2 points for you.
No , wait , that's at least a 3 pointer.

I was taught to connect the negative cable on the dead car to a ground instead of the negative terminal itself, but never knew why. I had no idea it was to prevent blowing the battery up. Good to know!

Overcharged a battery in my shop and cooked it. All the copper tags of the traps in my shop changed color. Lesson learned.

Yep. During an attempt to jump the battery. Luck was with me and I didn't get a scratch. The battery looked like the one pictured. Now I am like an old maid when hooking up a set of jumper cables. I ALWAYS turn my head!

Good practice. I learned to do this in a factory/industrial job. They spent a lot on training , it's a good thing. Whenever you are energizing /reenergizing something with a fair amount of electricity behind it and cutting the power with electrical panels/disconnects , at the last moment before you push the switch/ button , turn your head to the side. Things could arc/flash over. It takes less than a second for that to happen.

Current place I am working at , they look at me funny when I do this. The heck with them , I'm smarter , they can make jokes/ sneer all they want , I don't care.

Yes. 3 times over the years. I was lucky enough to be wearing my sunglasses on all three occasions. Not a fun deal! I cringe every time I put a set of jumpers on

Pawnee I only had it happen once but I agree I also cringe when ever I am using jumper cables to try to start another car!

I have jump started hundreds of batteries and never thought twice about it , I will never look at it the same way again !!! I was lucky

I would have driven to the ER....wow

Take off the negative cable first to avoid sparking is what I was told!

Spark possibly from a poor connection. Terminals look pretty dirty. Someone mention vents, all batteries have them. Even "sealed batteries". Anytime you charge or discharge a battery it "gasses", the closer to full charge or overcharged the more available gas. All it needs then is a spark, an arc from poor connection or even a broken plate/cell connector internally. We charged 20+ batteries in a series at work and all it takes is one to start a chain reaction. I have repaired posts on batteries with a mold, lead stick and a torch. A lost art, I was trained by a WWII vet that worked in Uncle Sam's motor pool. Man was amazing! RIP Bill. Key being to clear all the cells of gas. No gas no problem. Always wear eye protection, their not making new ones yet.

Slip

broken plate inside that caused a short,they corrode to a point they get thin and break off. wher two opposite plates touch.,dead short.

Had one blow up...after charging it ,in a 1970 Camaro SS.....what a sound ! Just that one in all the years I’ve been working on cars.

All 3 of mine were on irrigation wells. 2 while jumping and one that just went when I hit the start button. Most irrigation battery’s are a crotch level so it’s a wonderful experience!! Most farm wells have no protection against overcharging, so that’s one reason I have more experience with things going boom.

Always pull off the caps when charging and unhook the negative cable first. Charging in a closed space can be a bad situation because of gas build up.