I had the opposite problem. Accessory belt started falling apart on the freeway, but everything was still running. I could tell because there was a loud snap sound and I could see pieces of the belt in my rear view mirror. I could also smell burning rubber. Got off, found a place to park, and popped the hood to find that there was only one rib still there and a bit on the loose side. Thought I might try limping to my destination, at which point I believe the belt was completely gone as I was parked downhill and partially blocking someone's driveway.
But I knew the belt was completely gone after a bunch of lights went on and the radio started failing. It was still about 4 blocks to my destination, where my wife really wanted to go. So for that period of time the battery was the only source of electricity powering the ignition. The battery was also about 7 years old (a JCI DieHard) that had also been through multiple jump starts due to my wife's tendency to leave the map lights on, although I left the headlights on myself one time. Found a local shop to do it, and they charged about $125 (replaced the A/C belt too since they were already there. At least the diagnostic fee was basically waived when the repair cost more. And I got a $25 Visa card. Not sure what they did with it, but I think they probably charged the battery, or at least jumped it.