Sunday, June 19, 2011

Whats that middle pin?

The popular Nokia BL5C battery(pic here) has 3 pins.One -ve,one +ve .. and the other one?
Mobile servicemen call it the "BSI" pin.BSI? They say its short for 'Battery Size Indicator'.Hmm,ok.Turns out,its a fixed resistor behind it,between the BSI pin and ground.The phone measures the resistance of the BSI - GND pins, and can determine what kind of battery is in.

The BSI GND Resistance for a normal BL5C comes out to 82.5k,and on a 4C to around 74.6k.Interesting.

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