Exactly.Jetdoc said:If the voltage regulator fails and allows the alternator to overcharge the battery it will create hydrogen gas. The battery will swell and some of the fumes will escape at the battery caps. It will smell like boiled eggs. You probably slightly bad connection at the terminal and when you tuned the key it made a tiny spark and BOOM!!!!!!!!
NEVER! NEVER! jump/boost off another car when you smell boiled eggs................
Check your connections at the battery and also at the starter.
I'm going to add to this.
We had one blow up in the shop a couple of months ago. It was a windy day and couldn't smell anything. It was on a Lexus LS400 and it blew all that plastic crap completly apart. Good thing nobody was standing near. It sounded like a gun going off.
Thats why they say to never jump your car with the cables directly connected to the battery. Always connect the ground cable last as well as on somthing other that the battery terminal itself.