Project 4

AIM: To Calculate the capacity of the battery pack required and the number of series-parallel connections.For a vehicle of gross weight 300 kg, the motor ratings are 1200Wh, 65V. The range is 225km and the maximum speed is 60kmph.Give a stepwise discussion on how a battery pack is built.

Note: Choose any relevant lithium ion datasheet

A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The term battery pack is often used in reference to radio-controlled hobby toys and battery electric vehicles

First we have to Do calculation part for the find the battery pack capacity for this

Given Data,

Vehicle Weight=300kg

Motor Rating=1200wh.65V

Range=225Km

Max Speed=50 kmph

First we have to calcualte Motor Current

Power = V*I

1200 = 65*I

I = 1200/65

I = 18.46 A

Current withdrawn By Motor 18.46 Amp

Assure Current Loss 1-10%

After loss new motor current 18.46*1.05=19.38 amp

Now Calculate the Power requried at max speed

At 60kmph power= Voltage*Current

Power= 65*19.38

power=1260w

Now calculate Travel Foctor

Travel Factor= Total Range/ Total Speed

Travel Factor = 225/60= 3.75

To calculate Power based on Travel Factor

Power requried = Power*Travel Factor

power rquried=1260*3.75= 4725 = 4.7 kw

Now calculate Battery pack capacity based of efficiency

Battery pack efficiency 85-95%

we Consider 85%

Required Battery Pack Capacity= 47/0.85 = 5.52 kw

To Calculate Battery pack efficiency based on motor efficieny

Total Battery Pack capacity = 5.52/0.85 = 6.49 kwh

Now we have to find how many connections comes in series and parallel

Series Connection

Motor Voltage 65 V

Cell Volatge 3.7v

No of series cells. 65/3.7 = 18

18 cells in series

Parallel Connection

Motor Current 19.38 A

Cell current 2.8 A

No of parallel cells 19.35/2.8 = 7nos.

7 Cells in parallel


steps for bulding a battery pack

1)for designing a 6.49Kwh capacity battery pack we can take a lithium ion cells

2)As per above calculation we have to use 18cells in series and 7 cells are in parallel, do the parallel connection first and then connect all parallel connected cells in series this is ease the process to find a faulty cell while maintenance time

3)but before connecting them we have to check all are in balanced condition or not

4)cells are not in balanced condition then we have to Place a capping on cell as shown below image

5)Take cell holder and put a cell on it select the size of cell holder as per the size of cell.

6)after placing a cells in cell holder do the series parallel connection

7)for connection use a nickle strip and connect the nickle strip to the cells or battery pack use spot welding (if you do not have spot welding then use soldering method but it is not recommended because it produces more heat).

8)Now connect the Battery management system (BMS) to a battery pack.

9)By connecting voltmeter measure the voltage across BMS and check required voltage is getting or not.

10)after that enclose the battery pack by using epoxy sheet for safety purpose.

We have Calculate the capacity of the battery pack that is 6.49 kwh and also we find the number of series-parallel connections

that is series connections=18 cells in series,parallel connections=7 Cells in parallel and mention the steps for how to built a battery pack