Is the ADC_DelSig_1_CountsTo_mVolts() actually trusted to be relatively accurate, assuming the VCC decreases as a battery drains?
Thanks for the advice.
It all depends on your selected reference voltage. Most precise would be an internal ref (buffered). Might require do divide with R/R network the battery voltage. Have a look into the specs of the ADC, the accuracy is defined over the whole voltage range.