Replace a suspect battery immediately
And never use a Sears Die Hard battery
- it's a crappy battery with an average warranty (sounds good until you actually need to use the warranty, then they prorate it so you spend more on the replacement than a new reputable battery would cost from another source).
Anyway, a number of years ago, about 2 years after completely detailing my engine compartment (looked like it just rolled off the assembly line, sans 'OK' stamps), my battery exploded
I drove my car to work, and at lunch time went to run an errand. I got in, turned the key to 'start,' and "BANG!"
I immediately ducked down because I literally thought a gang shooting was taking place right outside my car. When there were no more gunshots, I slowly raised my head to peek about and see if it was safe, and I saw a bunch of smoke/vapor rising from the front right side of my hood. Another quick glance around to make sure there was no shooter, I got out and went to the front of my car and opened the hood to find my battery literally split in half, almost in 2 pieces, with battery acid ALL OVER the entire engine compartment!
If your battery is suspect, replace it!