was charging my tractor battery ,when I turn key this happen
I was darn lucky

Not yet, no...

Happened to a friend of mine. He thought he may have have the charging leads hooked up backwards. Not sure though

everything was right ,top of battery hit the roof of build I was in ,14 foot side wall ,

Hydrogen gas produced from charging was ignited by a spark.Not that uncommon.

Vents on the battery clogged up or froze up? Any way not good!

Yes. all it takes is a loose terminal, sourse for spark and an unsealed battery. I turned the key to the start position and it sounded like a shotgun went off under the hood. This is why the correct technique for junp starts is to connect the positive sides then one of the negative on the batteries and the final ground to something metal away from the batteries in case there is a spark

Yep, had one blow up in my face. I was jumping it at the time. I am 99.99% sure I did not have them hooked up backwards.

I was at a lumber yard and had just bought some lumber when my truck wouldn't start. I felt the acid on my face and arms starting to burn and I said I needed some water and an employee took me into the bathroom there where I was able to wash off. After that they drove me to the parts store and I bought a new battery.

Worked on cars for many years. Learned this , luckily, the easy way. I was attaching jumper cables to a car to jump start it , small spark and crackel as the final connection was made. Then I noticed a few tiny sparks in the air near the battery caps. What I did not know at the time , there was a small fire I had ignited by making the last connection. A completely colorless flame almost invisible except for the few tiny random sparks in the flames. I backed up , was unsure of what was going on. Then the top of the battery exploded just like in the OP's picture. Luckily I had backed up , I didn't get hurt or any acid on me. Older batteries still have vent caps to allow excess gases like hydrogen escape. It also has a bit of a flame arrestor too , but may not work perfectly. Smaller batteries like for lawn tractors and such use older technologies to save costs.

Lesson learned , always connect the last connection with jumper cables to ground away from the battery like the engine block or a big piece of metal not the terminal of the battery. If it creates a spark like it does a lot , it is away from the gases exiting the battery.

In this case (OP's battery) it could be caused by a loose connection that upon putting power to the circuit , like starting the engine , all you need is a tiny , tiny spark and kaboom. Hydrogen is very , very quick to ignite.

happened to a local guy here while jump starting. his eye points forward, and the glass one points off to the side somewhat. very lucky he didn't lose both.

Yes I was helping a friend jump start his car.I was under the hood of his car making sure the jumper cables where contacting the battery .Turned away to check the same thing on my car and his battery blew up .I am talking less than 10 seconds after I turned away from his car. I was being looked out for because the battery was destroyed like yours More than 30 years ago now but I remember it like it was 30 seconds ago

It happened to buddy when we were teenagers. He was jumping another car, the hydrogen gas ignited and the battery exploded. He was blinded in one eye.

Glad you weren't hurt Trapper Dahlgren.

Have had more then one Blow up .Welding on semis to jumping old cars and tractors .

Yes my dad had it happen jump starting my 1948 willys jeep. Had to go to er to get plastic shards picked out of his face. Luckily he had his glasses on.
J

Again , I just want to pound this idea home. Safety first , last and always. Going through life with a accident that could have been easily prevented with knowledge is priceless. Cars/machinery/ farm equipment can kill or maim you very quickly.
ALLWAYS make your last connection to ground away from the ground terminal on the battery.

I knew of a friend who was jump starting a car leaning over the battery. His face was less than a foot away when the battery blew up. He was alone. He could not see with the acid in his eyes. He groped and felt his way to the front door of his house by feeling the small walkway. Groped his way to the kitchen sink. Flushed his eyes out with tons of water. Luckily he had no long term damage. Very lucky.

Very glad you were not hurt Trapper Dahlgren .

Doesn't happen every day, but if you work on cars long enough you eventually get to see one pop. Glad you were out of the way when it happened. It looks like it really scattered!
Joe

I have had a few blow like that. One in a boat that knocked me over board.

Worst one though was a very large batt. on utility vehicle at a federal prison. Like a HD golf cart truck type thing. That one exploded while moving close to 1000 lbs. of bird crap we had loaded on it. LOL Entire facility went into lock down because of the sound of the explosion. Tossed the driver right out of his seat onto the ground. I was told to stand still and not move toward the guy on the ground. Caused quite the scene in short order.

Yup

Just had one pop

Took out the head light assembly and windshield washer reservoir.

Very good thread. Hoping some of our younger less experienced members take heed.

Preventing even ONE Tman member from a lifelong injury is worth more than all of Tman past , present and future.

No offence, Paul.

Yes, keep that in mind this winter while jump starting.

Lady acted like she got upset the other day when I told her to get outta the way. And keep the kids outta the way too.