Project 1 Mechanical design of battery pack
Here we have taken the ANR26650M1-b datasheet for 18kwh battary pack capacity , that was attached
what is battery:
A cell is a single unit of device that converts chemical energy into electrical energy.
A battery is a collection of cells that converts chemical energy into electrical energy.
All batteries are made up of three basic components: an anode , a cathode , and some kind of electrolyte (a substance that chemically reacts with the anode and cathode).This reaction causes electrons to flow through the circuit and back into the cathode where another chemical reaction takes place.
what is batttery pack:
A battery pack is a set of any number of identical batteries and They are configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power levels.
the individual batteries or cells, and the interconnections which provide electrical conductivity between them. Rechargeable battery packs often contain a temperature sensor, which the battery charger uses to detect the end of charging. Interconnects are also found in batteries as they are the part which connects each cell, though batteries are most often only arranged in series strings.
At the end of product life, batteries can be removed and recycled separately, reducing the total volume of hazardous waste.
battery selection and appliaction may contains mainly specific energy,power,safety,cost,performance and life spans
from the above specification of thr battery
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: > 1000 cycles
Discharging
Max Continuous Discharage: 50 A
Max Pulse Discharge Current >50% SOC (10s): 120 A
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 i am design a high voltage battery pack for an electric vehicle to achieve its range up to 220 km. For this calculation, I assumed 110 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
A module is designed in the configuration of 3s 5p
Series connection of a module = No. Of. cells x single cell voltage
Series connection of a module = 3 x 3.3
Series connection of a module = 9.9V
Parallel connection of a module = No. Of. cells x single cell capacity
Parallel connection of a module = 5 x 2.5
Parallel connection of a module - 12.5Ah
Energy capacity for a single module = 9.9 x 12.5
Energy capacity for a single module = 123.75wh
Let’s assume Nominal voltage for series connection = 220 V, Basically, this depends upon the motor power, We can decide the value according to the motor.
- Number of module's connected in series
= Nominal voltage of series connection / Nominal voltage of a single module
=110 V / 9.9 V
= 11.11
11 modules will be connected in a series connection to provide a proper voltage.
Energy for battery pack (wh)
power=voltage X current
18000=110X current
current=18000/110
current=163.63
so current is 163A
but for each module
163/12.5=13.04
13 modules will be connected in parallel to provide a proper capacity power.
Total no. of cells in the battery pack = 13 x 11 = 143 modules
Total no. of cells in the module = 3 x 5 = 15 cells
Total no. of cells in the battery pack = 143 x 15
Total no. of cells in the battery pack = 2145 cells
so finnaly 2145 cells are requried to achive the 18kwh power(143 module's are required i,e 3s5p)
2145 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
= 2145 x 0.076 kg
= 163.02 kg
Module Assembly
The cells are arranged in 3s5p. For the space storage and neat connection of cells, the position of the middle cell is changed the negative terminal is kept upwards.