Battery exploded ! Need explanation.

Ok, so my selonoid relay was out yesterday but I fixed it. Before I fixed it I hooked up my Chevy Silverado Napa 77O cca starting battery to the boat while my other one was charging.I used my truck battery while I was trying to start my boat with the relay/selonoid that was bad. I tried to start it about 20 times & gave up. I put the battery back in my truck & fixed my boat later & installed the boat battery back in. Today driving my truck with the Napa battery everthing was fine on the way to work. Later I went somewere & the battery was almost dead. It was unjumpable. Took it back to Napa & they said their tester said it was good & fully charged. They said my cable might be bad. I knew they were wrong. So me & my boss were putting the Napa battery back in & it still was bad. The lights would barely come on. I was turing the key & my boss wiggled the ground cable to see if the connection was bad & the battery exloded. It sounded like a pop & the top of the battery blew a 4 inch hole it the top. One of the caps flew off also. Parts flew 40 feet from my truck & my boss got acid on his arms. He is ok cause we had an ozarka water case in his car & none got on his face. Did the bad relay/selonoid energize the battery or pressurize it some how ? I will never mess with a battery now without caution. Sorry so long, Dan

Yeah I used to think nothing of those warnings myself but then I saw my dad pull off a charger wire and send a battery flying across the basement. Hydrogen goes boom, be careful all...

sulfated battery most likely, I only realy like to use AC/Delco batteries anyway most other brands are junk with the exception of about two other brands.

Once one explodes on you, you tend to approach batteries in a different way, I kept warning my nephew because you can smell the gases when charging or jumping, it exploded and scared the sh out of him, now i watch him and he will hook up the cables then plug the charger in, he is much more careful

I found this to be an interesting read on the topic: Exploding Batteries

On this topic, I noticed that the battery box on my 79 Tique dosent have ventalation. Just has a little hole with a hose it in that lets water from the bilge pool around the bottom of the battery. Do most of you have vented battery spots on your boats?

Wow, I thought those warnings were something that were never likely to happen. I guess eye protection, and standing back are good precautions. Some of these batteries are up under the bow, (on Malibus anyway). Pretty bad palce to have one blow up.

So, how do you avoid having one blow up, or is it sort of like a lottery, and when it's your time, it your time?

I've often used the spark test to see how much juice there was. I guess not a good idea.

Pete, I resent the remark to Billy Bobs Grandfather.You could have used some other name sake..............billy[ boat dr]

Pete, just a stab at you , no offense taken.
The Reverend Jesse and Al Sharpton are looking for a shot on late nite TV,Oh I forgot Billy Bob is WHITE..........ha ha