Dumbest thing ever. I crossed jumper cables... uh oh!

Having a car battery blow up on you is quite an experience. I did it on an early 60's Pontiac and it knocked me into the ditch next to the car. Lucky for me I had my head shielded near the back of the hood, and since it was winter I had on lots of heavy clothes. The coat I was wearing looked like swiss cheese after we washed the acid out of it. The ringing in my ears lasted for a day or so, and there was nothing left where the battery had been but a small pile of molten lead plates and the flat bottom of the battery case. They make jumper cables that have relays so that you can't hurt anything if you hook them up backwards.
Now I always make the last connection to a ground on the motor or the frame, not to the battery, just to keep any sparks from flying across the top of the battery case. Glad you didn't have to learn the hard way. Later, Randy

 

Back in the mid 1970"s I lived in St.Louis. One subzero Newyear's weekend, my car wouldn't start and neither would my wife's. I caught a ride to the boss's shop and loaded a gas generator into the shop truck. Drove home &
I hooked up the cables carefully as always and let the generator run a bit, the car would not crank. I wiggled the cables and BANG, the battery blew apart, spraying my work coat and my face.
After cleaning myself and my acid speckeled jacket, I went to the other car and hooked the cables with extreem care and wiggled them into a good bite. After running the generator a good spell, I turned on the key and BANG went the second battery.
Had to go to the shop and get two new batteries. Later, guys at the shop swore the charger was ok. Wiggling the cables may have caused the first one, but the second time, I was sitting safely in the car and only turned the key on. Still wonder about that.
Safety first. Always put the "ground" to the block or frame, not the post & get away just in case it goes BOOM anyway.