I follow a BMW website that focuses on repair of BMWs. So, a guy posts a detailed description of how to change an alternator on a BMW X5 SUV. He says he didn't remove the battery cable first, because it's in the back and you have to remove the spare tire to get to it. So, he disconnected the cable and just tied it off with some string. It's still in the work area and he didn't even bother to put some tape on the big exposed ring terminal on the end. It's about half way down in the pics, after #7 in this thread:
It would be bad enough if the alternator terminal was easily accessible, etc. But this one you can't see well, it's underneath, all kinds of stuff nearby.
And now I have two idiots claiming that I'm a troll for pointing out that this is not only very bad practice, but dangerous. IMO, that pic, that procedure belongs in the book showing really, really, dumb things. But these guys can't grasp the fact that you have a cable the size of your finger running direct to the battery.