You may have what is caled a "parasitic" load on the battery. That simply means something is drawing power from the battery after you have shut the car down. It is very easy to check. Try to do this test in a garage or somewhere besides bright sunlight. The light could be difficult to see outdoors.
Disconnect the Negative battery cable and insert a 12V test light between the end of the cable and the battery post. (You are going to make an electrical bridge with the test light) Make certain ALL power is turned off -ignition switch, radio, dome light, hood and trunk light, brake lights, etc. Remember, a parasitic load is something still turned ON when it shouldn't be.
If the test light is OFF---turn something ON (dome light, radio, ignition switch, etc.) to test the light. It should light up. If this works, you do NOT have a parasitic load. I would have the battery tested.
If the test light is ON ---you have a parasitic load. Start pulling fuses one at a time until the light goes out. Remember the door switch must be off if you are under the dash with the door open. When the light goes out you have found the circuit which is causing your problem. Repair and re-test. I hope this helps, good luck, David
The battery draw could also be coming from the alternator. They sometimes short out internally and still work. Just remove the large battery wire from the back of the alternator with the test light hooked up as explained above. If the test light goes out, get a new alternator.
