Battery issue, need help Options

[k-weaver]

So within the past week I have noticed that my windows were going up slower, my headlights would dim more when music was on, and my sun roof was VERY slow. This morning I started my car but it sounded as if the battery was pretty much depleted. I got the very slow errr-errr-errr before it turned over. I drove it like normal (left the stereo off) until I got to my destination. While the car was on I rollled up the windows and they went up like normal. I turned the car off and back on, started no problem.

So to me it sounds as if the battery is loosing its charge fairly quickly as it is sitting (overnight). I know that there is a way to "check the water level" of the battery but am not sure if all batteries have this capability to do this? From what I read online, there are sealed and unsealed batteries? So if mine is sealed (I think it is) is there any way to check and or refill the water level if this could be the problem?

Im gonna go out to the car now and check it out a little more. I will hopefully post some pics of the battery so you guys can see it. Also, there should be a date on the battery right? To tell how old it is? I have only had the car for 2 years but I don't know how long the battery had actually been in the car.

Also, I replaced the altenator about a year and a half ago, I don't think it is this because the altenator appears to be charging the battery. Its just when the car is sitting when it seems to be "dying". Keep in mind that it has yet to die on me, I just have a feeling that it will soon.