series & place then in separate subsystems.
• Take Controlled temperature source, & connect the S terminal with a constant block through Simulink-PS converter block whose input signal unit is set as "K" (kelvin).

• Now connect the B terminal of Controlled current source with A terminal of Convective Heat Transfer Block & connect the Thermal Reference with the A teminal of Controlled Temperature Source.

• Take a subsystem & named it as "Subsystem 1", then open that subsystem & connect 5 Cells (Table-Based Battery) in series.
• Then Right click on a battery & go to Simscape ---> Block Choices ---> Instrumented | Show Thermal port.
• Then the battery will consist of 4 ports such as +ve,-ve,SOC & H terminal for Thermal conuctor.

• We have to do the same thing with all 5 batteries.
• Then Take three PCM_Ports & change the locations of 2 ports as Left which means that these two will be the inputs for the subsystem & change the location of 3rd PCM_Port as Right which will represent the Output of Subsustem.
• 1st input for the subsystem will be "Battery-1 (+ve)" which represents the +ve terminal of 1st battery & the 2nd Input will be "Thernal Port" which will carry the Heat from the Covective Heat Transfer block.
• Output for this subsystem will be "Battery-5 (-ve)" which represents the -ve terminal of the 5th battery.
• Then connect SOC of every battery with PS-Simulink Converter & then take a add block & connect output from 6 PS-Simulink converter block with Add block which will give the resultant SOC of 5 batteries in series.
• then the Output from the Add block has to be connected with a Outport.

• In the same way we have to create another subsystem which consists of anothe 5 cells in series (From 6th battery to 10th battery) & is named as "Subsystem 2".

• Now connect the Battery-5 (-ve) with Battery-6 (+ve) so that total 10 batteries are connected in series now & forms a complete Battery Pack with 10 cells in series.
• Now call the UDDS current profile into the Base Workspace. UDDS current profile is nothing but it is a drive cycle data in the form of Current vs time.where Charging & discharging of battery take place in different times.
• In order to do that, we have to double click on the "UDDS current profile.xlsx" which is a Excel file.

• then select Coulumb A & B, chage the Output type as Numeric matrix.

• Then click on Import selection. now the UDDS current profile has stored sucessfully in the base workspace.

• Now take From Workspace block & give the data as UDDScurrentprofile which should match the name with the file stored in the base workspace.

• connect it with S terminal of Controlled Current Source.
• Then connect the +ve terminal of Controlled current source with The -ve terminal of battery pack [i.e:- Battery-10 (-ve)]
• Connect the -ve terminal of Controlled Current Source with the +ve terinal of Battery Pack [i.e:- Battery-1 (+ve)]

• Now connect the B terminal with the Thermal Ports of both Subsystems.
• Then connect SOC 1 & SOC 2 with another Add block whose output will give the summation of SOC of 10 cells in series.
• Then connect the scope with the Output from the Add block. & with the UDDS current profile also.
• Then connect a Electrical Reference & Solver configuration block with -ve terminal of battery pack.

• Now the Model is ready to simulate.

Results:-

(A) At Room Temperature of 298.15 K (25 degree celsius):-

• Here we have taken temperature of 298.15 Kelvin or 25 degree celcius & then run the model for 500sec.

• Here we can see that, there are various stages in the UDDS current Profile grapgh such that when the current value is 0 then the vehicle is at standby mode, at that time SOC value neither decreases mor increases. i.e:- SOC remains constant.
• when the current value increases or current value is +ve then the vehicle is in driving mode, at that time battery pack discharges so SOC value decreases during driving mode.
• When the current value decreases or -ve value then the vehicle is said to be in regenerative braking mode condition, at that time battery pack is in charging mode. so SOC value increases during charging mode i.e:- during the -ve current value.
• Initially the SOC of battery pack is at 100%.
• after 500sec,at room temperature of 298.15K under various Charge & discharge cycles, 97.2% of SOC is remaining in the battery pack.
• so we can say that at 298.15 K of temperature, 10 cell series battery pack has 2.8% loss in the SOC.

(B) At 35 degree celsius or 308.15K Temperature:-

• Here we have increased the temperature from 25 degree celsius to 35 degree celcius.
• Then, initially the SOC of the battery pack was 100%
• Then after 500sec, at 35 308.15 K temperature under various charge & discharge cycles, SOC of the battery pack reaches at 96.8%.
• so we can say that there is 3.2% loss in SOC of the battery pack at 35 degree celsius.

(C) At 45 Degree celsius or 318.15 K temperature:-

• Here we have again increased the temperature for the battery pack from 35 degree celsius to 45 degree celsius.
• intially the SOC of battery pack was 100%.
• after 500sec, at 45 degree celcius or 318.15 K temperature under various charge & discharge cycles, SOC of battery pack reaches at 96.6%.
• so there will be 3.4% loss in SOC of battery pack at 45 degree celsius.

(D) At 55 Degree celsius or 328.15 K temperature:-

• Here we have increased the temperature for the battery pack from 45 degree celsius to 55 degree celsius.
• Initially,SOC of the battery pack was 100%.
• then after 500sec,at 328.15 K temperature under various Charge & discharge cycles, the SOC of battery pack has reached at 96.4%.
• So there is 3.6% loss in SOC of 10 cell series Battery pack at 55 degree celsius.

(E) At 65 Degree Celsius or 338.15 K Temperature:-

• Here we have again increased the temperature for battery pack from 55 degree celsius to 65 degree celsius.
• Intially, SOC of the battery pack was 100%.
• Then after 500sec, at 65 degree celsius temperature under various charge & discharge cycle, SOC of battery pach has reached at 96.1%.
• so there is 3.9% loss in SOC of battery pack at 65 degree celsius.

Tabulation:-

• Here we have prepared a tabulation for Change in SOC of battery pack at various temperature under variuos charge & discharge cycles.

Simulation time (Sec)	Temperature (Degree Celsius)	Initial SOC of Battery Pack (%)	Final SOC of Battery Pack (%)	Loss in SOC (%)
500	25	100	97.2	2.8
500	35	100	96.8	3.2
500	45	100	96.6	3.4
500	55	100	96.4	3.6
500	65	100	96.1	3.9

Conclusion:-

• We have sucessfully created a simulink model for 10 Lithium ion cells in series to check the performance of battery pack under various temperature & various charge & discharge cycles.
• We changed the temperature as 298.15K,308.15K,318.15K,328.15K & 338.15K repectively.
• We have used UDDS current profile for different charge & discharge cycles.
• from the result scopes & tabulation, we can conclude that for 500sec simulation of the model, SOC of battery pack decreases slowly by increasingh the temperature.
• but if we increase the simultion time, then theSOC of the battery will varry more at various temperature.
• But the conclusion is, by increasing the temperature, SOC of 10 cells series battery pack decreases.