How do you check the drainage of the battery if the altanator does work?

Answer 1

TAKE IT TO AUTO ZONE, THEY DO IT FOR FREE

Answeryou would require a special battery tester you are better off taking it to a garage to be tested check around some places does it for free

Heres an easy trick to try-

With the car off disconnect the negative battery terminal, now take an automotive bulb and two scrap wires, connect the wires to the neg- and pos+ of the bulb (a curcuit tester could work too), connect the light in between the negative terminal and the battery terminal. Now any current drain on the system will need to travel through the bulb to get to ground meaning if the bulb shines bright somthing is staying on and gobbling up battery juice, to find out what it is start pulling out the relays from the fuse box one by one, when you find the culprit the light will go out or get very dim, at that point replace the offending relay with a new one and the problem should be gone. A very, very dim small amount of light is normal as the cars clock and computer memory are constantly using a little bit of power.

I suggest going after the relays because they are often the cause of a battery drain, when they go bad they can stick in the on position and allow power to flow when the car is off. I had a problem with a bad relay myself, I could shut off the car but the daytime running lights and the heater fan would stay powered, replacing the relay fixed the problem.