Project 2 Thermal modeling of battery pack

Ans)

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 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.

circuit construction and working :

* in this ckt we use li-ion cell 1 to 10 , temperature sensors ,ambient temp block , state of charge estimation scope, charge discharge profile given to ckt ,from & goto block block matlab simulink

* Cell 01 to O4 Subsystem :

* 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 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 = T_A – T_B.

* 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 :

* This block models heat transfer in a thermal network by convection due to fluid motion. The rate of heat transfer is proportional to the temperature difference, heat transfer coefficient, and surface area in contact with the fluid.

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