Project 1 Mechanical design of battery pack

AIM: 

        Prepare a detailed battery pack drawing of [Battery pack capacity: 18 kWh, Cell: ANR26650M1-B] along with its enclosure. State your assumptions.

Details of Cell: ANR26650M1-B:

ANR26650M1-B specification:

Nominal Rating:

• voltage :3.3 volts
• capacity:2.5Ah
• energy: 8.25Wh
• specific power: 2600W/kg
• impedence(1KHz AC typical) 6 mΩ
• cell type: 26650 lithium ion power cylindrical cell.

Discharging:

• max.continuous discharage: 50A 
• max pulse discharge current > 50% SOC (10sec): 120A
• minumum voltage:2 volts
• temperature: -30 to 55 degree celcious

charging:

• recommended std.charge: 2.5A
• max charge rate:10A
• max pulse charge current<50% SOC (10sec) :25A
• float voltage: 3.45 Volts

mechanical parameters:

• diameter: 25.96 +/- 0.5 mm
• length: 65.15+/- 0.5 mm
• mass : 76g

calculation as per assumptions: 18 KWh battery pack.

• calculation for designing an 18 KWh battery pack basically 18 KWh is energy require to achive the vehicle it proper range.and its depend on the voltage(V) and amp-hr capacity(Ah)

1] single cell energy(Wh) [the value of a single cell energy is used to calculate the total energy of the battery pack]:

single cell energy(Wh)= cell capacity(Ah)* cell voltage(V)

                                    = 2.5Ah *3.3V

                                    = 8.25 Wh

2] single cell volume calculation: 

single cell volume = pi(r^2)*h

                               = 3.14(0.013^2)*0.065

                               = 0.03451 m^3

3] single cell energy density:

A] volumetric energy(Wh/m^3) = single cell energy / volume of each cell

                                                    = 8.25Wh / 0.03451 m^3

                                                     = 239.0611 Wh/m^3

B] gravimetric energy(Wh/kg)   = single cell energy / single cell mass

                                                    = 8.25Wh / 0.076 kg

                                                    =108.5526 Wh/Kg

calculation of high voltage battery pack

for design and calculation of battery pack here,i assume a vehicle to achive 200km in 18 KWh battery pack also i assume 145.2 nominal voltage for series connection.

sowe assume that,

vehicle range = 200 Km 

battery pack capacity = 18.1210KWh

now, 

4] we will calculate per Km average energy requirement = 18120.96 (Wh)/200 (Km) 

                                                                                           = 90.60 Wh/Km

therefor, 

battery pack total energy = average energy * km

                                         = 90.60Wh * 200km

                                         = 18120.96 Wh

let's assume nominal voltage for seres connection= 145.2 V basically this depends upon the motor power,we can decide the value according to the motor.

5] number of cell connected in series = nominal voltage of seres connection/nominal voltage of a single cell

                                                            = 145.2V/ 3.3V

                                                            = 44 cell

44 cell will be connected in a series connection to provide a proper voltage.

6] energy for battery pack(Wh)  = number of cell connected in series * single cell energy

                                                    = 44* 8.25Wh

                                                    = 363 Wh

7]number of cell connected in parallel = battery pack total energy(Wh)/energy for battery pack(Wh)

                                                              = 18120.96 Wh/363 Wh 

                                                              = 50 cell

50 cell will be connected in a parallel to provide a proper capacity power.

8] battery pack total energy(Wh) = no. of cell connected in parallel * energy for battery pack

                                                      = 50* 363 Wh

                                                      = 18.150 KWh

9] battery pack capacity(Ah) = no. of cell connected in parallel * single cell capacity(Ah)

                                               = 50*2.5 Ah

                                               = 125 Ah

the value of battery pack capacity is used for the total power required by the vehicle.

10] total number of cell for battery pack = no. of cell connected in parallel * number of cell connected in series

                                                                 = 50*44

                                                                 =2200 cells

2200 cells will be used to make a complete battery pack.

11] mass of battery pack = total number of cell for battery pack * mass of single cell

                                         = 2200 * 0.076 kg

                                         = 167.2 kg

167.2 kg its the total weight of cell connected in parallel and series

12] total volume of the battery pack =  total number of cell for battery pack * volume of single cell

                                                           = 2200 * 0.0345 m^3

                                                           = 75.9 m^3

75.9 m^3 its the volume occupied by total cell used in battey pack.

13] cell peak current(A) = C rate(max pulse charge current)* single cell capacity

                                        = 20* 2.5

                                        = 50A

14] battery pack peak current(A) = cell peak current(A) * no. of cell connected in parallel

                                                      =50*50

                                                      = 2500A

15] battery pack peak power(W)  =  battery pack peak current(A) * voltage of series connection

                                                      = 2500 A * 145.2

                                                      = 363 KW

16] cell continuous current(A) = C rate(max continuous charge current)* single cell capacity

                                                  = 10* 2.5

                                                  = 25A

17] battery pack continuous current(A) = cell continuous current(A) * no. of cell connected in parallel

                                                                = 25*50

                                                                = 1250 A

18] battery pack continuous power(W)  =  battery pack continuous current(A) * voltage of series connection

                                                                = 1250 A * 145.2

                                                                = 181.5 KW

Details of Cell: ANR26650M1-B:

Battery holder:

Electric connection:

Battery pack with BMS[battery management system]: