A BMS (Battery Management System) with a 3S configuration and 2A rating is an electronic circuit designed to protect and manage a 3-cell lithium-ion or lithium-polymer battery pack connected in series (3S). Since each Li-ion cell has a nominal voltage of 3.7V, a 3S pack provides about 11.1V nominal (12.6V fully charged and ~9V fully discharged). The 3S BMS 2A ensures safe charging and discharging of the battery pack by providing important protections such as: Overcharge protection – prevents any cell from being charged beyond 4.2V. Over-discharge protection – stops discharging when any cell drops below a safe voltage (around 2.7–3.0V). Overcurrent/short-circuit protection – prevents battery damage due to excessive current draw beyond 2A. Balancing (optional in some BMS) – ensures all three cells maintain equal voltage levels during charging and discharging for longer battery life. This type of BMS is commonly used in DIY battery packs, rechargeable devices, small UPS systems, LED lighting systems, and portable electronics, where a stable 12V (approx.) power supply is needed with moderate current consumption.