Project 1 Mechanical design of battery pack

Basically, 18kWh is the amount of energy needed to give the car its proper range, according to the calculations used to construct an 18kWh battery pack. It depends on the voltage (V) parameter, the ampere-hour, or the capacity (Ah). Here, we develop a high voltage battery pack for an electric car in order to maximise its 220 km range. Because of this in my calculation, I used a nominal voltage of 145.2 V for the series connection.

Single Cell Energy (Wh) = Cell Capacity (Ah) x Cell Voltage (V)
= 2.6 x 3.3
= 8.58 Wh.

The value of a single cell is used to calculate the total energy of the battery pack.

Single Cell Energy Density.
Volumetric energy (Wh/m^3) = Single Cell Energy / Volume of each cell
= 8.58 Wh / 0.03451 m^3
= 248.62 Wh/m^3.

Gravimetric energy (Wh/kg) = Single Cell Energy / Single Cell Mass
= 8.58 Wh / 0.076 kg
= 112.89 Wh/kg

I make the assumption that a car will travel 250 km on an 18 kWh battery pack for the purposes of this battery pack's design and computation. Additionally, I'm assuming a series connection at 145.2 volts nominal.

So,
Vehicle Range = 250 KM (assumed)

Battery Pack capacity = 18.121 kWh or 18120.96 Wh (For better and accurate calculation here I change kWh)
Now,
We will calculate per km average energy = 18120.96 / 250
= 72.483 Wh/km
Therefore,
Battery Pack total energy = Average energy x km
= 72.483 x 250
= 18120.96 Wh or 18.120 kwh

Let’s assume the Nominal voltage for series connection = 145.2 V

Basically, this depends upon the motor power, We can decide the value according to the motor.

Nominal voltage of series connection / Nominal voltage of a single cell =145.2 V / 3.3 V = 44.
The number of Cells is 44 in series .

44 Cells will be connected in a series connection to provide a proper voltage.
Energy for battery pack (wh) = No. of cells connected in series x Single-cell energy = 44 x 8.58 wh = 377.52 wh.

Number of cells connected in parallel = Battery pack total energy (wh) / Energy for battery pack (wh) =18120.96/377.52 = 48.
The number of Cells is 48 on parallel.

Battery pack total energy (wh) = No. of cells connected in parallel x Energy for battery pack (wh)
= 48 x 377.52
= 18120.96 wh or 18.120 kWh

Battery pack capacity = No. of cells connected in parallel x Single cell capacity (Ah)
= 48 x 2.6 Ah

= 124.8 Ah

Total number of cells for battery pack = No. of cells connected in parallel x No. of cells connected in series
= 48x44
= 2112

Cell peak current (A) = C rate (Max Pulse Charge Current) x Single cell capacity
= 20 x 2.6
= 52 A

Battery pack peak current (A) = Cell peak current x No. of cells connected in parallel
=52X48
= 2496 A

Battery pack peak power (W) = Battery pack peak current x Voltage of series connection
= 2496 A x 145.2
= 3624192 or 362.42 W

Cell continuous current (A) = Crate (Max Continuous Charge Current) x Single cell capacity
= 10 x 2.6
= 26 A

Battery pack continuous current (A) = Battery pack continuous current x Voltage of series connection
=1248 x145.2
= 18120.96 or 18.120 kWh

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Power (p)= Voltage (v) * Current (i) kw =3.3 *2.5 =8.25 kw
To get 18kwh ,we are assuming 48s 48p which is 48*48 =2304 cells

In series connection 48*3.3 =158.4 v
In parallel connection gives 48* 2.5 =120 A
we can get 158.4* 120 =19.008 kwh energy or capacity.With battery spacers to hold the cells and nickel strip for their connection, we design battery packs for 48s and 48p cells. To prevent cell damage when cells are joined by a nickel strip, spot welding should be utilised.