Measuring parallel resistor without current
Your ADC is monitoring the battery voltage. Your temperature sensor just passes current from the battery to ground. The amount of current will vary with the temperature.



simulate this circuit &ndash; Schematic created using CircuitLab
Figure 1. Set R1 approximately equal to R3.
The output voltage will be given by \$ V_{out} = 3.3 \frac {R_3}{R_1 + R_3} \$.