So I plugged in my new nearly full charge SLA battery (12 Ah) into a new charger designed for 12V batteries and within about 30 seconds the bottom blew out a corner, which I assume was the vent, out came about 15 drops worth of liquid which I assume is battery acid. This is an AGM Deep Cycle by the way.
This is my charger: Amstron 12V / 3A SLA Battery Charger - LC1-12-3A
I read online that the charger gave it too much power, but this charger is rated for this battery. What went wrong? I measured the battery the day before, brand new with no charging done at almost exactly 12 V.