What Is Battery Charger?

A battery charger is an electrical device that charges the battery in a battery-powered device. The chargers provide constant voltage to the cells while monitoring individual cell response to ensure full charge without overcharging or undercharging any cell.

Components of Battery Charger

1. A rectifier circuit

2. Power circuit

3. Ripple monitoring

4. Control circuit 

5. Regulator circuit

6. Fault detection circuit

1. A Rectifier Circuit 

The rectifier circuit is an AC (Alternating Current)-DC (Direct Current) converter. It converts the AC input voltage to DC output voltage. The battery is connected in parallel with the rectifier circuit through the fuse. A fuse protects the whole circuit to prevent any damage to it or loss of power. The fuse saves the system from short-circuiting and overcharging of batteries, which can result in explosions, fires, and severe property damages

2. Power Circuit 

This comprises capacitors and inductors that act as filters to smooth out high-frequency ripple disturbances on the power supply lines for better charging performance of batteries. The power circuit can also filter out DC droppings on the DC output voltage.

3. Ripple Monitoring 

The battery charger employs several components to monitor and control the process of charging. They work together to keep each cell’s charge voltage and current in the battery pack at the proper levels. Float charging, absorption charging, and trickle charging are among the algorithms used by the chargers to monitor and manage charging conditions.

The circuit uses several electronic components or signal processors to regulate battery charge voltage. These usually are internalized in all chargers except trickle chargers. A microcontroller unit (MCU) is an integrated circuit designed with low-power analog circuits integrated within a single silicon chip on a printed circuit board (PCB).

4. Control Circuit 

This is an integrated circuit that performs many functions. One of these is to control the switching operation of a power MOSFET transistor. Another part is to deliver status information from the charge control circuit to the user or electronic device. This includes information about the state of charge of the battery.

5. Regulator Circuit 

The regulator circuit ensures that the output current supplied by the rectifier is accurate at all times. This ensures that no overcharging will occur, which could lead to explosions or fires. The regulator circuit protects against overcharging by lowering its output current if it senses an error or fault in any part of the charger circuitry, including overcharging of batteries, short-circuiting, incorrect input voltage levels, and incorrect input frequency levels.

6. Fault Detection Circuit 

The control circuit detects faults, including full charge or low charge, and takes appropriate actions to bring the battery to its optimal state. For example, if the battery is fully charged but the charger needs another 10 percent charging. It may disconnect from the DC power supply and continue charging at the trickle rate until the final voltage reaches a fully charged battery. Once this occurs, it will reconnect to the power supply and switch itself to absorption mode for up to four hours depending on how much charge was lost, resulting in excessive heating of internal components.

Functions of Charger

There are three functions of battery charger

1. Charging

2. Stabilizing

3. Terminating

1. Charging 

Charging is the process of putting energy into a battery by forcing an electric current through it. A battery charger provides the necessary voltage and current to perform this action, taking electricity from a wall socket, solar panel, or other power source and transforming it into the correct voltage and current parameters required to charge a specific battery model. The charger will also monitor the charging process and stop or limit current flow if any abnormal conditions occur (for example, abnormally high temperature or too much pressure). 

2. Stabilizing

Whether they be Ni-Cd, Li-Ion, or a combination of the two, batteries may begin to develop problems as they age. Their ability to hold a charge starts to diminish as their chemical composition changes. In “normal” use, these changes may not be noticeable, but as time goes on, they can cause an increase in capacity loss and battery capacity degradation

3. Terminating

The termination stage is where the charging cycle is completed, and a fully charged battery is ready for use in a device requiring a rechargeable battery. Batteries should be sent to this stage of the charging cycle using a battery monitor or tester; these devices measure the voltage and current delivered to the battery undercharge. After this, the charger will apply to equalize current, equal to 1.2 times the battery’s capacity. It is performed at different rates for different types of batteries. If not fully charged by this point, allow it 1–2 hours for each stage until you see that it is fully charged.

Types of Charger

1. Switch Mode Regulator (Switcher)

Switchers are the most common type of charger. They are also called wide input voltage or high-efficiency battery chargers. A switcher automatically adjusts the output voltage to match the battery being charged so that it can charge any size, capacity, or type of rechargeable battery, including Li-Ion. Switchers are the best choice for charging today’s more exotic and higher-capacity batteries found in laptops and cellular phones.

2. Constant Current (CC) Charger

A CC charger produces a constant current of volts or amp to the battery. These chargers are often used for charging Nickel Cadmium (NiCd) batteries. The reason for this is that NiCd batteries cannot accept a fast charge.

3. Constant Voltage (CV) Charger

A constant voltage charger generates a regulated output voltage and maintains it until the battery is fully charged. These chargers are often used for charging Lead-acid batteries because lead-acid batteries can be damaged by overcharging. You can also use CC/CV chargers for this purpose.

4. Floating Voltage (vf) Charger

VF chargers are helpful when charging two or more different types of batteries. For instance, if you wanted to charge three 1.2 V NiMH batteries along with a 9 V NiMH battery, you could use a floating voltage charger. The charger levels out the different voltages and charges all the batteries at the same time.

5. Pulsed Charger

A pulsed charger uses a constant current output to charge the battery, yet the output is pulsed or interrupted in regular intervals.


By reading the above article, you will know why a battery charger is necessary for your portable electronics. It will also help you decide what type of charger to purchase for your needs.