Battery light comes on and off and when its on the battery is drained.

Start by taking battery to auto store who will charge than test it. If its 3 or 4 years old it could b bad. Start simple. Many auto parts store will do it for free

We got a new battery, changed the terminals, and replaced the ground from battery to engine. We thought headlights were affected but we replaced them too. Fuses under the dash 2 of the 7.5 ones on the far left are out and the ac fuse keeps blowing( the ac used to blow hot air but now its not blowing at all) Any ideas?

I got the battery from walmart and it brand spanking new. So we changed the battery ground that connects to the alternator, the battery light would go on and off. Sometimes, the light would be lit on the dadh, but it seemed to be real dim, so we revved the engine in neutral and the dadhlight got brighter and then would turn off. This was interesting to me. Since im new to this, what am i missing?