Project 1 Mechanical design of battery pack

The battery pack should consist of Cell: ANR26650M1-B .

Data sheet of ANR26650M1-B .

To construct an 18kwh battery packfor an EV application:

Assumptions:

Since EV motors require 400V source

So the voltage of the entire battery pack should be 400V.

Calculation

Total energy of the battery pack (Power output):18kwh

Total voltage output of the battery pack=400V

Voltage of each cell=3.3V

Nominal discharge current of each cell=2.5A

Power output of each cell=3.3*2.5=8.25Wh

No of cells required= 18000/8.25=2182 cells

In order to achieve the desired voltage, current and power from the battery pack, individual cells needs to be connected in both series and parallel combinations.

In series connection voltage is added across each cell and the current remains same thru alll the cells.

In parallel connection voltage across all the cells remain the same but current gets added up.

Hence to achieve 400V from each cell of 3.3V,

No of series connection=400/3.3=122 cells.

power output from 122 cells connected in series=no.of cells* power output from each cell=122*8.25=1006.5Wh.

But the desired power output is 18000 Wh.

so to attain that cells must be connected in parallel ie 18000/1006.5=18.

No of cells in parallel=18

Therefore 18 modules of 122 series connected cells must be connected in parallel

Hence it will be 122S18P battery pack.

Total no of cells in the battery pack is 122*18=2196 cells.

Total power output of the battery pack is 2196*8.25=18117Wh.

Total capacity of the battery pack(Ah)=18*2.5=45Ah.

Battery pack enclosure:

From the given data sheet of the cell,

length of cell=65mm

diameter of each cell=26mm

weight of each cell=76g

weight of the battery pack=2196*76=167 kg.

length of the battery pack=no of cells in series*(cell dia +Margin of both side of cells) + clearance=122*30+60=3720mm.

breadth of the battery pack=no of cells in parallel*(cell dia +Margin of both side of cells) + clearance=18*30+60=600mm.

height of the battery pack=height of each cell+wiring space+clearance=65+40+15=120 mm

The shape of the battery pack enclosure will be rectangular.