Yesterday after I brought car home, I was sitting in the garage and playing with the settings, then "battery low charge" warning showed up. I thought that the car was sitting on the lot (even though I drove it for an hour home) for a long time and battery was not fully charged. So I drove it today several times, and it starts just fine every time. Then I parked the car and was playing with the settings again, and the warning showed up again. What might be the problem?

the battery must be cooked...try a trickle charge overnight and if that doesn't work then go get it replaced on warranty

I think I will just go and get another one from the dealer.
It was sitting on the lot for 2 months before I bought it.
I wonder what caused battery drain, and will this happen again if I get new battery...?

You better contact your dealer and have then to check if there is a problem with the
electrical system.

Even if you car has been sitting for two months the battery should be recharged after
driving an our.

It is also possible that the battery drained out so bad that it got defected.