Battery Size Resistor Measurement

The battery size, capacity is determined by measuring the voltage on the BSI pin on the battery pack when the battery is attached to the phone. The auxiliary channel 2 is used for this purpose. The BSI signal is pulled up on the base band using a 47 kohm resistor and the resistor inside the battery pack is reflecting the capacity of the battery. There are two special cases to be detected by the MCU. The first case is the Lithium battery. The Lithium battery has reserved values in the battery size table. Lithium type batteries are all the same from charging point of view. Lithium batteries are charged to a constant voltage and charging is aborted when the predefined voltage is reached. The Lithium battery capacity is a function of the battery voltage. The battery voltage drops linearly as the battery is discharged. The other case that has to be handled is the dummy battery. This battery is used for A/D converter field calibration at service centers and together with a defined voltage on the BTEMP pin on the battery pack to put the baseband into Local mode in production. Battery sizes below 143 mAh will be treated as dummy battery. The battery size A/D converter value can be calculated using the following formula:

where RSI is the value of the resistor inside the battery pack.

Battery Size and A/D Converter Value

Battery Type Battery pack resistor Capacity BSI volt. A/D conv value


Lithium type 1 standard battery

Lithium type 1 extended battery

Lithium type 2

<143 mAh0.07 400 mAh

900 mAh

400 mAh

DIY Battery Repair

DIY Battery Repair

You can now recondition your old batteries at home and bring them back to 100 percent of their working condition. This guide will enable you to revive All NiCd batteries regardless of brand and battery volt. It will give you the required information on how to re-energize and revive your NiCd batteries through the RVD process, charging method and charging guidelines.

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