Project 2 Thermal modeling of battery pack
PROJECT 2 THERMAL MODELING OF BATTERY PACK
The temperature of the Lithium Ion battery cells important for its performance , efficiency , safety and capacity and is influenced by the environmental temperature and by the charging and discharging process itself. Battery management system BMS take into account this effect as the temperature at the battery cell is difficult to measure often the tempertaure is measured on a nearby by the poles of the cell although the accuracy of predecting the cell temperature with those quantities is limited .Therefore a thermal model of the battery i sused in order to calculate and estimate the cell temperature.
This project uses a simple representation for the thermal model and shows how the thermal parameters are identified using input output measuremnts only. where the load current of the battery represents the input while the temperature at the poles represent the output of themeasurement with a single measurement the eight model parameter can be determined using the method of at least square .Experimental results show that the simple model with the identified parameters fits very accurately to the measurements.
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.
- Lithium Ion Battery pack with a fault is to simulate a battery consisting of the multiple series connected cells in an efficient manner it also show 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 modules in series. Instead asingle cell is used and the terminal voltage is scaled up by the number cells
- The fault is represented by changing the parameters for the cell 5 fault subsystem reducing both capacity and open circuit voltage and increasing the resistance values.
Battery Pack
Cell 1 to 4
- Cell subsystem basically consists of a thermal model and lithium cells 1Rc block which calculates the temperature and thermal effect of the battery pack.
- The block which are inside the cell subsystem in PS gain block which is multiples the input physical signal by a constant .Other blocks are the voltage sensor and controlled voltage source.
- The voltage sensor block represents an ideal voltage sensor that converts voltage meaasured between any electrical connections into a physical signal proportional o the voltage .
- A controlled voltage source represents an ideal voltage source that is powerful enough to maintain the specified voltage at as output regardless of the current passing through it .The output voltage is V-Vs where Vs is the numerical value presented at the physical signal port.
Thermal Model
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- Thermal Reference This block represented a reference point in a thermal network is equal to absolute zero.
- Controlled Heat Flow Rate Source This block represents an ideal energy source ina thermal network that can maintain a controlled heat flow rate regardless of the temperature difference .The heat flow rate is set by the flows from port A and Port B
- Thermal Mass This block model internal energy storage in thermal network .The rate of temperature increase is proportional to the heat flow rate into th ematerial and inversely proprtional to the mass and specific heat of the material
- Temperature Sensor This block measures temperature in a thermal netwrk .There is no heat flow through the sensor. The physical signal port T reports the temperature diffrence across the sensor. The measurement is positive when the temperature at port A is greater than the temperature at port B
Lithium cell 1RC Subsystem
- This block basically consists of the 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
- Resistance value table which is depends on an external physical inputs SOC and T
- Voltage value which implements the cell main branch voltage source and determines values for capacity and state of charge .
Thermal Behaviour and fault setup
Lithium Ion cell one Rc branch equivalent circuit detail fo 10 cells
AC current source
The peak amplitude was a set to 50A fro cyclic charge and discharge
Temperature source
Used this block for ambient temperature and ambient tempertaure T_int is set as 293 K
Convective Heat Transfer
The heat transfer in a thermal network by convection due to fluid motion.The rate of the heat transfer is proportional to the temperature diffrence heat transfer coefficient and surface area wit the fluid.
SOC Estimation
- SOC calculation here we used gain block intergrator sum block with Ps simulink converter
- The model estimates the battery SOC using the counting method .The intial SOC of the battery is assumed to be 100%
- This subsystem takes current as input and gives the battery SOC as output A current sensor block is used to measure discharge current and connected to SOC estimation.
TEST Ambient temperature (K) Cell Tempertaure (K) (1-4) Cell Tempertaure (K) (5) Cell Tempertaure (K) (6-10)
1 293 293 293 293
2 293 299 293 299
3 293 310 320 310
Test 1
TEST Ambient temperature (K) Cell Tempertaure (K) (1-4) Cell Tempertaure (K) (5) Cell Tempertaure (K) (6-10)
1 293 293 293 293
Cell Temperature
We can see that there is much fluctutation in cell 5 due to fault.
SOC
We see that the battery is fluctating every 301 200 seconds which depends upon the thermal behaviour of the battery pack.
CONDUCTION
Cell 4-5 Cell 5-6
Conduction is basically here heat flow rate and temperature difference vs time.
CONVECTION
Cell 1-4 Cell 5 Cell 6-10
The above graph highlights the heat flow rate and temperature difference by the convection medium.
CYCLIC CHARGE/ DISCHARGE
Charge and Discharge are depending upon current and voltage vs Time .This cyclic charge and discharge were calculated at 50A peak amplitude.
TEST 2
TEST Ambient temperature (K) Cell Tempertaure (K) (1-4) Cell Tempertaure (K) (5) Cell Tempertaure (K) (6-10)
2 293 299 293 299
Cell Temperature
We can see that in cell 5 temperatuure rise to 310k and it goes fluctuating from 317k to 330k and end at 334k
SOC
We see that the battery is fluctuating every 301 200 seocnds which depends upon the thermal behaviour of the battery pack.
CONDUCTION
Cell 4-5 Cell 5-6
Conduction is basically here heat flow rate and temperature difference vs Time
CONVECTION
Cell 1-4 Cell 5 Cell 6-10
The above graph shows the heat flow rate and temperature by convection medium
Cyclic Charge /Discharge
Charge and discharge profiles are depending upon current and voltage vs Time
TEST Ambient temperature (K) Cell Tempertaure (K) (1-4) Cell Tempertaure (K) (5) Cell Tempertaure (K) (6-10)
3 293 310 320 310
Cell Tempearture
We can see that in cell 5 the temperature rise to 325k and goes fluctuation from 327k to 331k and end at 334k
SOC
We can see that the battery is fluctuating every 301 200 seconds upon the thermal behaviour of the battery pack
CONDUCTION
Cell 4-5 Cell 5-6
Conduction is basically here heat flow rate and temperature differnce vs time.
CONVECTION
Cell 1-4 Cell 5 Cell 6-10
The above graph highlights the heat flow rate and temperature differnce by convection medium
Cyclic charge /discharge
Charge and discharge profiles are depending upon current and voltage vs Time . teh cycle charge and discharge are calculated at 50A peak amplitude.