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.
The 10 cell series lithium ion battery model.
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.
Thermal Effect :
At 10 celll we are connected a temperature sensor .we are calculatin the ambirnt temperatue is giving to the A of temperature sensor ,b is connected to the thermal reference ,bcoz we do not have any temperature from other side.
It is a simple first order thermal model for a single cell which assumes a thermal mass with even electrolyte temperature through out the resitive loss within the cell contribute to the heating of this thermal mass connected to this model would also be a thermal source for the convective and radient thermal energy due to environment .in this some of the resistive losses and fed those heat flow to the bttery thermal mass then the measured temperature is fed back to the circuit elements .
Eqivalent Circuit Model :
EM = open circuit voltage
RO= Thermal resistance
C,R,I =Transient Dynamics
Here ro is the voltagae drop once a load is connected .
RC brances are the time response and frequency response .
all these elements are non linear.
Equivalent Model for 1 RC branch :
Circuit elements depends on soc and temperature .we can create lokup table for those values.
The Full drive cycle :
Results :
From the temperature results ,we can see that the threeBattery packs all start out with the same initial temperature of 303k,whicjh as the ambient temperature .After t=23 sec the temperature of the second packbegins to rise noticeably compared to second packs.After t= 190 sec the tempwrature of the second pack rises rapldy.Betwee t=125 and 163 sec the temperature of teh second pack decreases slightly from 304 to 303.9k whereasthe temperature of the other two packs remains cosatantat 303.3k .this corresponds to the period in the drive cyccle where the vehicle is rest.At t=190sec ,the vehicle acclerates rapidly and this is reflected increases in the second pack temperature.The temperature of the other two packs also increases quicker but to a lesser extennnt than the second pack at the same time period .
At t=461 sec the second pack reaches atemperature of 309k where as that of the other two packs is still 304k .After t=500 sec thetemperature of the first and third pack of diverge slowly from each other but continue their general increasing trend with the first pack havin a higher temperaurue throughout .However the second pack temperature follows a general decreasing trend .At t=1354 sec the vehicle begins to seclerate and returns to rest att=1367 till t=1987 sec .during this same period ,the second pack temperature dramatically decrease from 307k to 305k.The temperature of the other two packs also decrease /the temperature of the first pack drops from 305.5k to 05k and that ofthe that third pack from 305k to 304k.After this the vehicle start to acclerate ,that reflected to temperature of pack increasing.At t=2433 maximum peak attains the temperature .
The cyclic charge and discharge :
Results :
The temperature of the first three packs increases in a flucating manner due to the cyclic nature of the charging and discharging load .After t=500 sec the temperature profiles of the first and third pack diverges.At t=1000 sec ,the temperature of the second pack had reached 357.4k ,first and third pack 326k and 325k respectively.At t=2000k the temperature of the second pack to 387.3k .first and thirsd pack 345.1k and 342k.At t=5000 sec pack levelled of.
The DC CURRENT :
Results:
