Project 1 Mechanical design of battery pack

Cell: ANR26650M1-B

Assume the battery voltage is 72 V

Series cells

Number of series cells = Total voltage ÷ Nominal cell voltage

Total voltage = 72v

Nominal cell voltage = 3.3v

Number of series cells = 72 ÷ 3.3

= 21.8

= 22

Parallel cells

Number of parallel cells = Total Ah ÷ Cell capacity

kWh ÷ V × 1000 = Ah

Battery capacity = 18 ÷ 72 × 1000

= 250 Ah

Number of parallel cells = 250 ÷ 2.5

= 100

Total cells

Total number of cells = Number of series cells × Number of parallel cells

Total cells = 22 × 100

= 2200

DIMENSIONS OF BATTERY PACK

Cell dimension = 26 x 65 mm

• This pack contains two modules
• Each module contains 1100 number of cells with 22 series and 50 parallel cells
• These two modules connect in parallel to get 72 V , 250 Ah battery pack

Size of holder for single cell = 27.5 mm

Length of pack = 27.5 x 50

= 1375 mm

Width of pack = 27.5 x 22

= 605 mm

Height of pack = 2 x 65 + 4 x 8

= 162 mm

Volume of pack = 134764 m³

WELDING PROCESS

ULTRASONIC WELDING (UW)

It is one of the most commonly used welding methods in the manufacturing of battery systems

It utilizes High-Frequency Ultrasonic Vibration (20kHz or above), to join substrate materials by creating solid-state bonds under clamping pressure

The welding technique which can weld dissimilar material better, with minimum defects, and can weld highly conductive material together, is Ultrasonic Welding

Nickle Strip is generally useful in the welding of battery points together to connect the batteries in combinations.

These Nickel strips are popular because of :-

• High resistance to corrosion
• High Tensile Tension.
• Low Resistivity.
• Useful for battery points welding

BATTERY PACK CASE

Thin walled large aluminum casting achieving high stiffness and light weight. This casing provides vents for air circulation and cooling

Battery Management System

Customized BMS for different battery packs based on applications are available.

• Current & Voltage Protection
  • Protects the battery pack from over-charge and over-discharge thereby extending cycle life
• Health Monitoring
  • Monitors internal resistance of individual cells and the measured capacity of the battery pack
• Thermal Management
  • Over-temperature and under-temperature protection with fan controls for cooling or heating
• State of Charge Monitoring With Drift
  • Coulomb counting and dynamic drift correction are used to monitor the state of charge
• Digital & Analog Output Controls
  • Provides multiple methods of controlling chargers, motor controllers and other external devices
• Intelligent Cell Balancing
  • Efficient passive balancing is used to maximize the usable capacity of battery packs
• Field Programmable
  • Parameters such as voltage ranges, current limits and many other settings are easily field changeable

References:-

https://batter-tech.com/index.php/product/18650-21700-26650-32650-lithium-battery-holder/

https://e-vehicleinfo.com/welding-methods-for-electric-vehicle-battery-systems/

https://www.orionbms.com/?gclid=EAIaIQobChMI4Mq7gvuX_AIVQUwrCh2COwvAEAAYASAAEgJdi_D_BwE