Hey man,
Why, oh why, did the battery explode?
If the reason is due to the fact that the alternator was (is) overcharging, then the problem will reoccur.
If someone was attempting to jump start the jetta with the jumper cables improperly attatched, then this scenario could also occur.
So, WHAT HAPPENED?
Glad to se that noone was hurt or even BLINDED from this.
See 'ya in fishtown next time.
Spo out.