Float charging is a method used to maintain a rechargeable battery at its fully charged state. In this process, a battery is connected to a continuous low-voltage power source that compensates for the self-discharge rate of the battery, keeping it at an optimal charge level without overcharging. This technique is commonly used for backup power systems, uninterruptible power supplies (UPS), and emergency lighting, where batteries need to be kept ready for use at all times. Float charging ensures the battery is always charged and extends its lifespan by preventing deep discharges and overcharging.