Thanks, I'll try adding the capacitor.

By VREF, you mean pin 5?
Should I connect it to the 5 Volt rail?
I imagine the 5 Volt power supply should be stable since it is now powered from the 7805.

Do I need to do anything to tell the pic that I'm providing the + 5 Volt reference voltage?



The red wire currently connects the battery to the ADC pin.
Cheers, Art.