Everytime a conventional automotive battery gets drained down, you cut its remaining life in half, so although the battery might look new if you have killed it a couple of times it may be shot. Deep cycle and Optima type batteries are the exception here.

All that said, if a new or good condition battery is draining down in a week, then there is a current draw on your car, from something electrical being left on. It could be something a simple as a dome light stuck on in the hatch area, or a warning light.

It could also be a mis-wired aftermarket part, such as a gauge or stereo or alarm.

Once you get a good battery in the car you should check out the system for a current draw, using a digital multi-meter (only about $25-$35 for a cheap one at your local Radio Shack)

 

I just had the same problem 2 months ago. Get a multimeter and check to see if your alternator is pushing enough volts. On my car I found the wire coming from the alternator was rusted almost in half. It was hidden under the rubber boot. I run a 1000 watt amp and have had no problems since. Hope this helps.

 

check your alt.....................

 

I'm pretty sure your altnator is fine. the problem is somehow you have a wire that is grounding or you have a component that is causing a huge parasitic drain on your battery that running the engine a couple days a week for 5 mins isnt enough for the battery to recharge.