Battery pack capacity: 18 kWh

Cell: ANR26650M1-B

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

A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The term battery pack is often used in reference to cordless tools, radio-controlled hobby toys, and battery electric vehicles.

Components of battery packs include the individual batteries or cells, and the interconnects 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.

When a pack contains groups of cells in parallel there are differing wiring configurations which take into consideration the electrical balance of the circuit. Battery regulators are sometimes used to keep the voltage of each individual cell below its maximum value during charging so as to allow the weaker batteries to become fully charged, bringing the whole pack back into balance. Active balancing can also be performed by battery balancer devices which can shuttle energy from strong cells to weaker ones in real time for better balance. A well-balanced pack lasts longer and delivers better performance.

For an inline package, cells are selected and stacked with solder in between them. The cells are pressed together and a current pulse generates heat to solder them together and to weld all connections internal to the cell.

ANR26650M1B Lithium Ion Cylindrical Cell

Nanophosphate ANR26650M1-B: The ANR26650M1-B is the next generation of A123 Systems’ pioneering 26650 cylindrical cell, now with greater power and energy density and lower impedance. This versatile lithium ion cell is suitable for a wide variety of applications and system designs. Proven performance in the toughest conditions, combining durability, reliability, and safety, the ANR26650 cell offers an excellent combination of price-performance.

Cylindrical Cell Primary Applications:

• Portable high power devices
• Stationary battery backup systems
• Grid stabilization energy storage systems
• Commercial truck and bus hybrid electric vehicles (HEVs)

Lithium Ion Cell Benefits:

• Power: Over 2,600 W/kg and 5,800 W/L
• Safety: Excellent abuse tolerance and environmentally friendly
• Life: Excellent calendar life, 10X cycle life vs. conventional lithium ion

Cylindrical Cell Specifications:

• Cell Dimensions (mm): Ø26 x 65
• Cell Weight (g): 76
• Cell Capacity (nominal/minimum, Ah): 2.5/2.4
• Voltage (nominal, V): 3.3
• Internal Impedance (1kHz AC typical, mΩ): 6
• HPPC 10 Sec Discharge Pulse Power 50% SOC: 200 W
• Recommended Standard Charge Method: 1C to 3.6V CCCV, 45 min
• Recommended Fast Charge Method to 80% SOC: 4C to 3.6V CC, 12 min
• Maximum Continuous Discharge (A): 70
• Maximum Pulse Discharge (10 seconds, A): 120 A
• Cycle Life at 10C Discharge, 100% DOD: >1,000 cycles
• Operating Temperature: -30°C to 55°C
• Storage Temperature: -40°C to 60°C