Float Charge in DC Power Supply System

Floating charging voltage refers to the voltage output by the rectifier during the process of connecting the rectifier and battery in parallel to the feeder line in a communication power supply system. When the mains power is normal, the rectifier supplies power and also provides a small supplementary current to the battery. This power supply method is called floating charging.

Float charging occurs after full charge has been reached, where a lower voltage (about 13.2 – 13.8 volts) is maintained to keep the battery topped off without overcharging it. This stage is crucial for long-term maintenance and ensures that batteries remain ready for use without deterioration over time.By keeping the battery at this voltage level, float charging prevents self-discharge while maintaining overall health.

UPS is widely used in computer rooms, data centers, and other places that require extremely high power reliability. During normal mains power supply, the UPS battery pack is in a float charging state, ready to provide power to the load in case of mains power interruption. Floating charging can ensure that the battery is always fully charged, ensuring fast and reliable power supply to the load at critical moments.

The nominal voltage of a single battery is 2 V, and the float charging voltage of a single battery is generally 2.23 V. The float charging voltage of a battery pack is generally set to 53.5 V (2.23 V × 24). For a 24V system, it means 12 batteries with a nominal voltage of 2V are connected in series, and the float charge voltage is 26.76V (2.23x12). For a 12V system, the float voltage is 2.23x6=13.38V.