The guy I bought it from says that he already replaced the alternator on it. Besides the steps it takes to get it started, the car runs great, as long as I take off the battery cables when I'm not driving it. :/

 

how long does it take to drain and how much do you drive the car?

 

If you have a multimeter you can measure the battery current when the car is off. Remove the negative cable from the battery and insert an ammeter. Positive (red) lead on the cable and negative (black) lead on the negative battery post. It shouldn't be more than about 5-10 milliamps. Mine is about 5 mA. Typical current drains are aftermarket radios and car alarms. It could be a bad starter solenoid or alt. First it helps to know the drain current.

 

Old batteries can do this too, as can batteries that have been discharged a lot.
Have the battery tested at a competent battery or auto store.
My 740 would drain the battery in a week if left to sit, now with a new battery, no problems!

Regards, Andrew.

 

I'm not sure yet. When I bought it the guy connected the cables before we drove it. I just don't want to connect and disconnect the cables every time I want to drive it.

I had a Kia before and the battery would die out if I didn't drive it every few days. I replaced the alternator when it changed to a few hours. I replaced the battery and it still did the same thing, lucky for me, I drove it every day!

 

I'm definitely going to do the multimeter thing. I'm pretty sure there's not an alarm system on it, but there is what looks to be a broken stock radio in it. I was going to replace it with something a little more up to date, do you recommend putting in a stock replacement? Or does it matter?

 

I got a cheapie Alpine AM/FM/CD from Crutchfield.com way better than the original. The Alpine panel was a little too bright at night so I rigged up an auto dimmer coming from the instrument lights, fuse 16.