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Most cell phones chargers are not really chargers; they are only power adaptors that provide a power source for the charging circuitry which is almost always contained within the mobile phone. They are notoriously diverse, having a wide variety of DC connector-styles and voltages, most of which are not compatible with
other manufacturers’ phones or even different models of phones from a single manufacturer.
Cellphone chargers are nothing but AC to DC converters. They take an input of 220 volt AC and give an output voltage around 5Volt DC. Generally the output voltage of the chargers is in the range of 5 to 5.5 Volts DC, but some local make chargers give an output voltage beyond this level. As a user who is not bothered much about these technical details just connects the phone and checks whether the cellphone is getting charged or not, but in reality a cellphone which is exposed to conditions which are beyond the permissible limits might actually reduce the life of cellphone.
Different cell phones have different batteries and different voltage requirements. Usually though, the battery “goes dead” at about 0.8v less than its full voltage.
That is because if a battery goes too low it will be damaged and won’t recharge.To be completely accurate, when a battery is fully charged, it is usually about 0.5v higher than it is labelled. Universal Serial Bus specification provides for a five-volt power supply, it’s possible to use a USB cable as a power source for
recharging batteries. With 5V and 500mA of available current, the USB bus can charge a small single-cell Li-ion pack, but there is a danger of overloading the USB hub when attaching too many gadgets. Plugging in a charger that draws 500mA along with other devices will exceed the port’s current limit, leading to a voltage drop and a possible system failure. To prevent overload, some hosts include current-limiting circuits that shut down the supply when overdrawn.Another method is limiting the current of all attachments to 400mA to
reserve 100mA for housekeeping.


Most new batteries go through a formatting process during which the capacity gradually increases and reaches optimal performance at 100–200 cycles. After this mid-life point, the capacity gradually begins decreasing and the depth of discharge, operating temperatures and charging method govern the speed of capacity loss. The deeper the batteries are discharged and the warmer the ambient temperature is, the shorter the service life. The effect of temperature on the battery can be compared with a jug of milk, which stays fresh longer when refrigerated.Most portable batteries deliver between 300 and 500 full discharge/charge cycles.

Usually mobile phone battery require very low level DC voltage and current for charging, while our house hold wiring contains high level AC voltage of 220V and sinusoidal current. How is it possible for Chargers to overcome this issue? The technology that are involve are transformer and rectifier The transformer steps down the A.C voltage from 220V to low voltage around 5v. The rectifier converts the A.C voltage to a D.C. voltage
Basic Physics tells us that we need a higher voltage than the nominal output of a battery. For example your car 12 volt battery is recharged by the alternator (or free standing battery charger) at 14.7 volts. This is because of an effect that produces a ‘back emf’ during the charging cycle. If we choose to use a charger of 3.7 volts output then we would get only a partial charge on a 3.7 volt battery. The charging procedure is performed at constant voltage with current-limiting circuitry (i.e., charging with constant current until a voltage of 4.2 V is reached in the cell and continuing with a constant voltage applied until the current drops close to zero).


There are three USB specifications — USB 1.0, 2.0, and 3.0 — but we’ll be focusing on USB 2.0, as it’s by far the most common variant. We’ll point out where 1.0 and 3.0 are significantly different. The other important fact is that in any USB network, there is one host and one device. In almost every case, your PC is the host, and your smartphone/tablet/camera is the device. Power always flows from the host to the device, but data can flow in both directions.
OK, now the numbers. A USB socket has four pins and and a USB cable has four wires. The inside pins carry data (D+ and D-), and the outside pins provide a 5-volt power supply. In terms of actual current (milliamps or mA), there are three kinds of USB port dictated by the current specs: a standard downstream port, a charging downstream port, and a dedicated charging port. The first two can be found on your computer (and should be labelled as such), and the third kind applies to “dumb” wall chargers. In the USB 1.0 and 2.0 specs, a standard downstream port is capable of delivering up to 500mA (0.5A); in USB 3.0, it moves up to 900mA (0.9A). The charging downstream and dedicated charging ports provide up to 1500mA (1.5A).
Now, this is what the spec dictates, but in actual fact there are plenty of USB chargers that break these specs — mostly the wall-wart variety. Apple’s iPad charger, for example, provides 2.1A at 5V; Amazon’s Kindle Fire charger outputs 1.8; and car chargers can output anything from 1A to 2.1A.
There is a huge variance, then, between normal USB 2.0 ports rated at 500mA and dedicated charging ports which range all the way up to 2100mA. This leads to a rather important question: If you take a smartphone which came with a 900mA wall charger, and plug it into a 2100mA iPad charger, will it blow up?
In short, no: You can plug any USB device into any USB cable and into any USB port, and nothing will blow up — and in fact, using a more powerful charger should speed up battery charging. The longer answer is that the age of your device plays an important role, dictating both how fast it can be charged, and whether it can be charged using a wall charger at all. When cellphones are connected to USB ports of Laptops, the USB port can support a charging current of nearly 450mA without enumeration. Even with the hub case remains the same. We observed that maximum charging current with Windows Xp and Windows 7 operating system is 500mA without enumeration.

The fact that your plug fits into your charging port doesn’t mean you are using the right charger to charge your gadgets. Watch out!!!, this mistakes can be costly!!!
But why???
When replacing your charger, it is very important to get the one with the right voltage. The device may work with chargers with voltages that are close, but the effect is that it shortens the lifespan of the batteries being recharged. Some devices, however, works just fine due to tolerance of voltage variation. Meanwhile, some won’t just work at all. Now, here is the problem, how do you know this detail about your device? There is only one way to find out which category your device falls into, it is simply by getting the right voltage from the start.
Also, the ampere rating of your charger is very important. This is usually represented by notations like “1.0A” or “1000mA” on your chargers. In other words, while the voltage is a constant and should match, the
amperage is something that varies based on the devices need. A device will pull more amps when it is working hard than when it is not. The voltage will remain the same regardless. The amperage rating of a power supply is the maximum number of amps that it is able to provide if needed. Thus, as long as you replace your power supply with one that is capable of providing as much or more amps than the previous supply, you’ll be fine. If you replace the power supply for some reason with one that has a maximum amperage rating that is less than the previous and less than what your device actually requires, then you may end up with a burnt out or (at least) overheating power supply, and the device itself may not function, or may not do so well. Furthermore, most blackberry chargers comes in 700ma i.e., 0.7A, so using a charger of 1.5A i.e., 1500mA will fast charge the battery which may lead to battery damage if this is done often. For those who use their laptops to charge their mobile devices, they probably would have noticed that it takes a bit more time to get a full charge using this means. Most laptop USB ports are of USB 1.0 and USB 2.0 specifications and do not deliver more than 500mA (0.5A). This is a far cry from the recommended requirements for a lot of devices. Apple’s iPad charger provides 2.1A at 5V. Amazon’s Kindle Fire charger outputs 1.8A; My Galaxy Tab needs 5V/2A and my Samsung Note 1 needs 5V/1A.

Thanks for reading, hope u have learnt something new today?
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