Car not starting

What is your question?

My car keeps having an issue of not starting and its happened 3 times now. The first time it died it was after i parked and i tried to jump it off and it took a lot of effort but we got it started eventually and it died going down the road. I assumed it would be that battery and got it checked at autozone and they said it was dead. So I got a new one and the car ran for about 3 weeks and did the same thing again. I parked it and when I came back to it it wouldn't crank. Won't even make much of a sound unless it's hooked up to another car with jumper cables and then it sounds like it's trying to crank but just can't. I towed it to my mechanic and he said the terminal cable connector thing wasn't on there right and he put a new one on. 3 weeks after that I park it and I come back and it's dead. since I had warranty on the battery I went to autozone and got a new one and it cranked and drove it to my mechanic. My mechanic can't really figure out what's wrong with it.

What makes this problem better or worse?

The problem gets better when I put a new battery in it. One note before my mechanic fixed my cables I had code P0440 and after he fixed them it didn't come back on again until the day I drove it, parked, and died for the third time

How long has your 2009 Hyundai Santa Fe had this problem?

Like 10 weeks