Project 1 Mechanical design of battery pack
The datasheet values of ANR26650M1-B cell is given below
Voltage- 3.3 V
Capacity- 2.6Ah
Energy- 8.25 Wh
Assuming the voltage required for the motor is 72 V
Series cells
No of cells in series=72/3.3=22
Therefore we need 22 ANR26650 cells in series connection
The total capacity C= Energy/voltage=18000/72=250Ah
Parallel cells
No of cells in parallel= 250/2.6=97
We need 97 ANR26650 cells in parallel connection
Therefor the total number of cells required for 18KWh battery pack is
No od cells in series* No of cells in parallel
22*97=2134 cells
Therefore to build a battery pack with 18KWh( 72V, 250Ah) we need 2134 cells( 22 in series and 97 in parallel)
Due to high discharge, temperature and leakage we must create 2 KWh extra energy. Therefore we must create 20KWh energy battery pack.
Assuming 145V motor
Number of cells in series=145/3.3=44
Therefore we need to connect 44 cells in series
Total capacity C=Energy/voltage=20000/145=138Ah
Number of cells in parallel= 138/2.6=54
Therefore we need 54 cells in parallel.
Total cells= Cells in series*cells in parallel
= 44*54=2376 cells
Now we have to create a battery pack with 44 cells in series and 54 cells in parallel
Assuming we are connecting 3 cells in series and 6 cells in parallel to form a module then
3*6=18
There will be 18 cells in a module
Therefore we have to create 2376/18=132 modules.
This figure shows 3S6P module and similar to this we need 132 modules to buils our battery pack.
Next spacers are used to hold these cells with certain gap in order to maintain the temperature.
The dimension of the above said spacer module is given below
After placing all the 132 modules as shown below
The nickel strips are used to connect the batteries as shown below
After all the batteries are connected its time for preparing the outer casing.
The outer casing is prepared according to the dimensions of the battery pack and a common + and _ terminals are taken out from the casing for connecting with the load.
The casing must be designed properly such that it does not allow water to get into the casing.