Apart form normal use of the battery, it is possible that the battery is getting old. Most types of rechargeable battery become less able to hold a charge as they age or may indeed have a finite number of times that they can be recharged. This will happen to phone batteries and to car batteries. When this happens you need a new battery and make sure that you dispose of the old battery properly (they contain chemicals that harm the environment).
Then either something is on draining the battery or the battery has a dead cell draining all the rest and must be replaced.
Your alternator is shot.
Either a short to power or a bad fan switch.
When replacing battery, when servicing some part of the engine, or when the vehicle is not going to be started for over one month.(keeps the radio memory from draining battery)
try disconnecting the battery
I had the same problem on my denaly it is a module in the dash for the heather. even if you turn the key off it is still on
what alarme is it find the wiring digram and remove the fuse
The battery has a dead cell and needs replacing or something is on pulling power from the battery.
It could be the voltage regulator.
Could be the life of the battery has expired or the charging system is faulty or the vehicle has a draw on the system killing the battery when not running. Drive the vehicle to your local auto parts store. They will test the battery and the charging system at no cost. Battery is bad or something is draining it. Most places that sell batteries can check it. With it charged, disconnect it and see if it holds a charge. If it does, something in the car is draining it. Dead cell in the battery or something is on drawing power from the battery.
Could be an older battery that can't hold a charge any longer Could be loose or corroded battery cables not supplying a sufficient charge from alternator Could be a weak alternator not charging battery Could be excessive parasytic load drain to battery ( a fully charged battery should be able to hold a charge for 21 days of inactivity) Could be a hidden accessory left on draining battery (i.e. trunk light, glove box light, etc.) Could be a defective voltage regulator not opening on engine shut down draining battery.
the alternator isn't charging as it shouldthe battery is bad and can't hold a charge any longeryou have an electric fault somewhere which is draining the battery.