Understanding how to connect these batteries in series or parallel is crucial for optimizing performance and ensuring efficient energy use. This guide explains the differences between these connection methods and how to implement them effectively. However, wiring lithium. Our ISO 9001-certified manufacturing facilities and IEC 62133-compliant designs ensure that every 18650 battery pack, Li-ion, lithium polymer, and LiFePO4 system delivers unmatched safety, energy density, and cycle life. In a series connection, the voltage increases while the capacity remains the same, making it suitable for high-voltage applications.