Project 1 Mechanical design of battery pack
Question :-
Battery pack capacity: 18 kWh
Cell: ANR26650M1-B
Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.
Cell model number "ANR26650M1-B" are used to make a battery pack of capacity 18Kwh.
This is the high-performance Nanophosphate lithium iron phosphate (LiFePO4) cell.
Above model Cell specification are as follows :-
Cell dimensions = 25mm*65mm
Nominal cell voltage = 3.3 volt.
Cell capacity =2.5Ah
Weight of each cell = 76gram
Operating temperature = -30 degree c to +55 degree c
Storage temperature = -40 degree c to +60 degree c
Design a 18 kwh battery pach by using above cell model :-
Energy = Power * time
Energy = Voltage*Current*time
Energy = Voltage*Ampere*hour
Total energy capacity of battery = 18000watt hours
Mostly electric vehicle battery are designed for 400 volt to 800 volt.
Let's assume the electric vehicle battery voltage be 600 volt.
So, total ampere hour capacity of battery is calculated as :-
Total Ah capacity = Total energy of battery/Voltage of battery pack.
= 18000/600
Total Ah capacity = 30........................................(1)
Calculation of number of cells are connected in series branch(Ns) :-
Each cell nominal voltage =3.3 volt.
To obtained 600 volt from battery no. of cell are connected in sereis as follows :-
Total battery voltage = No. of cell connected in series(Ns)*Voltage of each cell
600 = Ns*3.3
Ns =600/3.3
Ns = 181.1 approx to 182 ................(2)
Calculation of number of parallel branches (Np):-
Each cell Ah rating =2.5Ah
In series connected cell Ah rating is same=2.5Ah
Total battery capacity = 30Ah so for that number of parallel branches connected as follows :-
Total battery capacity = No. of parallel connected branch (Np)*Ah rating of each branch.
30= Np*2.5
Np=30/2.5
Np =12
The configuration of battery we obtained as 182S12P,it means 182 cells are connected in series and similar 12 branches are connected in parallel.
Calculation of total weight of battery pack :-
Weight of each cell = 76 gram
Total cell in a battery pack =182*12=2184 cells
Total weight of battery pack = 76*2184 = 165.984 approx 166 Kg.
Calculation of dimension of battery pack :-
Dimension of each cell = 26mm*65mm
That is 26mm in diameter and 65 mm in height.
We are connecting the 182 cells in series in this fashion as shown in this image and similar 12 parallel branches are connected sisde by side .
All positive and all negative terminals are taken out from 12 branch and connected togethet to form 182S12P configuration.
So, dimension of battery pack are as follows :-
Length of battery pack = No. of cell *Diameter of each cell = 182*26=4732mm
Width of battery pack = 12*26 = 312mm
Height of battery pack = 65mm
Considering 10 % to 15 % more space for battery pack ,it is necessary if cell size increases due to heating,etc.
So, calculation of new dimension considering 15% tolerance:-
Length of battery pack = 709.8+4732=5441.8 approx 5442 mm
Width of battery pack = 46.8+312 =359mm
Height of battery pack = 9.75+65=74.75 approx 75mm