Project 1

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

1. Design the battery pack configuration. 
2. Draw the BMS topology for this battery pack.

Ans-

1. Design the battery pack configuration. 

Given Data,

Maximum Voltage/Rated voltage = 120V

Nominal Voltage = 3.6V

Capacity of Cell = 3500mAh = 3.5Ah

Power rating = 150 KW = 150000 W

We have to calculate the Battery pack configuration i.e. cells in series & parallel

we have formula,

Cell in Series = Rated voltage/Nominal voltage

Cell in Series = 120/3.6 = 33.33 V

The number is in decimal so we have to round it off. so we round it off to 33 & 34 check the required criteria

i.e. Battery minimum voltage > Motor minimun voltage &

Battery maximum voltage < Motor maximun voltage

Case1                                                                          Case2 

Rounding of 33.33 Cell to = 33                                  Rounding of 33.33 Cell to = 34

• Nominal Voltage = 3.6*33 = 118.8 V                              Nominal Voltage = 3.6*34 =122.4 V
• Maximum Voltage = 4.2*33 = 138.6 V                            Maximum Voltage = 4.2*34 = 142.8 V
• Minimum Voltage = 2.7*33 = 89.1 V                              Minimum Voltage = 2.7*34 = 91.8V

• So from the Case 1 & Case 2 the idle series combination who fulfill the criteria is case 2.

  So by rounding off the No of cells in series is 34.

  we have formula,

  Cells in Parallel =Total continuous current / Capacity of cell

  Total current = Power rating / Maximum voltage

  Total current = 150000 / 120 = 1250 A

  Cells in Parallel = 1250 / 3.5 = 357.14

The number is in decimal so we have to round it off. so we round it off to 357 & 358 check the required criteria

i.e. Individual cell Peak current > Cell maximum discharge current 

Individual cell Peak current < Cell maximum discharge current 

So by Rounding off the no of cells in Parallel is 358.

So the Battery Pack Configuration required by iPhone 8 is 34S358P.

2.Draw the BMS topology for this battery pack.

Ans- Based on the number of cells in series & Applicaion we are choosing the correct BMS topology.

Here the no of cells in series is 34. So the cells is greater than 18 & for 4 wheeler car is given that's why we are using Master Slave Topology.

Master Slave Topology.

• These master Slave topology is used when the number of cells in series is more then 18.
• It is generally used for 4 wheelers & large energy storage pack system.
• Slave 1 having 17 cells & Slave 2 also having 17 cells.
• These Slave 2 is now communicating with Microcontroller.
• Scalability is possible
• Can read more than 18 cells maximum in series.

As per our requirement i'm connecting 17 cells in series with the respective slave