I had one exploded in my garage years ago.
Sent it back to Interstate so they could investigate, but never heard why.
Spark from the garage door opener opening must have lit hydrogen from it.
There were some fluorescent bulbs near it that got blasted when it went boom.
All the broken glass, plastic battery casing, and battery acid made a heck of a mess.
Luckily it didn't get my Expedition parked nearby back then.
Did do a number on the side of the Kennedy tool box's paint close by.
Took me a little bit to figure out what even happened.
I was outside the garage and used the opener control outside the door.
Heard boom as the door started raising.
Saw the mess once inside.
Initially thought the bulbs just exploded from temperature or something, it was winter.
Then started seeing all the plastic and acid as I was sweeping up.
Could see the direction and trajectory then put things together.
VERY glad no-one was near when it happened.
Heard that it could have been a pair of plates dislodged and shorted inside battery causing hydrogen discharge.
Then it made a cloud large enough to reach the spark from the door opener's electric motor.
Not 100% sure, but best I could figure after all these years.
it was a MESS !!
Used to have some pictures (sent those to Interstate too) but won't ever be able to find them.