Problem with my Optima battery?

[notstock71]

Last night I put the Nova on the trickle charger because I was thinking about driving it to work today. The car has been sitting since last year. I have trickle charged it overnight before.

Anyways, I went out this morning and the battery is making a very faint sizzle sound. I unplugged the charger and the battery kept doing it. I couldn't look into it further, I was running late. I do not know if I have power or not.

Any ideas of what was going on? I am wondering if it overcharged (my charger is supposed to shut off when the battery is charged).