Voltage spike & ABS/Battery light on...

Well I was driving home the other night from work, and as I pulled into the parking garage, my battery and abs lights came on, and had my voltage spike completely to the right on the guage. No biggie, I thought, cuz as I backed into my spot, everything went back to normal..

However, I got in it yesterday to head back to work, and the battery is dead.. I've searched through the threads, but couldn't find anything like it. Any suggestions? I'm really not sure where to start, though the abs/battery lights are throwing me off. I haven't had any problems in the past, everything running just fine. Engine is basically stock, aside from cai...

I'll start there.. But aside from having the alternator tested, anything else anyone can think of? It's left me really stumped, like maybe a fuse blew, or a relay went out.. I'm not too savy on the electrical system..