Project

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.

Nominal Voltage= 3.6V

Max. Voltage= 4.2V

Nominal cell capacity= 3500mAh = 3.5 Ah

Rated power=150kw

Rated voltage=120v

Design for cells in Series

Number of cells in series = total voltage /cell nominal voltage

Assuming the max voltage as the total voltage

Number of cells in series = 120 /3.6

Number of cells in series = 33.33

Rounding off the number of cells in series depends on minimum and maximum voltages

Rounding Off assumption 1 (Rounding off 33.33 to 33)

Nominal battery voltage = 3.6 * 33 = 118.8V

Maximum battery voltage = 4.2*33 = 138.6 v

Minimum battery voltage = 2.7 *33 =89.1V

Rounding Off assumption 1 (Rounding off 33.33 to 34)

Nominal battery voltage = 3.6 * 34 = 122.4V

Maximum battery voltage = 4.2*34 = 142.8v

Minimum battery voltage = 2.7 *34=91.8V

This Rounding off Assumption 1 (Series cells of 33 numbers) works out within the required range

Design for cells in parallel

Number of cells in parallel = Total current/cell nominal capacity

First finding the motor current= (rated power *1000)/rated voltage = (150*1000)/120 =1250A

Number of cells in parallel = 1250/3.5

Number of cells in parallel = 357.14

Rounding it , the number of cells in parallel is 357

Thus the rquired battery pack configuration is 33s357p

b.Draw the BMS topology for this battery pack.

For the above battery pack the cells are more than 18 so we use master & slave topology

In this topology, we use daisy chain interface. There are 2 slaves here and both the slaves are connected to MCU (Micro controller unit). Slave 1 data is sent to Slave 2 and slave 2 sends the data of both slave 1 and slave 2 to MCU

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

Total number of cells in battery pack = no.of cells in series * no.of cells in parallel

= 3*2

=6 cells

The battery pack model (simscape model with series and parallel connections) is attached and desinged with the following considerations

nominal voltage of cell = 3.6v

Rated capacity of cell =3.5Ah

Maximum voltage of cell =4.2v

Total number of cells in a battery pack = no.of cells in series * no.of cells in parallel

= 3*2 = 6 cells

Nominal voltage of the battery pack = no.of cells in series * nominal volatege of a cell

Nominal voltage of the battery pack = 3*3.6v = 10.8v

Rated capacity of battery pack = no.of cells in parallel * Rated capacity of a cell

= 2*3.5

Rated capacity of battery pack=7Ah

Overall voltage of the battery pack=maximum capacity of the cell*no.of cells in series

=4.2*3

Overall voltage of the battery pack =12.6v

The SOC, voltage, current plots are also attached