I have a 4.6L V8 Explorer and yesterday while driving down the road, I go to stop at a stop sign and all of a sudden the battery light came on, the steering wheel locked up and I couldn't move the vehicle. After about 5 tries turning the key I was able to finally get to the side of the road. It happened again while slowing down at another stop sign on my way back home. I had the battery tested, it tested good. I then took the alternator to have it tested, and it tested good as well. Any ideas of what the issue could actually be?