Why Cellphone Explodes? Fact File 9

Rarely, but possible if a damaged battery is over charged.Improper maintenance and unnecessary charging may results in battery damage. The reasons for explosion may be a damaged battery, over charging, overheating, voltage spikes and lightning during charging etc. Mobile phone battery has Lithium Ion chemistry and is long lasting and maintenance free. Proper charging and discharging are necessary to maintain its life. If well maintained, the battery can be in top condition for more than three years. Over charging is the major cause of battery damage. It is better to charge the battery only when its charge indicator drops to 20% charge level. Unplug the charger after 1 hour when the charging process completes. Do not allow overnight charging. Also use a good charger that can give sufficient current for charging. The major cause of the battery explosion is gas accumulation inside the battery since there is no vent to release the gas. This occurs only when the battery deteriorates due to aging. The lithium battery has flat surface but the battery bulges out when the gas accumulates. A simple trick can be used to check this. Place the battery on an even surface and rotate. A good battery will not rotate while a bulged one will rotate. Replace this battery immediately. A word of Caution– don’t use cell phone while charging. Our head is valuable than the Cellphone. Let us see more about the Mobile phone battery.

The Li-ion battery has three components inside. These are Anode, Cathode and Electrolyte. The anode is made up of carbon and cathode is a metal oxide. The Anode is commonly made of Graphite. The metal oxide in the cathode may be Lithium cobalt oxide, lithium iron phosphate or lithium manganese oxide. The electrolyte is lithium salt dissolved in an organic solvent. It is a mixture of organic carbonates like ethylene carbonate or diethyl carbonate containing lithium ions. The sources of lithium ions are Anion salts like Lithium hexa fluorophosphates( LiPF6), Lithium hexa fluoro arsenate monohydrate(LiAsF6), Lithium perchlorate(LiClO4), Lithium tetrafluoro borate(LiBF4), Lithium triflate(LiCF3SO3) etc. Based on the anion salts used, the voltage, efficiency, life etc of lithium battery varies.

Three pins in Mobile battery

Mobile phone battery requires only two pins for charging but there is one more pin. The third pin called BSI pin performs very important functions and act as an interface between the Mobile phone and the Battery. When the battery is removed, without switching off the Mobile phone, the BSI circuit is first interrupted which convey the information to the processor to shut down all communications to prevent damage. To communicate with the BSI, the battery pack also has a BSI pin. BSI stands for Battery Status Indicator or Battery System Indicator.

In some Mobile Phone, the battery power connector has three pins and the battery also has three pins. These pins are Positive, Negative and BSI. The BSI pin in the Mobile phone performs important functions. The battery pack has three pin outs. The pins located at the ends are + Bat and – Bat pins to charge the battery from the adapter. The third pin is the shorter BSI pin usually present in the middle position. The battery block of the Mobile phone has a BSI resistor for identifying the battery pack placed in the phone.

The BSI fixed resistor value indicates the capacity and chemistry of battery. It also tells the phone processor about the temperature and charging voltage and current passing to the mobile phone. The BSI resistor connected to ground and the phone measures the resistance between the BSI and Ground and tells the processor about the type of battery inserted into the phone.


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