The traditional multicell battery design usually employs a fixed configuration to connect multiple cells in series and parallel during operation in order to achieve the required voltage and current. However, this fixed configuration results in low reliability, low fault tolerance, and nonoptimal energy conversion efficiency. This paper proposes a novel self-reconfigurable, multicell battery design. The proposed multicell battery can automatically configure itself according to the dynamic load/storage demand and the condition of each cell. The proposed battery can self-heal from failure or abnormal operation of single or multiple cells, self-balance from cell state variations, and self-optimize to achieve the optimal energy conversion efficiency. These features are achieved by a new cell switching circuit and a high-performance battery management system (BMS) proposed in this paper. The proposed design is validated by simulation and experiment for a 6×3-cell polymer lithium-ion battery. The proposed design is universal and can be applied to any type and size of battery cells.