Joint design of cell layout and balancing circuit for uniform aging in unmanned aerial vehicle battery packs

In a compact unmanned-aerial-vehicle (UAV) battery pack, the interior cells become hotter than the perimeter cells and therefore age faster. A series string is limited by its weakest cell, and this aging non-uniformity is fixed once the hardware is built. The module layout and the active-balancing circuit are usually selected separately, so this effect remains outside the design loop. In this work, we treat the layout, the balancing-topology family, and the conductor sizing as joint pre-fabrication variables, enumerate the small admissible design space, and score every candidate by a coupled electro-thermal-balancing-aging simulation, so that all designs are ranked under identical assumptions. On a 24-cell NMC 21700 string, the algebraic connectivity 𝜆 2 predicts the balancing speed well ( 𝜌 𝑆 = − 0 . 8 5 ), but it has no clear correlation with the long-term fade uniformity ( 𝜌 𝑆 = + 0 . 0 6 ). The uniformity is determined by the layout, through the fraction of cells on the cooled perimeter. A single thermal index of the layout collapses the fade spread of all layouts, of a wide interior-cooling sweep, and of the 12S–48S pack sizes onto one affine law ( 𝑅 2 = 0 . 8 9 ). Therefore, the high-connectivity cell-to-pack circuits are the heaviest, but they are no more uniform, and they are dominated. A light topology on the most-cooled layout produces about 28% smaller fade spread at a lower mass, and both gains are kept under closed-loop aging feedback. The first-cell life is about 11% longer in the open-loop case, but this value is an upper bound that the feedback reduces toward parity.