I understand. You have the symptons of a parasite current. Which means there is a drain of the current, to find this we need to make several tests that i will try to explain the better i could.
Sometimes the battery of our car is discharged for no apparent reason being turned off, to check if there is any power leak we can do it with just a few simple steps.
If your car has a flat battery during the time it is off, for example during the night, we will start by disconnecting the negative terminal of the battery.
This to rule out that the car's battery is being discharged by some electrical device of the car.
If in the morning by connecting the negative terminal back to the battery, it kept its charge, undoubtedly we have an energy leak, this means that while both terminals remain connected to the battery the device that is leaking is discharging it, but when a terminal is disconnected, this causes the circuit to open and no electric current to flow.
How to Detect an Energy Leak if the battery is flat from the car when it is turned off
The battery leak test determines if any component or circuit in the vehicle is causing a battery leak when everything is turned off. This test is also known as a power-on test (IOD) or parasitic discharge test.
This test can be carried out whenever any of the following conditions exist:
1.- Whenever a battery is being flat when the car is off (and all its devices)
2.- Whenever the battery is suspected of leaking.
Procedure to detect the Energy Leak
Follow this procedure to perform the battery leak test using a test lamp:
1.- Make sure all lights, accessories and ignition are off.
2.- Check all the doors to make sure that the interior lights are off.
3.- Disconnect the negative cable from the battery.
4.- Connect the test lamp to the end of the cable disconnected from the battery and to the post of the same
5.- The test lamp should not light. If the lamp turns on, the battery may run out of charge in several hours.
Many electronic components consume a small amount of battery current continuously with the ignition off.