Project 2 Thermal modeling of battery pack

1.10 cell series lithium ion battery model, simulate the thermal effects and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB.

2.Objective

To analyze temperature and life cycle parameters of the 10 cell series battery pack.

• Connect 10 cells in series analyze the response to a cyclic charge and discharge source.
• Change the ambient temperatures of the battery pack and compare the performances.
• Add the fading parameters of the battery and analyse the performance after each charge/discharge cycles.

3.Simulink Modelling of Battery pack

3.1 Need of Battery Modelling

An accurate forecast of the remaining driving range of an electric vehicle (EV) is crucial to avoid range anxiety. Drivers need to know how much further they would travel before their vehicle batteries require a recharge. In addition, the battery management system should predict when batteries need replacement. The remaining charge calculation must be precise to utilize the battery’s full capability. The state of charge (SOC) of a battery or pack of batteries is analogous to a fuel gauge of a conventional vehicle.

3.2 Battery Modelling

The Battery modeling procedure followed in the MATLAB is explained below. The MATLAB model is available from the library given below.

Battery (Table-Based)

Library:

Simscape / Electrical / Sources

The Battery (Table-Based) block represents a high-fidelity battery model. The block calculates no-load voltage as a function of charge level and optional temperature using lookup tables and includes several modeling options:

• Self-discharge
• Battery fade
• Charge dynamics

The Battery (Table-Based) block has four modeling variants, accessible by right-clicking the block in your block diagram and then selecting the appropriate option from the context menu, under Simscape > Block choices:

• Uninstrumented | No thermal port — Basic model that does not output battery charge level and simulates at a fixed temperature. This modeling variant is the default.
• Uninstrumented | Show thermal port — Model with exposed thermal port. This model does not output internal charge level of the battery.
• Instrumented | No thermal port — Model with exposed charge output port. This model uses a fixed temperature throughout the simulation.
• Instrumented | Show thermal port — Model that lets you output internal charge level of the battery. Both the thermal port and the charge output port are exposed.

The instrumented variants have an extra physical signal port that outputs the internal state of charge. Use this functionality to change load behavior as a function of state of charge, without the complexity of building a charge state estimator.

The thermal port variants expose a thermal port, which represents the battery thermal mass.

The battery equivalent circuit is made up of the fundamental battery model, the self-discharge resistance RSD, the charge dynamics model, and the series resistance R0

Simulink model of the Battery Pack was shown below:

Blocks Used in the simscape:

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.

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.

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 SOCThis subsystem takes current as input and gives the battery SOC % as output. A current sensor block is used and connected for soc estimation

After the simulated the block the graph was generated ,which shown below,

Case1: 26.85' C - 300 K

Case 2: 36.85'C - 310 K

4.Conclusion

MATLAB library model parameters were evaluated for its life cycle and thermal effects parameters. A battery pack with 10 cells connected in series also made with a source of charging and discharging cycle.

The thermal effects of battery pack at different ambient temperatures for cycling charging/discharging has been analysed and plotted. The life cycle performance also evaluated for individual cells and overall battery pack.