Battery Charger

Battery charger instruments are idevices that conduct energy into a battery cell by forcing an electric current through it. This electrical charge depends upon the tyype and design of the battery being charged. Hence, the electrical current that should be applied to recharge a 12 volt car battery will be much different than the current used to charge a cell phone battery.

Two principal types of battery charger technologies are used for converting the AC input in battery chargers:

Switch-mode: Switch-mode battery chargers are electronic devices that use a switching circuit to convert AC input at a very high frequency. They use predominantly solid-state components and do not require large transformers. These chargers are more compact, more energy efficient, more tolerant of input AC voltage fluctuation and slightly more expensive than those that use linear technology.

Linear: Linear battery chargers use an older technology with lower-efficiency transformers that generate more heat than switch-mode chargers. The charger is larger and heavier.

There are also several types of battery chargers: Timer Battery chargers, Intelligent Battery chargers, Fast Battery chargers, USB-based Battery chargers.

Timer chargers were the most common type for high-capacity Ni-Cd cells in the late 1990s for example (low-capacity consumer Ni-Cd cells were typically charged with a simple charger).

Often a timer charger and set of batteries could be bought as a bundle and the charger time was set to suit those batteries. If batteries of lower capacity were charged then they would be overcharged, and if batteries of higher capacity were charged they would be only partly charged. With the trend for battery technology to increase capacity year on year, an old timer charger would only partly charge the newer batteries.

An intelligent charger may monitor the battery's voltage, temperature and/or time under charge to determine the optimum charge current at that instant.

Fast chargers make use of control circuitry in the batteries being charged to rapidly charge the batteries without damaging the cells' elements. Some fast chargers, such as those made by Energizer, can fast-charge any NiMH battery even if it does not have the control circuit.

It's possible to use a USB cable as a power source for recharging batteries. Products based on this approach include chargers designed to charge standard NiMH cells, and custom NiMH batteries with built-in USB plugs and circuitry which eliminate the need for a separate charger.