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.

b. Draw the BMS topology for this battery pack.

Ans:

Aim of the Project:

The aim of the Project is to design a Battery pack of capacity 150Kw, 120V . Develop BMS topology for the battery pack.

Cell specificationused for the battery pack is 3500 mAh 3.6V nominal NMC chemistry cell.

EV design – Battery calculations:

Battery : 150kW, 120V

Current = 150000/120 = 1250Ah

Cell specification: 3500mAh, 3.6V

• In series configuration capacity remains the same and voltage will be the sum of individual cell voltage.
• In parallel configuration, the voltage remains the same and capacity accumulates.

No of cells in series = Nominal voltage of Battery / Cell voltage = 120/3.6 = 33.3 = 33nos.

case 1

Rounding off 33.33 to 33

Nominal battery voltage = Cell nominal voltage *33 = 3.6*33=118.8 V

case 2

Rounding off 33.33 to 34

Nominal battery voltage = Cell nominal voltage *34 = 3.6*34=122.4 V

So, we can pick case 1 which is 33 cells in series

No of cells in parallel = Nominal currentof Battery pack / Nominal current of Cell = 1250/3500*0.001 = 357.14

Rounding of the number of cells in parallel

Number of the cells in parallel = 357.14

case 1 : Battery capacity = 357*3.5 = 1249.5Ah

case 2 : Battery capacity = 358*3.5 =1253Ah

So, choose 1253Ah , no of cells is 358

The battery Pack configaration is 34S358P

BMS Topology:

This is a master and slave topology. Slave 1 is connected to slave 2. Slave 2 is connebted to master controlller. The mastercontroller IS connected to the load through CAN and RS484. Slave 1 and slave 2 is connected to the battery module of17S358P cells.

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

Ans:

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 blockis determined with battery capacity and it is given to the controlled current block.

The parameter given inside the battery is given below:-

• Nominal voltage of a cell 7.2V
• Rated capacity of a cell 5.4Ah
• Maximum voltage of a cell 8.3V

Nominal voltage of the battery pack = no.of cell in series * nominal voltage of a cell
= 3 * 7.2v

= 21.6 V

Rated capacity of the battery pack = no.of cell in parallel* rated capacity of a cell
= 2 * 5.4Ah

= 10.8Ah

The model is for an 21.6V & with 10.8Ah battery capacity

Overall voltage of the battery pack = maximum voltage of the battery * no. of cells in series
= 8.3V * 3

= 25 v

Overall voltage = 25 V

Current, Voltage, SOC

Drive cycle

Conclusion :-

The battery pack configuration(3S2P) with generic battery block using Matlab/Simulink is created.