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How Does a Battery Charger Work?
Batteries work because of the electrochemistry between an anode/negative terminal and a cathode/positive terminal. Some battery chemistries have the property of being chargeable, so that when electrical current is fed into them, the electrochemical discharge reaction reverses itself and the battery "recharges."
Only some batteries have the chemistry and construction features that all them to be charged. Also, due to varying battery designs and chemistry, a given battery can only handle a certain voltage or amount of current. For example, the current fed into a lead-acid car battery would be very different from that of a lithium ion mobile phone battery.
The most common type of charging device is the simple charger. Drawing electric current from a wall outlet, this provides either a constant voltage or constant current and will continue to feed it into the battery until unplugged. Usually a transformer of some kind is involved to convert the voltage. For example, North American wall outlets work on the 110-volt standard, which is inappropriate if directly applied to a 12-volt battery.
Most charging devices work on this model. They are cheap, but because they never stop feeding in electricity at a set rate and do not stop until unplugged from their power source, they can damage batteries with overcharging if left unattended.
Trickle charging is a variant of the simple charger in that it puts out a constant flow of electricity but at a very low rate. That rate is set to match the particular battery's decay or self-discharge rate. When the battery is completely recharged, the charging therefore continues only at the rate necessary to keep the battery charged and no more. This prevents overcharging and, therefore, degradation or damage to the battery, but makes the charging process very slow.
The USB bus on a computer is standardized with a 5-volt power output. Therefore, many computer accessories are designed to use USB outlets for battery charging. Excepting that it uses electricity drawn from a computer instead of directly from a wall outlet, it is similar to other charging methods.
These chargers monitor either the time spent recharging, the temperature of the battery or the battery's voltage to determine when to autonomously terminate charging. This protects batteries from damage or degradation due to overcharging. Intelligent charging is becoming a popular charging feature for devices that use lithium ion batteries, as these are relatively expensive and suffer more degradation from overcharging than some other battery types.
NiMH Battery Charger Instructions:
There are quite a few options available when choosing a NiMH battery charger. Consider how many batteries the charger can charge at one time. Some can charge up to 10 AA or AAA batteries at a time, while other chargers can only charge two AA or AAA batteries at a time. How long the charger takes to fully charge batteries is another consideration. Some supposed "quick chargers" can actually take up to six hours to fully charge batteries, while other models can fully charge your batteries in 90 minutes.
Be sure you understand the manufacturer's instructions before charging your NiMH batteries. The risk of serious danger is low, but there is a possibility that your battery charger could overheat if it is not used properly.
To use your NiMH battery charger, begin by plugging it into an ordinary wall outlet. If your charger is equipped with multiple charging settings, select the setting and insert the NiMH batteries into the charger, being sure to observe the correct polarity of the batteries. When the light on your NiMH battery charger changes from red to green, your batteries are fully charged and ready for use.
NiMH batteries can be recharged and used multiple times. These batteries are easy to charge at home with an NiMH battery charger. Learning to use the charger is simple and can be done in just a few minutes.