Thought I’d share a scary experience. I was jarred awake just prior to 5 AM by our aft carbon monoxide detector alarming. There was an odd pungent smell, and even odder sound. The sound was kind of like a cross between crackling and chattering high pitch. I quickly vented the boat, and started looking for the source of the smell and sound. I eliminated an oil filled electric heater, and eventually isolated the sound to my battery compartment. I found the starboard MK Deka 8A4D AGM battery quite hot, gassing, with visible rapid bubbling in the caps. I immediately shut off the charger, vacated the boat and gave the batteries a couple hours to cool down before removing any cables fearing a spark.
It was very fortunate that I was on the boat, and able to interrupt a thermal run-away of the AGM battery. While AGM battery manufacturers