Battery Temperature Measurement

The battery temperature is measured during charging. The BTEMP pin to the battery is pulled up on baseband by a 47 kohm resistor to logic supply voltage, 3.2V. The voltage on the BTEMP pin is a function of the battery pack temperature. Auxiliary A/D channel 3 is used for this purpose. Inside the battery pack there is a 47 kohm NTC resistor to ground. The A/D converter value can be calculated from the following formula:

A/D = RNTC/(RNTC+47 kohm)x1023

where RNTC is the value of the NTC resistor inside the battery pack.

The relationship between different battery temperature, BTEMP voltage and A/D converter values are shown in the table below. Battery temperature is measured from -56 to 76 Centigrade. ( 9 HEX to 383 HEX)

A/D Converter Values for Different Battery Temperatures

Bat. temp. NTC value BTEMP voltage A/D conv. value

-25

745.60 kW

2.96 V

962

0

164.96 kW

2.45 V

796

25

47 kW

1.58 V

512

50

16.26 kW

0.81 V

263

70

7.78 kW

0.45 V

145

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DIY Battery Repair

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