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Schematics of Nokia battery.

Information about Battery Size Indicator

Also known as[edit]

* Battery Status Indicator

  • Battery System Indicator
  • Battery Style Indicator
  • Sim Removal Indicator
  • Flash Programming Signal


There are some mobile phones, which has shorter BSI pin. It is because when the battery is being removed when the phone is turned on, the BSI circuit interrupts first, which tells the processor to shut down all communication to prevent damage.

What is BSI?[edit]

The battery block contains BSI resistor for battery identification. The BSI fixed resistor value indicates the chemistry and default capacity of a battery. Temperature and capacity information is needed for charge control (charging current and the voltage).

It is connected to resistor to GND. The phone measures the resistance of the BSI - GND connectors, and it can determine which kind of battery is in the phone.

Examples: Nokia NiMH batteries:

  • BMC-2 640mAH 3.3 kOhm
  • BMC-3 900mAH 5.6 kOhm

Nokia Li-Ion batteries:

  • BLB-2 650 mAH 68 kOhm
  • BLC-2 900 mAH 75 kOhm
  • BLS-2N ? mAh 50 kOhm

See also[edit]