Project 1 Mechanical design of battery pack
Mechanical design of battery pack
Recommended cell : ANR26650M1-B
Battery pack capacity requirement: 18 kWh
Battery data sheet and specification
https://www.batteryspace.com/prod-specs/6610.pdf
ANR26650M1-B is high-performance lithium iron phosphate (LiFePO4) battery
Lithium Iron Phosphate is most popular and safest battery ever because the chances of explotion is too low, as well as most of the chinese automotive manufacturers prefers Lithium iron phosphate
In this battery Iron and phosphate is used as cathode material, Lithium and Graphite are used as Anode material. By using Iron in cathode, weight of the battery is increases, due to this the energy density decreases. so
the energy density of lithium iron phosphate is 90-120 Wh/kg
C-rating
Charging =1c
Discharging =2c we can get more power output by short period of time, so the vehicle initial acceleration will be higher.
Life cycle = 2000 to 3000
Battery pack
Battery pack is purely based on vehicle power requirement which is nothing but actual vehile load which is experienced by the motor eg: Forces acting on vehicle(Aerodynamic force, rolling resistance, hill climbing), acceleration, weight, top speed etc. these parameters will give vehicle power.
From drive cycle data we can calculate the capacity required for an given range expectation, if we have the expectation range then we calculate energy required.
Here we have agiven data of Battery pack capacity =18kwh.
According to A123 system ANR26650M1-B cell configurations are listed below
Voltage: 3.3 Volts
Capacity: 2.5 Ah
Energy: 8.25 Wh
Cell dimensions
Diameter: Ø25.96 +/- 0.5 mm
Length: 65.15 +/- 0.5 mm
Mass: 76 g
Voltage selection
Battery electric vehicles typically have operating voltages of 200-800 Volts
Here i take 300V
Voltage = 300v
Battery capacity
Battery capacity=18000/300
Battery capacity =60Ah
we know Energy capacity and operating voltage, now we have to calculate Number of cells
Range
Here we are determining Energy available/Energy required that gives range
RAnge= usable capacity/Wh/km
Lithium ion batteries are 80% usable so 18000*0.8=14400wh
Wh/km is measured from drive cycle data assuming 150 Wh/km
Range= 96km
No. of cells in series = Vb/Vc
Vb=battery voltage
Vc=cell voltage
Ns=300/3.3
Ns=91
Number of cells in Parallel
Np=60/2.5
Np=24
Total number of cells = 2184
Volume of battery pack
While arranging the cells in battery they are not going to sticking together completly, there is some gap inbetween them for thermal management, so i am not going to consider as cylinder but assume its cuboid, so that i`m going to calculate volume for that.
Cell dimensions are
Diameter: 25.96mm
Length: 65.15 mm
volume =28*28*65.15mm^3
volume of battery pack is 111.55 litre
Weight of the battery pack:
total no. of cells * weight of one cell
weight=166kg
Note: The overall weight of the battery is further increased by the use of the battery management systems, cooling and safety system, as well as by the assembly box for the battery modules.
Gravimetric energy density 108.4 Wh/kg
Volumetric energy density 161.36 Wh/l
| Parameters | |
| Total Pack capacity(given) | 18Kwh |
| cell Voltage | 3.3V |
| cell capacity | 2.5Ah |
| cell energy capacity | 8.25wh |
| Battery pack voltage | 300V |
| Battery capacity | 60Ah |
| Range | 96km |
| No. of cells in series | 91 |
| No. of cells in parallel | 24 |
| Total no. of cells | 2184 |
| Volume of battery pack | 111.55L |
| Weight od battery pack | 166kg |
| Gravimetric energy density | 108.4 Wh/kg |
| Volumetric energy density | 161.36 Wh/l |
Reference: