Project 4
For a vehicle of gross weight 300 kg, the motor ratings are 1200Wh, 65V. The range is 225km and the maximum speed is 60kmph. Calculate the capacity of the battery pack required and the number of series-parallel connections. Give a stepwise discussion on how a battery pack is built.
Note: Choose any relevant lithium ion datasheet
Answer:
First we have to Do calculation part for the find the battery pack capacity for this
Given Data is 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Current withdrawn By Motor 18.46 Amp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 find how much connection 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
Now,
Following 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.