Battery charger

Battery Charger

A battery charger is a device used to put energy into a secondary cell or rechargeable battery by forcing an electric current through it. The charging protocol depends on the size and type of the battery being charged.

Types of Battery Chargers

There are several types of battery chargers based on the way they control the charging rate:

• Simple charger: Works by supplying a constant DC power source to a battery being charged. The simple charger does not alter its output based on time or the charge on the battery. This simplicity means that a simple charger is inexpensive, but there is a trade off in quality.

• Trickle charger: The trickle charger is designed to be left on a battery for a long period of time to re-charge the battery. It slowly adds the charge to the battery and keeps the battery at an optimal charge.

• Timer-based charger: The output of a timer charger is terminated after a predetermined time. Timer chargers were the most common type for high-capacity Ni-Cd cells in the late 1990s for example.

• Intelligent charger: Also known as a smart charger, monitors the battery's voltage, temperature and/or time under charge to determine the optimum charge current at each stage of charging.

Charging Strategies

Depending on the design and chemistry of the battery, different charging methods can be applied. These include:

• Constant voltage: This method is most common for lead-acid and lithium-ion batteries. The charger applies a constant voltage, but allows the current to reduce as the battery becomes charged.

• Constant current: This method is often used for nickel-cadmium and nickel-metal hydride batteries. The charger applies a constant current, allowing the voltage to increase as the battery becomes charged.

• Pulse charging: In this method, charging consists of sending a series of short charging pulses to the battery, with a pause between pulse series.

Safety and Health Concerns

Battery chargers can pose safety and health risks. Overcharging a battery can cause a battery to overheat and may lead to the battery exploding. Some battery types are designed to handle overcharging, but others are not. It is important to understand the safety instructions for each type of battery before charging.