I have a 405 and the boat is new to us...about four months. A few weeks ago one of our marina neighbors called to say that an alarm was going off in our boat. I drove over and found two of the CO detectors sounding an alarm loud and clear. When I opened the windows in the boat, the alarms eventually quit. I was about to put new detectors in anyway, finished that task today. I had to go to the marina tonight to pick up some clothes and the new detectors were sounding again.

Now, there is nothing running on the boat except the refrigerator and the battery charger. Tonight I have read on line that a CO detector can also detect hydrogen. If that's true, seems that the only thing it could be is the battery system. Perhaps the battery charger is over charging, or there is a bad battery. Funny thing is, it seems to only happen at night.

Has anybody else had this issue and what was the fix?

Thanks for any opinions.