Challenge

Project 1

DDhiraj Shahaji Desai22 Mar 2023

Aim :

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.

Let , Given cell specification is 3.6 V nominal cell voltage with 3500 mAh

now, we have to design battery pack of 150 Kw with 120 V

calculate battery capacity in Ah

= 150 Kw /120

= 1250 Ah

Number of cells in series = Rated battey voltage / Nominal cell voltage

= 120 V / 3.6 V

= 33.33

Roundup the above value to the 34 to get rated battery voltage

Number of cells in parallal = Battery continoues current / Cell nominal capacity

= 1250 Ah / 3500 mAh

= 357.14

Roundup the above value to the 358 to get rated battery current.

Total no. of cells in battery pack = No. of cells in series* No. of cells in parallal

= 34*358

= 12172

From a datasheet of the battery the weight of the one cell is 4.6 gram determined so,

weight of the battery pack is 12172*4.6 = 56 Kg

To select sutiable topology only number of cells in series are taken into selection.

Types of topologies

1. Centralised Topology :

It used in battery packs which consits of 18 or less than 18 number of cells in series.

2. Master Slave Topology :

It used in battery packs which consits of 18 or more than 18 number of cells in series.

3. Modular Topology :

It used in battery packs which consits of 18 or more than 18 number of cells in series. But it used for bigger size battery pack like 1MW capacity.

4. Distrubutrd Topology :

It used in battery packs which consits of 18 or less than 18 number of cells in series.

In our case no of cells in series is 34 so Master slave Topology is best sutaible for it . so for this 34 cells are divded in the group of 18 cell per group, so 34 / 18 makes 1 groups of 18 cells and remanaing 16 in the 2nd number group.

b. Draw the BMS topology for this battery pack.

MASTER SLAVE TOPOLOGY :

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

Let,

Total no. of cells in battery pack = No. of cells in series* No. of cells in parallal

= 3*2

= 6

Model :

Above image shows the simulink model for the 3S2P battery pack. The voltage measurment block is connected acrooss the battery pack to measure the battery pack voltage. The scope output used for the battery pack consits of SOC , Current , Voltage . The controlled current signal is given as the load to the battery pack. The constant block is used to define the load.

The parameter given inside the battery is given below,

S.No Battery parameters Value

1 Nominal voltage of a cell 7.2V

2 Rated capacity of a cell 5.4Ah

3 Maximum voltage of a cell 8.3V

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

= 3 * 7.2 V

= 21.6 V

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

= 2 * 5.4 Ah

= 10.8 Ah

The model is for an 21.6 V 10.8 Ah battery.

The following figure shows the single battery output for SOC, voltage and current.

• 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

• Plot 3: The voltage is around 8.3 V. The increasing and decreasing voltage is with respect to the load

now,

Overall battery pack voltage = Max. Cell voltage* No cells in series

= 8.3*3

= 24.9 V

Project 1

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in your own course.

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Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.