BSI Pin in Mobile Phone

Mobile phone battery requires only two pins for charging, then why there is a third pin? The question is definitely a curiosity generating one. 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.

BSI Pins in Mobile Phone

The Mobile phone battery has Lithium Ion chemistry. 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.

Lithium Ion Battery

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.