Project 1

1. Design a battery pack for a car roughly 150 Kw with 120 V. Use 3500 mAh 3.6V nominal NMC chemistry cell.

a. Design the battery pack configuration.

Given That,

Cell Nominal Voltage = 3.6V

Cell capacity = 3500mAh = 3.5Ah

Motor Rating = 150kW

There for, Motor Continuous current = (150*1000)/120 = 1250 Amps

Motor Nominal Voltage, Vnom = 120V

No of cells in series:-

No of cells in series = Rated Motor Voltage / Nominal Cell Voltage

= 120/3.6

= 33.33 Nos

No Of Cells in Series Total Voltage

Case - I 33 33 * 3.6 = 118.8 V

Case - II 34 34 * 3.6 = 122.4 V

The Rated voltage for Motor is 120V. So we select the Case - II. No of Cells in Series = 34

No of cells in Parallel:-

No of cells in Parallel = Motor Continuous Current / Cell Nominal Capacity

= 1250 / 3.5

= 357.14 Nos

No Of Cells in Parallel Total Voltage Discharge Current C-Rate

Case - I 357 357 * 3.5 = 1249.5 A 1250 / 357 = 3.501 3.501 / 3.5 = 1.002

Case - II 358 358 * 3.5 = 1253.0 A 1250 / 358 = 3.491 3.497 / 3.5 = 0.997

it is always better to discharge the cells at nearest & lower 1C rate. According to this, both are near 1C but still one is

smaller and as we can see the C-rate is lower in the case of Rounding up we will chose that. So we select Case - II.

No of cells in Parallel = 358

So the configuration of the Battery Pack will be 34S358P

b. BMS Topology of the above configuration.

The Total number of cells = 34 * 358 = 12,172.

Since the number of series cells exceeds 18 Cells, We using Master - Slave BMS topology for battery pack construction.

So the BMS topology consist of 4 Slave modules and 1 MCU. Cells can be divided in such a manner that each module contains

17 Cells in Series and 179 Cells in Parallel.

2. Build a 3S2P battery pack configuration with generic battery block using Matlab/Simulink.

Nominal voltage of the cell(v) = 7.2V

Fully charged voltage of the cell(V) = 8.3807V

Rated capacity of the cell(Ah) = 5.4Ah

We have total of 3 * 2 = 6 cells in the design a battery pack so the calculation is as follows

Nominal voltage of the battery pack(V) = 7.2V x 3 cells = 21.6Volts

Fully charged voltage of the battery pack(V) = 8.3807V x 3 cells = 25.24volts

Nominal capacity of the battery pack(Ah) = 5.4Ah x 2 = 10.8Ah

The Resulting scope output given below.