You have the symptons of a parasite current. Which means there is a drain of 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.
These components include:
(1) Digital watches
(2) Radios tuned electronically by station memory and clock circuits (if the vehicle has them) you must make sure before disconnecting the battery, that you have the code of the audio system as in some vehicles when disconnecting the battery and reconnecting it again this access code is requested.
(3) Motor control computer (if equipped), through light leakage through the diodes
(4) The alternator through light leakage in diodes.
How to find the source of the leak
If there is a leak, it disables all the components which could generate energy consumption:
1.- Lights under the hood, Some lights under the hood are energized all the time and turn on by means of a mercury switch whenever the hood is opened. Unplug this switch.
2.- Light compartment (glove box). Make sure it is closed.
3.- Light trunk. The trunk should be closed as well as all the doors.
If after deactivating all these components, the battery leakage can keep the test lamp on, disconnect a fuse at the same time in the fuse box until the light of the test lamp turns off.
If the test lamp goes off after a specific fuse has been disconnected, the source of the leak is located on that particular circuit, as noted in the fuse box.
Check the circuit in question to determine what should be the leak.
Once the leak is found and corrected, check the light of the test lamp, it should not be on, if it is, it should be very dim.
In this case we can measure the amperage that is leaking by means of a multimeter since to some extent there are tolerances that are considered within the "normal" in a battery power leak.
Connect the multimeter in series between the negative terminal of the battery and the disconnected cable. The normal leakage of a battery is between 0.020 to 0.050 amps and any leak greater than 0.050 amperes must be located and corrected.
What should I do if the battery leakage exists even after all the fuses have been disconnected?
If all the fuses have been disconnected and the leak persists. the source of it must be between the battery and the fuse box. The most common sources of leakage under the hood include the following:
1.- The alternator. Disconnect the wires from the alternator and try again. If the test lamp goes out, the problem is defective diode (s) in the alternator
2.- The solenoid or gait relay or the wiring near its components, There is also a common source of battery leakage due to the high current flowing and heating the wire which can damage the wire itself or its isolation