Our CO detectors alarm, usually early in the morning (around 2 - 3 AM) but we do not think it is due to CO but rather the batteries associated with the inverter system. We have been working this problem for several months without success and are hoping someone else has had a similar issue and developed a solution. Here are the background facts:

- The boat is a 75' Skipperliner - 10 years old
- Engines and generator are relatively new diesels
- The hot water and cooking is propane
- We have 24 Trojan T-105 6 volt batteries on two inverters
- The CO detectors are Kidde KN-COB-B-LPM

I bought a Sensorcon CO meter and checked the engine compartment with the engines running, and, once beached, with the generator running and found no CO. I also checked the air around the hot water heaters and got 0 reading. The CO levels in the boat ran from 0 to 30 - 40. But the CO level in the bow compartment where the batteries are installed (which is sealed from the main boat living areas and compartments) reads up to 1,700. We know the meter responds to hydrogen, which is produced when the batteries are charging.

Based on the meter readings, and the fact that diesel generators produce very low levels of CO, we believe the cause of the CO detectors alarming is hydrogen gas from the batteries. How it gets into the boat is a bit of a mystery, as there is a bulkhead between the bow compartment and the rest of the boat, and we have sealed every possible opening where wires or cables come through the bulkhead into the main cabin area.

Has anyone had this issue? What did you do about it?