CO alarm and unusual battery condition

[LiftyK]

I got to the boat last night to find the carbon monoxide alarm beeping. It showed a value of 125 and ok battery. Removing it from the boat stopped the alarm so I think the detector was ok. I disabled the alarm, closed the forepeak door, opened the fore peak hatch and went to sleep in the forepeak.

This morning I noticed that our shore power, which had been connected for the previous five days, was charging the service battery at 5A. Turning off the battery isolator, it continued to charge the battery at 5A. Disconnecting shore power leaves the battery at 11.1 volts. Upon inspection of the battery (standard lead acid) it doesn’t look distorted or different to usual but it is warm to touch.

The battery is in a cockpit locker and there is an air passage to the main cabin where the CO detector is located. The battery is seven years old, Banner brand. I will replace the battery this morning.

Could battery failure have caused the CO alarm to trigger?

Is instant death of a battery a common thing? It was fine a week ago.

 

[dankilb]

Could battery failure have caused the CO alarm to trigger?

Is instant death of a battery a common thing? It was fine a week ago.

Yes and yes, in my limited experience. Someone else will no doubt explain why! 7 years isn’t bad going for a boat battery.

 

[Momac]

I have known batteries to suddenly die . And I have heard of CO alarms detecting battery gas .

 

[Irish Rover]

Had the same a few years ago - CO detector picking up hydrogen gas from the dud battery.

 

[vyv_cox]

I had an article in YM on this not long ago. Most CO detectors will also alarm when detecting hydrogen. Battery failure during charging will release hydrogen.

 

[Biggles Wader]

Worth checking the battery charger too. Overcharging will cause a good battery to fail which rapidly becomes expensive if you have to keep replacing them.

 

[Momac]

A good point.
I replaced my battery charger last year - not as expensive as I had imagined . Example below - I have the three output version

 

[Boater Sam]

A failing battery on charge will also emit poisonous hydrogen sulphide gas which will trigger a CO alarm. That gas will also cause extensive corrosion of several metals in the boat.

I bought the same charger last week for £120on ebay. He accepted my offer. Victron Energy Blue Smart IP22 Charger 12/30(1) 230V CEE (BPC1230417002) | eBay

 

[LiftyK]

All very good to know. Thank you and much appreciated. In my case there was no smell from the failed battery. I’m really pleased the carbon monoxide detector helped prevent a larger problem by detecting not just carbon monoxide.

I purchased a replacement battery at 9am and was on my way shortly afterwards. Now at my destination for today, the new battery is taking current as it should so my ‘current’ charger seems ok. It is an ancient combined charger and mains supply. I dream of a nice Victron charger and as soon as the current charger fails I will definitely fit one of those.

Thanks again for all your comments - most informative.

 

[TNLI]

First of all make sure you have several voltage readouts around the boat. I have one analogue voltmeter as part of the engine panel, and two more digital ones built into switch panels in the wheelhouse and forward survivors cabin. That way if any of the regulators fail, it should be obvious. Top of the list for potential over voltage incidents is TWC or other intelligent chargers, like the BMC fitted inside the battery case of a Lithium battery.
A battery bay should be well vented even with sealed batteries, as Hydrogen is potentially explosive when mixed with air. Very few alternators, bilge pumps or switches are gas proof, (Rated as waterproof is probably OK),
Secondly I've never heard of a sealed Lead acid battery being so seriously overcharged the blow off vent cap fitted to all major brand ones produces enough gas to set off a detector. Hydrogen heads for the roof very directly, so if the detector is not directly above the battery bay, it will not go off disturbing your beauty sleep. I have had a CO and gas alarm go off for petrol fumes from a nearby outboard, and solvents from a leaking tin of paint. They also go off when the detector head gets wet.

OFF TOPIC WARNING!
Anyone know who is selling or doing Hydrogen gas burner head conversions. I did find some plans for use in a machine shop, but no real kosher companies based in Blighty.

 

[Northern Star]

I had my CO alarm go off too when one of my old 120ah Varta black batteries was on it's way out and it was confirmed that the detector had been triggered by hydrogen from the battery.

I now have new sealed Varta pro leisure batteries on board but as you say it is good to know that the CO alarm has more than one use for protecting us whilst on board.