Project 4

Aim : To calculate the capacity of the battery pack required and the number of series-parallel connections.

Objective : Give a stepwise discussion on how a battery pack is built.

Introduction :

• The widest use of battery packs has been in the Electric Vehicle (EV) industry which is projected to bring in a paradigm shift in the way we travel.
• An electric vehicle battery is often composed of many hundreds of small, individual cells arranged in a series/parallel configuration to achieve the desired voltage and capacity in the final pack. A common pack is composed of blocks of 18-30 parallel cells in series to achieve a desired voltage.

What is a Battery Pack?

• A battery pack is combination or made from battery modules, each of which is compose of battery cells.
• It it having series and parallel combinations of battery modules to form a required capacity of battery pack.
• Widely used battery packs are made up of Li-ion cells due its special features.

To calculate battery pack capacity and series parallel connections we are using given data and a Li-ion cell datasheet and moving step by step witg calculations to get the result.

Given data -

Vehicle gross weight - 300 Kg

Motor ratings - 1200 Wh, 65 Volt

Range - 225 Km

Maximum Speed - 60 Kmph

1) Step - To calculate battery pack capacity estimate -

• Vehicle gross weight - 300 Kg

• Motor ratings - 1200 Wh, 65 Volt

• Range - 225 Km

• Maximum Speed - 60 Kmph

2) Calculate current withdrawn by the motor - by using given data

• Power = Voltage x Current
• 1200 = 60 x Current
• Current = `(1200) / (65)` = 18.46 Amp`
• Current drawn by motor = 18.46 we are taking a roung feagure as 19 Amp
• Assume current losses = 1 to 10%
• = 19 x 1.05
• = 19.95 = 20 amp

with assuming losses, motor current = 20 Amp

3) Calulating power required at maximum speed

• Max speed 60 Kmph power required = Voltage x Current

= 65 x 20

Power at max speed = 1300 Watt

4) Calculate travel factor -

• The total distance traveled by an electric vehicle depends on the energy stored in the battery With its max speed.
• Travel Factor = Total Range / Total speed
• Travel Factor = `(225) / (60)` = 3.75

Travel Factor = 3.75

5) Power Based On travel factor -

• Power Required = Power at max speed x Travel factor
• Power Required = 1260 x 3.75 =4725 Watt

Power Required = 4725 Watt

6) Battery pack capacity based on efficiency -

• Battery pack capacity must be assumed as 85 to 95%
• Say efficiency is 90%
• Required battery pack capacity = Power required at travel factor / Efficiency
• Required battery pack capacity = `(4725) / (0.90)`

Required battery pack capacity = 5250 Watt i.e 5.26 Kw

7) Battery pack based on motor efficiency -

• Total Battery pack capacity = Required battery pack capacity / Efficiency
• Total Battery pack capacity = `(5.26)/(0.90)`

Total Battery pack capacity = 5.85 Kwh

8) Series & Parallel Connection :

Series Connection Calculation -

• Motor rating = 250 volt
• Cell nominal voltage = 3.7 volt
• No.of cells in series = Motor Voltage / Cell nominal voltage
• = 250/3.7 =67.56 =68

No. of series connections = 68

Parallen Connection calculation -

• Motor Current = 160 Amp
• Cell Current = 5 Amp
• No. of cells in parallel = Motor current / Cell current
• = 160/5 =32

No. of cells in parallel = 32

By the above calculation we are completed our aim, now its a time for our objective - That is Give a stepwise discussion on how a battery pack is built.

The steps to be followed while building a battery pack are as follow -

1. Component production - In which we are manufactured the anode and cathode active materials, electrolyte and separators.

2.Cell Production - Production and assembly of single cells are done in thid process

3.Module Production - Formation of cells into a larger modules which contains no. of cells that include some electronic management.

4.Pack Assembly - In this we are installation of modules toghether with system that manage power, charging and tempreture parameters.

5.Vehicle Integration - Integration of battery pack into into the vehicle structure, including battery car interface with connector , plugs and mounting process is done.

6.Use - After Completing all battery pack building process now its time to use it in specified EV which it is design for.

7. Recycle - If the battery pack is not working on its specified capacity then the battery pack is replace from thr vehicle and forwarded to recycling process

Results :

1. Using the given data of a vehicle we calculate the parameters required to build a battery pack which having total capacity of 5.85 Kwh
2. Then calculated the No. of series & parallel connections which are used in 5.85 Kwh of battery are 68S32P means 68 cells connection in series and 32 connections are in parallel.