While reinstalling my subs, I was tightening the bolt onto the positive terminal of the battery. The wrench touched some sheet metal and sparked bigtime. I immediately dropped the wrench, except it fell bridging the gap between the positive terminal and the sheet metal. The wrench instantly welded itself to the sheetmetal and turned bright red, lighting the plastic surrounding the battery and the battery cover on fire. Luckily I was able to grab a fire extinguisher and put it out quickly, since the wrench had melted through by then.
Totally my fault, but I'm glad so little was damaged. There really was nothing I could do to stop it once the wrench landed on the sheetmetal. I should have disconnected the battery's negative terminal, but when I first did that before attaching the positive, the alarm went off, so I reconnected it.
Oh well, I'm out for towing, new battery, probably some mounts or something, but all in all I am lucky as hell. Those battery cables are damn close to the fuel tank
When I came back out with the fire extinguisher, I half expected the rear end of the car to be engulfed with flames.
Lesson learned!