Then something is on pulling power from the battery. Check all lights and relays.
Sounds like the alternator isn't working at all. Have it checked. Good Luck!!
I would suspect a bad alternator and battery, have them both checked at the parts store. A car with a fully charged battery and a bad alternator will run until the battery is drained and then quit.
Have you had the alternator tested? It may not be regulating the energy to the battery, causing it to drain
Well it maybe that the battery is to small for the truck or the alternator is bad
the diodes in the alternator have gone
Defective alternator.
altenator
I have heard the alternator does it,cold drains the battery too,if it's not started for awhile can kill it.
you have a dead short somewhere in electrical system. have the alternator checked even tho it is new.these have been known to b bad from the getgo. also have the starter motor taken out and checked by a good automotive electrician.these can have a short but still work check the voltage regulator.these are either built into alternator or are connected remotely the alternator and battery complete the electrical circuit, so if one is bad it will stop the vehicle when battery charge is gone Rocky_B - See my entry here for more things you might want to check: http://wiki.answers.com/Q/What_could_be_wrong_if_the_battery_light_stays_on_and_the_battery_still_runs_down_on_a_1996_windstar_after_installing_a_new_battery_and_alternator
Dead cell in the battery requiring a replacement battery or some light is on that is draining the battery. Can also be a stuck relay.
The main cause of battery drains is a bad electrical system. The electrical system is normally powered by the alternator and once the alternator goes bad the battery has a hard time holding a charge,
Alternator is defective or the battery has a dead cell and will not take a charge. Check the voltage at the battery with the engine running. You should have between 13.5-16 volts. Anything less and your alternator is bad.