CO detector saved me -- with no CO present

[LeighWebber]

A couple of years ago I installed a Webasto diesel forced air heater. Wonderful unit -- works flawlessly. Last month, I replaced my ancient and failed Xantrex battery charger with a the Abso AC1260. I chose that unit because it supports three battery banks. I have a brand new house bank with 510 AH deep cycle AGM batteries, and an aging starter battery (flooded, maintenance free). At first, I didn't have a cable to connect the starter battery to the Abso, so I ordered one.

The outside temp last evening was about 55, headed down to about 45 overnight. I came onboard and flashed up the Webasto. Nice. Later in the evening I finished my charger installation by connecting up the starter battery on the charger's Channel 2. The starter battery was really run down (separate long story) -- only had about 8 volts in it. But I hoped the ABSO would bring it back to life. I could see the charger cycling on and off to coax the starter battery up to a reasonable voltage, then after an hour or so it kicked in and began pumping 25 amps or so to it.

I went to bed at about 10 pm. At around 1 am I was awoken by my CO detector. I have two of them -- one up by the V berth, and one in the main saloon. The former triggered first, followed shortly by the latter. I suspected a wind from astern was blowing exhaust fumes into the boat, so I shut off the Webasto, opened all the hatches, and turned on the three fans in my boat (my cheap air conditioning system). I watched the CO levels start to go down, and when the detectors stopped chirping, I hauled out my cold weather sleeping bag and crawled in. I would check for the source of CO in the morning. To be safe, I left all the hatches open.

In the morning, CO levels were zero. I closed the hatches, and made breakfast. About a half hour later, the CO detectors went off again. WTF! The Webasto had remained shut off, so it couldn't be the source. I checked up top to see if some huge motorboat had parked with its exhaust pointing at me, but nothing. Beautiful, fresh air morning. In the boat, however, I smelled something -- couldn't put my finger on it. I opened all the hatches again, turned on the fans, and cleared the CO levels down to near zero again.

Then my brain kicked in. The charger. I opened my engine compartment hatch and looked at the starter battery. Copious volumes of white smoke were pouring out of the thing! I opened every hatch, unplugged shore power, and got off the boat. An hour later I returned. The smoking had stopped, the funny smell was gone, and the CO detectors were quiet.

I don't deserve to be alive. I failed to check that starter battery as the ABSO began pouring on the amps. I think it was so badly sulfated that the heavy current and charging voltages caused it to emit hydrogen gas PLUS hydrogen sulfide gas. What saved me was my pair of inexpensive CO detectors. They triggered on the hydrogen sulfide, I think. Even though I failed to shut off the charger at 1 am, with all the hatches open and the fans running, the bad gas was cleared. When I closed the hatches in the morning, the gas built up again, and the CO detectors went off.

I had no idea that a CO detector could do this. These were NOT the "dual gas" models (propane + CO). I have separate propane detectors, and they were silent.

Lessons. First, make sure you have a couple of CO detectors even if your boat has no heating system of any kind. Second, don't connect a powerful charger to a failed battery. Third, when you reconfigure your charging setup, monitor the charging voltage and current for the first several hours to make sure everything is operating as it should. Fourth, when your batteries have been deeply discharged, watch them as they charge and stop everything if you see any gassing, bubbling, overheating, etc.