I need some advise on the voltage divider network. I need to monitor the voltage for a 6V Lead Acid battery. I am planning to power my PIC using a suitable voltage regulator. I want such a regulator which is widely available and can provide a fixed voltage to PIC upto until the battery voltage voltage drops to 4.5-4.8V and PIC can monitor the decreasing the supply voltage through a voltage divider.

I also want to know what is MAX resistance values I can use to reduce the current drain.
Thanks