Over the weekend, I had my old yet still useful 2006 MacBook Pro do some CPU intensive work unattended while I was enjoying my lunch. Not halfway through my pastrami sandwich, I hear a popping noise from the pantry where I had left the notebook running with its Apple charger connected. The notebook, still running, had been pushed up and off its stand because its Apple battery (a removable one, model A1175) had given up the ghost, breaking its case with some of its cells expanding to three times their normal width.
I immediately disconnected the changer from the notebook and unplugged it from the wall in fear that it may have been the culprit. The charger was at a normal temperature, but the battery was very hot.
While the notebook and its battery were no longer under the one year warranty, I feel that even when a warranty expires the product should not become a safety hazard. Perhaps I should be glad that I was in the next room and not out for an hour running an errand then coming home to a pile of ashes.
I'd like to send the battery back to Apple for a replacement in exchange for me forgiving them for bad design/bad manufacturing. But the US Postal Service refuses to ship a damaged lithium ion battery.
What is amazing is that, if it truly is the original battery that came with the computer, that you had not changed it out for a new one. I can't imagine that you were getting a lot of running time from that battery as it being 9 years old. It is unfortunate that the battery exploded though. I don't think I would have expected that either but then again I would have changed out the battery long before 9 years. Checking the battery status is something everyone should do periodically.