Objective
Design and assemble a battery pack consisting of 12 18650 cells in 3s 3p, 2s 1p, and 1s 1p configurations for UBC's Cloudburst Rocket. Optimize design to fit within a 4-inch minimum diameter rocket, extensive testing at cell and pack level to validate the battery pack.
Specifications (3s 3p)
Cells Used: Sony VTC4 2100mAh 18650
Battery pack Nominal Voltage: 11.1V
Nominal Capacity: 6300 mAh / 69.93 Wh
Custom-designed Cell holders and 3D printer with PLA
Optimized star-shaped cell holders to fit battery pack into a 4-inch rocket
Testing and Validation
Cell-level testing
Each cell was tested for capacity and DCIR using the 10-channel automated characterization system before pack assembly
Established Threshold: Capacity > 1900 mAh and DCIR < 40 mΩ
Cell arrangement into series pack was done using https://www.repackr.com/ with cell data from the tester
Pack-level testing (Using ISDT K4)
Capacity @ 2.5A (0.42C) and 2.8V Cut-off: 6261 mAh / 69.4971 Wh
State of Health (SOH): 6261/6300 * 100 = 99.38%
Voltage Imbalance between cells just before Cutoff (Worst Case): 90 mV
Voltage Imbalance between cells just after Cut-off: 40 mV
Temperature: Pack remained cool during full discharge cycle (approximate 10°C increase)
Estimated Runtime for SRAD Avionics stack assuming Max Load (5V and 3.3V buck discharging 3A @ 85% efficiency): 2.37 Hours (142 minutes)
Estimated Capacity Left after running SRAD Avionics stack at Idle State for 5 hours (0.5A) and Max load for 1 hour: 18% (12.45 Wh left)
