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.

SOLUTION :

To make the battery pack, we have to first finalize the nominal voltage and capacity of the pack. Enter it wiil be in term of Volt, mAh/Ah or Wh.

Total required battery pack capacity is 18000Wh

The individual cell : ANR26650M1-B has

Nominal voltage= 3.3v

current capacity = 2.5Ah

so, let us assume that for 18kwh battrey pack we need supply voltage of 200v and 90Ah.

200v = 3.3* cell in series.

Cell in series = 200/3.3 = 60.60 = 60

Now,as we know that battery pack capacity(Wh) = Total current*Total voltage =(2.5*cell in parallel)*200

18000 = (2.5*cell in parallel)*200

Cell in parallel = 18000/(2.58200)=36

Module capacity

The required battery pack combination is 60s36p.

for this we decided to choose 5series and 3 parallel module connection

Each 5s3p confugration module voltage capacity = 5*3.3 = 16.5v

so, the total capacity of 1 module is = 16.5*7.5 = 123.75wh

TOTAL CELLS

total number of cells = cell in 1 module *144

Total number of cells = (5*3)*144

Total number of cells = 2160*8.25

Total cells capacity = 17820wh = 17.82kwh

we should always target more KWH then required considering the losses and connection limitations

weight of one cell = 76g = 0.076kg

so, battery pack cell weight = 0.076*2160 = 164.16kg

MODULE CONNECTION

for 18kwh of total 200v and 90ah battery pack capacity we need 18000/123.75 = 145.45modules

STEP 1 : select the ANR26650M1-B cells for the battery pack

STEP 2 : Check the cell voltage

before coonecting the cells in parallel, first check the individual cell voltages.

For paralleling the cells, the voltage oof each cells should near to each other, otherwise a high amount of current will flow from the cell with higher voltage to the cell with lower voltage.

This can damage the cells and even result in fire on rare occasions.

Step 3 : Assemble the ANR26650 M1 -B cells

A battery management system (BMS) is any electronic system that manages a lithium battery pack and the main functionalities are :

Monitors all of the parallel groups in the battery pack and disconnect it from the input power source when fully charged.

Balance all the cells voltage equally.

Doesn't allow the pack from over-discharged.

The battery pack have all around exposed nickel strips , to avoid any accidental shorting an ENclosure used.