There's a temperature sensor on the 12-V battery, that is used by the ECU to control the maximum charging current used, so as not to decrease the battery's life by charging it too rapidly at low temperatures.

Does anyone out there have a ScanGauge? I'm finding that my 12-V battery's voltage frequently drops below 12 V when my car is ON, but not READY. [I.e., two pushes of the Start button with your foot off the brake.] If you do have a ScanGauge, could you please read your 12-V battery's voltage under the above condition, say in the morning before you start the car after an overnight "sleep," and let me know the result? Normally, a properly charged 12-V battery's voltage should not drop below 12 V. As soon as my car is put in READY mode, my battery's voltage rises above 14 V, as should be the case. Does anyone know whether "glass separator" batteries behave differently? FYI, this is listed as a 48 amp-hour battery.

Stan