Q)

Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

Prepare a detailed battery pack drawing along with its enclosure. State your assumptions.

ans -

Cell: ANR26650M1-B specifications

calculations are made with some assumptions

https://a123batteries.com/anr26650m1-b-lithiumwerks-nanophosphate-3-3v-2-5ah-lithium-iron-phosphate-battery/

ANR26650M1-B Specifications
Nominal Ratings
Voltage: 3.3 Volts
Capacity: 2.5 Ah
Energy: 8.25 Wh
Specific Power: 2600 W/kg
Impedance (1KHz AC Typical) 6 mΩ
Cycle Life at 1C/1C, 100% DOD: > 4000 cycles
Cell Type: 26650 Lithium Ion Power Cylindrical Cell

Discharging
Max Continuous Discharage: 50 A
Max Pulse Discharge Current >50% SOC (10s): 120 A
Minimum Voltage: 2 Volts
Temperature: -30ºC to 55ºC

Charging
Recommended Standard Charge: 2.5 Amps
Max Charge Rate: 10 Amps
Max Pulse Charge Current <50% SOC (10s): 25 A
Float Voltage: 3.45 Volts
Recommended charge V & Cut-off Current: 3.6 Volts, taper to 125mA
Temperature
(reduce charging current to 250mA when under 0ºC): 0ºC to 55ºC

Mechanical
Diameter: Ø25.96 +/- 0.5 mm (1.0")
Length: 65.15 +/- 0.5 mm (2.6")
Mass: 76 g

Calculation as per assumptions:- 18kWh Battery Pack

calculation for designing an 18kWh battery pack, basically 18kWh is energy require to achieve the vehicle its proper range. It is depending upon the voltage (V) parameter and ampere-hour or capacity (Ah).

Here we design a high voltage battery pack for an electric vehicle to achieve its range up to 220 km. For this calculation, I assumed 145.2 V a nominal voltage for series connection.

Basically, the value of the volume of the cell is used to find out the total volume of the battery pack.
- 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

Calculation of High Voltage Battery Pack
For design and calculation of battery pack here, I assume a vehicle to achieve 250 km in 18 kWh battery pack. Also, I assume 145.2 nominal voltage for series connection.
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

Therefor,
Battery Pack total energy = Average energy x km
= 72.483 x 250
= 18120.96 Wh or 18.120 kwh

Let’s assume Nominal voltage for series connection = 145.2 V, Basically, this depends upon the motor power, We can decide the value according to the motor.
- Number of cells connected in series
= Nominal voltage of series connection / Nominal voltage of a single cell
=145.2 V / 3.3 V
= 44

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

48 cells will be connected in parallel to provide a proper capacity power.

-- 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

The value of battery pack capacity is used for the total power required by the vehicle.
-- Total number of cells for battery pack

= No. of cells connected in parallel x No. of cells connected in series

=48x44

= 2112

2112 Cells will be used to make a complete battery pack.
-- Mass of battery pack

= Total no. of cells for batter pack x Mass of single cell

= 2112 x 0.076 kg

= 160.512 kg

it is the total weight of cells connected in parallel and series.

-- Total volume of the battery pack
= Total no. of cells for batter pack x Volume of single cell
= 2112 x 0.0345
= 72.89 m^3

This is the volume of2112 cells which are used in the battery pack system.

-- 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

It is used for the operation of the battery pack. By this way, a vehicle will decide how much power is required to move.

-- 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)

= Cell continuous current x No. of cells connected in parallel

= 26 x 48

= 1248 A

This is the power which is supply continue to the whole battery pack system.

-- Battery pack continuous power (W)

= Battery pack continuous current x Voltage of series connection

=1248 x145.2

= 18120.96 or 18.120 Kwh

detailed battery pack drawing along with its enclosure.

BATTERY HOLDER ,SPACER For CELL CYLINDRICAL LI-ION

Design Benefits
• Up to 50 percent lighter than an equivalent steel design
• Best-in-class mass energy density at more than 160
watt-hours per kilogram, an extremely efficient design
for OEMs and Tier 1 battery pack manufacturers.
• Accommodates all battery cell types and is designed
particularly for battery electric vehicles with larger
power packs such as pick-up trucks, sport utility
vehicles and crossovers.
• Most cost-effective aluminum solution for mass
production electric vehicles when compared to
aluminum extrusion and casting-intense designs.
• Low price premium on $/kg saved compared
to equivalent steel designs at substantially
lower weight.

https://www.novelis.com/automotive/electric-vehicle-battery-enclosure/

as we know now

Power (p)= Voltage (v) * Current (i) kw

3.3 *2.5 =8.25 kw

To get 18kwh ,we are assuming 48s 48p

i.e; 48*48 =2304 cells

series connection gives 48*3.3 =158.4 v
parallel connection gives 48* 2.5 =120 A
from this we can get

158.4* 120 =19.008 kwh energy or capacity.

we design battery pack for 48s and 48p cell along wth battery spacers to hold cells and for their connection nickel strip is used

when cells are connected by nickel strip spot welding should be used so that cell not get damage.

final form

on the below website you can calculate battery parameters online

https://x-engineer.org/automotive-engineering/vehicle/electric-vehicles/ev-design-battery-calculation/#:~:text=The%20high%20voltage%20battery%20it,maximum%20regeneration%20brake%20torque