A Float-cum-Boost (FCBC) charger is a type of battery charger that combines two charging modes: float and boost

 A Float-cum-Boost (FCBC) charger is a type of battery charger that combines two charging modes: float and boost. It provides a continuous, reliable DC power supply to a load, while also charging the battery. In float mode, the charger maintains a fully charged battery and feeds the load. In boost mode, it quickly recharges a discharged battery after a power outage or heavy discharge. 

Here's a more detailed breakdown:

1. Dual Functionality:

Float Mode:

The charger maintains the battery at a fully charged state, providing a constant, trickle charge to compensate for self-discharge. This mode ensures the battery is ready to take over the load in case of a power outage.

Boost Mode:

When the battery voltage drops due to discharge, the charger switches to boost mode. This mode provides a higher charging current to quickly restore the battery's capacity. 

2. Applications:

Critical Loads:

FCBC chargers are commonly used in applications where a reliable and uninterrupted DC power supply is crucial, such as in telecommunications, substations, and industrial control systems.

Backup Power:

They provide backup power to critical loads in case of AC mains failure, ensuring continuous operation of essential equipment. 

3. Key Features:

Single or Dual Rectifiers:

FCBC chargers can be implemented with either a single rectifier (for smaller systems) or a dual rectifier setup (for larger, more critical applications). 

Automatic Mode Switching:

The charger automatically switches between float and boost modes based on the battery's state of charge. 

Protection Features:

They often include features like surge suppression, current limiting, and fuses to protect the battery and connected equipment. 

Efficiency:

FCBC chargers are designed to be efficient, minimizing energy waste during charging and operation. 

4. How it works:

In normal operation, the float charger feeds the load and trickle charges the battery. 

When a power outage occurs or the battery is heavily discharged, the charger switches to boost mode to quickly recharge the battery. 

The load is either fed directly by the float charger (in some configurations) or through a dropper diode while the boost charger is active. 

Once the battery is recharged, the charger returns to float mode.