Project 1

Q1. 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.

Ans-

given data,

cell nominal capacity= 3500 mAh

power = 150 Kw

Rated motor voltage= 120

Nominal cell voltage = 3.6

to findout battery pack configuration,

1) for series cell= Rated motor voltage / nominal cell voltage

= 120 / 3.6

no of cells in series = 33.33 .

2) For parallel cell = Motor current / cell nominal capacity

Power = voltage * current

current = 150 / 120

current = 1.25 A

Parallel cells = 1.25 / 3.5

Parallel cells = 0.35

b. Draw the BMS topology for this battery pack.

ans-

for designing topologies we have to considered only no of series cells.here master slave topology used because of it can use more than 18 cells.

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

ans-

here, we have 3 cells should be connected in series and 2 cells should be connected in parallel.

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

= 3 * 2 = 6 cells

For parallel connection, batteries are connected from terminals to same terminals of other batteries that is positive terminal (+) of one battery is connected with positive (+) terminal of other battery and negative terminal (-) of one battery with negative terminal (-) of other Batteries.

For series connection connected from terminal to terminal in a way that the positive (+) terminal of one battery is connected with the negative (-) terminal of the other battery and negative terminal (-) of one battery is connected with the positive terminal (+) of the other battery.

.

The voltage measurement block is connected across the battery pack to measure the battery pack voltage. The scope output used for the battery pack consists of SOC (State of Charge), Current and voltage. The controlled current signal is given as the load to the battery pack. The constant block is determined with battery capacity and it is given to the controlled current block.

1) No of cells in series = Rated motor voltage / nominal cell voltage

= 120 / 3.6

no of cells in series = 33.33 .

2) No of cells in parallel = Motor current / cell nominal capacity

Parallel cells = 1.25 / 3.5

Parallel cells = 0.35

OUTPUT-

Here shows the overall output voltage of the battery pack.

• Plot 1: The SOC (state of charge) is started to reduce from 100% to 50% corresponding to the load given.
• Plot 2: The current signal is determined by the load and the decrease in current is due to regenerative braking.
• Plot 3: The voltage is around 8.3V. The increasing and decreasing voltage is with respect to the regenerative braking.