Project 1 Mechanical design of battery pack

EV BATCH-17

Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

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

Aim:

To develop the mechanical design of a battery pack based on the required energy capacity.

Battery pack capacity: 18 kWh Cell: ANR26650M1-B

Objective:

• To design a battery pack whose energy capacity is eqaul to 18kwh.
• The battry pack should be developed from lithium -ion cells whose specification is ANR26650M1-B.
• While designing the battery pack relevant assumptions can be made and the same be stabbed in the report.

>> Stage of battery pack:

The various design elements to be considered while developing a battery pack are follows :

>> Electrical Design :

• Determine of capacity ,voltage and Current.
• High Voltage Isolation
• Short Circuit Prevention
• Efficient Power Delievery

>> Thermal Design :

• Improve pack efficiency.
• Mitigate thermal accidents.
• Increase pack life.

>> Mechanical design :

• Safe structure for extreme conditions.
• Cost productivity and reiabilty.
• Ease of assembly and service.
• Aesthetics,compactness and light weight.

>> Battery Management system (BMS) Design :

• Maintain cell/Pack operating limits.
• Prevent evemts compromisisng safety
• Control thermal systems.
• Communications and logitics.

>> Arrangement of battery pack:

• The type of terminals or connections to the external circuits depend on the current to be carried, the frequency with which the battery may be connected and disconnected, and the design of the circuit to which the battery will be connected.
• For low power circuits, gold plated contacts are the terminals of choice for connectors which are subject to frequent insertions. Gold is hard wearing, it has low contact resistance and doesn't oxidise.
• Flying leads with spade terminals or snap on studs are also used for low power applications.
• Metal tabs are also used on pouch cells. Terminals for high power applications are usually threaded metal studs to ensure a reliable connection. Safety requirements on high voltage batteries may also dictate shrouded terminals to prevent accidental exposure of the operator to dangerous voltages of the battery or to short circuits.
• Keyed terminals or connections are also advisable to prevent connection to incorrect chargers or loads.

>> Given data:

Required Energy capacity for the pack =18 kwh

Cell used for forming the pack = ANR26650M1B

>> Cell parameters used for the Mechanical Design process:

Cell Voltage = 3.3V

Cell Capacity = 2.5 Ah

Cell weight = 76g

Cell Diameter = 26mm

Cell Height = 65mm

Cost of each cell = $ 6.55

>> Mechanical construction :

Let us assume that the voltage of the battery pack (Pack voltage ) = 400volts.

We know that P = V*I,Hence we can calculate the pack capacity as follows.

Pack capacity = Energy capacity/Pack voltage

Pack capacity = (18*10^3)/400

= 45 Ah.

No of cells in series=Pack voltage /Cell voltage

= 400/3.3

= 121.21

No of cells in parallel = Pack capacity/ cell capacity

= 45/2.5

= 18 cells.

Total no of cells in the battery pack=(No Of Cells in series)*(No of cells in parallel)

= 122*18

= 2196 cells

Weight of battery pack =(No of cells in series)* (cell Weight) = 122*)/1000

=9.2772g

Length of Battery pack =(no of cells in the series) *(Cell diameter)

= 122*0.026

= 3.172m

Width of battery pack = (No of cells in parallel)*(cell diameter)

= 18*0.026

= 0.468m

Area of battery pack = (Length of the battery pack)*(Width of the battery pack)

= 3.172*0.468

= 148.45m^2

Volume of battery pack =(Area of battery pack) * (cell Height)

= 1.4845*0.065 = 0.0965 m^3

=96.5 litres

Specific Energy Density = Pack Energy Capacity/Weight of battery pack.

= (18*10^3)/167

= 107.78wh/kg

Volumetric Energy Density = Pack Energy Capacity/Volume of battery pack

= (18*10^3)/96.5

= 186.53 Wh/L

Cost of battery pack = (Total no of cells in the battery pack )*(cost of each cell )

=(2196*6.55)

= $ 14,383.8

= Rs 10,45,544.76