· an interior light being left on
· a problem with the alarm
· an electrical fault etc.
The reason for it going flat needs to be caught as soon as possible to avoid permanent damage. Alternators can also fail which would mean the battery is not being charged sufficiently.
If you find your car is getting difficult to start, don't wait for a cold winter morning when its raining and you're in a hurry to find out! Call in now and get that battery checked out now!