Project 1 Mechanical design of battery pack

Battery characteristics:

-Dimension of cell  Dia 26*65mm

-cell Weight 76g

Cell capacity -2.5Ah

Voltage- 3.3V

Impedance-6 mOhm

Power-2600W/Kg

Maximum Continuous Discharge-50A

Maximum Pulse Discharge (10 seconds)- 120A

Cycle Life at 20A Discharge, 100% DOD : >1000 cycles

As you can observe in power disharge characteristics  depending upon the discharging of battery the cell voltage reduces gradually.The smaller the discharge value better in the discharge characteristics.

2.5C constant current discharge at various temp.

when the battery  temp is within the specified limits it gives smoother curve. as the temperature incerses or decreases above or below the specifies limits the area gat narrowed.

Cycle performance: If the cell is discharged as per the given specification i.e 0.5C rate the capacity of the cells shows the maximum optimization of battery.

Given: to Model 18KWh battery using cell model ANR26650M1-B.

Datasheet : Nominal voltage-3.3V, Nominal cell capacity-2.5Ah,

Ans:  Considering 400V battery pack 

Cell Volume= pi/4 *D^2*h =3.142*0.026*.065=1.327*10^(-3)

cell energy=cell voltage*cell capacity=3.3*2.5=8.25KW.

Capacity of pack= Model capacity/ voltage of battery pack = 18000/400 = 45Ah.

1) To find the no. of cells in series and parallel

1-1 ) no. of cells in Series (Ns) = total  battery pack Voltage / nominal voltage  per cell = 400/3.3=121.12 appro 122 cells.

1-2)No. of cells in parallel(Np)= total battery pack current in Ah/ nominal current per cell = 45/2.5=18 cells

2) Total no. of cells required =  No. of cell in series * no. of cell in parallel=122*18=2196 cells

There fore our pack has 122S 18P cell.

Calculating dimensions of pack:

Length of battery pack= no. of cells in series * cell dia= 122 *0.026=3.17m approx =3.2m

Width of cell = No. of cells in parallel * cell dia = 18*0.026=0.468m aprrox=0.5m

Therefore ,

area of battery pack =Length of battery pack * width of battery pack= 3.2*0.5=1.6 m^2

Volume of battery pack= area of battery pack * height of battery pack=1.6*0.065=0.104m^3.

Total weight off battery pack= Total no. of cells * net weight per cell =2196*0.076=166.9Kg

Considering cost of each cell as 55 Rs

therefore cost of battery pack= 55* total no. of cells=55*2196=1,20,780Rs

Therfore for 400V 18KWh our battery pack cost around 1,20,780Rs.