Project 1 Mechanical design of battery pack

Project 1 Mechanical design of battery pack

Aim:

Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.

Ans:

• 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 Discharge: 50A
• Max. Pulse Discharge Current > 50% SOC (10sec): 120A
• Minumum Voltage: 2 volts
• Temperature: -30 to 55 degree celcius

• 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 achieve 200km in 18 KWh battery pack also i assume 145.2 nominal voltage for series connection.

Some 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

Therefore,

Battery Pack Total Energy = Average energy * km

= 90.60Wh * 200km

= 18120.96 Wh

Let's assume nominal voltage for series 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 series connection/nominal voltage of a single cell

= 145.2V/ 3.3V

= 44 cells

44 cells 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 cells

50 cells 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

= 25 A

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]: