Battery Charger
The types of battery chargers
A battery charger is used for re-charging re-chargeable batteries, by forcing a current through it, reversing the chemical changes that take place when the battery gets depleted. While charging a battery, the charge current depends on the battery technology and the capacity of the battery being charged. The re-charging current applied to a 12 volt automobile battery is very much different from the current applied to a NiCd battery.
When a charger is connected to a battery, current flows through the cells, which forces the current to reverse the chemical reaction of the battery cells, bringing the cells into charged conditions. This simple arrangement makes a battery charger inexpensive, but there exists a trade-off for quality. A charger in its simplest form would take longer to charge a battery, and at times may over charge the battery and ruin it. However, any charger would destroy a battery if left on charging longer than required.
In case of NICd batteries, the voltage of the cells gradually increases as they are being charged. The process continues till the battery gets fully charged. While charging, the output of the battery charger slowly increases, coming down when the battery is fully charged. This decrease in voltage indicates to an intelligent charger that the battery that charging of the battery is complete.
There are fast chargers available, which charges the battery rapidly without damaging the battery elements. These types of chargers would usually have a cooling fan, which is used for preventing the cells in the battery to over-heat. You can also get chargers which charges the battery over-night, if used with standard NiMH cells that do not have the special control circuitry. Some of the fast chargers, made by Energizer, are used to rapidly charge NiMH batteries even if it does not have the charge control circuit.
Pulse technology has also been used in a battery charger, where a pulse of current is fed to the battery. This is a DC pulse having a strict control on its rise time, shape, pulse width, frequency and amplitude. A charger designed with pulse technology can work with any type of battery, having any size, voltage, capacity, or battery chemistry. This would include automotive and valve-regulated batteries.
Universal serial Bus (USB) specifies a 5 volt power supply, which makes possible the use of a USB cable as a power source to charge batteries. Such products, based on this principle, can charge standard NiMH cells, and custom NiMH batteries with built-in USB plugs and circuitry which eliminate the need for a separate charger.
In choosing a battery charger you have several options that can be discouraging in making your selection. If you follow a few rules, you will be able to choose the right battery charger for you, for the battery type that you have, which will provide you with a top quality performance. The classic feature of a battery charger should be the one which can handle both, the NICd and NiMH batteries. A charger for NiMH battery works with NiCd cells, but not the other way round. These chargers usually work with AA or AAA batteries.
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