Is parallel or series connection freely possible?

LiFePO₄ batteries can be connected in parallel or series, but only when the voltage (V) and state of charge (SOC) of each cell are the same to ensure stable operation. If the SOC or voltages do not match, a critical current imbalance may occur, which may result in cell damage or BMS triggering due to overcurrent. In particular, the presence of a cell balancing circuit is important when connecting in series, and each cell must be synchronized to a full state before connecting in parallel. Connecting without prior balancing may result in reduced lifespan, overheating, and in severe cases, fire hazard.