The past two mornings I went to start the car and it was dead as a door nail. Nothing was left on to drain the battery, and I replaced the battery one year ago. I went to jump start it yesterday and the alarm started going off when I hooked the cables up. I then put the key in the door, locked and unlocked hoping that would reset the alarm. It seemed to do the trick and the car started right up. Why did this happen again this morning?

If an automatic transmission make sure it is fully in the Park position.

Have to do a Parasitic Current Drain Test, to find
the circuit with the fault,then component test items
in that circuit

You have a module,relay or other item, not timing out
or going to sleep

You can have failed switches in the doors,failed alternator
diodes,many things that can cause that

Even the Evap System, which on some cars, run tests while
your sleeping, can be at fault

Check for OBD Codes in all Modules, with professional scan tool,
then do the drain test, leaving the doors closed

If the battery is more than 3 years old, replace it

It could be a charging issue. But it could also be that something is draining the battery. To test the alternator you'll first have to charge the battery using a battery charger. Then follow this test.
http://ricksfreeautorepairadvice.com/test-an-alternator/

If the alternator passes, then conduct a battery drain test with this procedure
http://ricksfreeautorepairadvice.com/battery-dead-morning/
Battery dead in the morning Ricks Free Auto Repair Advice

Did you check the alternator? if it is faulty the car will drain all the power from the battery until it goes flat

2 things, not enought cold cranking amps, or while you where trying to start the car the brushs inside the starter caused a ark on the armature causing the starter not to be working at 100% option 1 have a drain test done or 2 replace the starter the drain test will show how much amps its taking to spin the starter if its pulling a high amount of amps/votage to spin the start then replace starter

I had the same thing this morning does anyone know is it bad starter ?

Remove positive battery terminal from battery & put a 12 volt test light in line between cable & battery post. As long as 12 volt light is illuminated, you have a draw. Start pulling & re-installing fuses, one at a time,until you see it dim or go out. If it goes out, you found your draw. If it dims, slight draw, such as radio memory etc. if all else fails, make sure you know where they all go, then pull them all, and start putting back one at a time. When light comes on bright, you found the circuit causing the draw.

battery is in the trunk

have you not left any load on overnight?..like park light or left the door partially open and the dome light would be left on?

have the battery recharge and the next night, make sure that no light would be left on the car.

if it would drain out again, have it recharged again, use it and on the night, make sure no light is left on the car, then remove the positive pole on the battery overnight.

the next morning, put the positive cable back and start the car.

if the car would start, then no problem with the battery, if the car would not start, then return the battery because it is defective.

tnx 4 using fixya,

drcool