Ive had this problem for months. I use a little battery tender to keep the battery charged.

When I bought my 2000 V6 mustang vert with 5 speed and a Jack Roush Kit, I didnt notice the battery.

In 4 days of it sitting, the battery was dead, not even a little click, so AAA told me my battery was too small. It really was. Got new battery and away I go.

4 days of it sitting,, the battery was dead. hummmmm. AAA, got a jump and away I go. Went back to Advanced Auto Parts, they put me in a bigger new battery. (No extra charge by the time I was done)

I finally got enough money to take it to who I was told is the best electrical car man around. Only thing he found was the radio had a small drain, but that would not cause the battery to die.

So here I am months later and its still the same thing. elec man told me I would just have to drive it more often. Well ok, but thats bs, it should be able to sit for weeks before a battery would be completly dead.

I decided I would start removing fuses, one by one, and on day 4 at some time in the future, I would know the problem. I looked up in the manual where the fuse box is, etc. Well, there seems to be 30 some fuses under the dash and under the hood.

I am open to great ideas, good ideas, not so good as well as impossible but give it a try ideas. sigh........................

 

Parasitic drain somewhere

 

Use an amp meter to measure the draw on the battery with the car off. Then remove (and leave out) each fuse, one at a time until you find the culprit. Follow your meter instructions for proper settings and such.

 

+1 .

 

How old is the battery! one thing i can say about battery's is that you can sometimes have a battery and it last 5-6 yrs. and i have bought new batterys that will not last 6 months or even a month!
It sounds like your battery has a dead cell. that will cause the battery to go dead in a day or so! If you have a battery that has the tops that you can refil the battery with, if you look inside you will see alot of panels sticking up. those are lead panels and they are very close together. after many months or yrs of road abuse the panels will weaken and fall over against the other next to it! When that occurs you will have a direct short in that cell. Now for a while you will not know it, but after time it will drain all the other five cells. that is why you have been chargeing it and it is still running down! Try this! start your car, and then take off the positive cable and hold it where it touches nothing! if the car stay's running then the alternator is chargeing the system. replace the battery. If the engine dies replace the alternator! that is how i check all my cars and trucks. or you can get a meter and see if it is putting out the right amount of amps.
But it sounds like to me that you have a dead cell in the battery. replace it with a new one! I got tired of replaceing batteries so i went and got the optima red top battery. it is for general use! and for 5 yrs now not a problem. It has six individual batters all conected together. But loose one and the others will not loose charge! they are very expensive but very well worh it! Hope this helps!!!!!

 

BTW, if you don't have a meter, they can be had pretty cheap at Harbor Freight. They don't stand up to abuse well but for your purposes it will do just fine.