Using the right charger for your gadgets – phones – nigeria gas efficient cars


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.

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.

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?

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.

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.

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.

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.