Gassing Battery and the Warning Signs of a potential Fire

I went down the companionway steps like so many times before, only this time something was a bit different.  There was this smell but I was not sure what it was.  I would describe it as somewhat sweet, but with a sour lingering smell, not real intrusive but certainly something that was noticeable.    I was chatting with Deb who was telling me about the progress she made sanding the wood trim, floor and shower grate while I was out of town.  She also mentioned that she had moved some things into a different storage locker in the galley and then suggested that I smell one of the cabinets because it had an odd smell to it.
Few snacks while the grill warmed up

I went to the one she suggested and sure enough it was that smell that I was smelling when first coming down onto the boat.  This is a cabinet along the port side mid ship behind the dinette seating and we keep mostly plates, dishes and pet supplies in there.  There is also the wash down pressure pump for the sea water spigot on deck but nothing that should have caused a foul odor.  Deb had told me that the CO2 alarm had gone off earlier that day and she figured it was from the sanding and the dust as it stopped in just a few minutes. The engine was not running ,the generator had not run, there weren’t any idling boats nearby and we didn’t have any kind of an open flame heater or anything else like that going, so I also agreed it was most likely just the sanding dust that affected it somehow.  Certainly the smell was stronger in this cabinet but not something that I could identify.  I lifted up the large floor hatch that goes down into the engine room and stuck my nose down there to see if it was any stronger down there.

Strange, but we let it go for now as we had dinner plans with boat neighbors where we were going to grill out and enjoy each others company.  Food and company was great.  We put out a spread of some snacks while we had some wine and grilled a bunch of veggies and then Salmon.  It is nice to have great boat neighbors.  Thanks Kevin & Betty of Lagniappe.

We had our dinner, which was lovely by the way, but when we went back down in the boat, that smell was just as noticeable if not more so.  Deb had gone to bed and while I was watching some TV and the CO2 alarm went off again.
As I sit here writing this I realize just how brain dead I must have been, because of what I did next and my logic for doing so.  I again knew that we didn’t have anything running that should be causing CO2 down below, so I chocked it up to the device reaching it’s end of life.  This particular model is disposable in that if the battery dies or the device does detect CO2 and the alarm goes off, you have to replace it  I read the back of the unit on how to stop the sound, which is essentially pulling up a safety/warning label and turning a small plastic slot about 20 degrees.  This permanently disables the device and requires the purchase of a new one. 

What I actually found was one of the 8D batteries in our house bank gassing out all vent caps.
I learned a lot about batteries this week.  I thought I had known quite a bit abut them in the past, but this really forced me to learn what is happening inside the case.  I started to put together my own reference manual a while back and I think I may just write an eBook.  I think I have enough material to go into detail about the chemistry behind battery discharging, charging and the potentially dangerous situations that can happen, such as in our case where the condition was causing an explosive gas to be formed in a compartment with a battery that was getting hotter and hotter.  Thankfully for us a spark was not formed, or there was not enough of this gas produced yet to have caused  an explosion.

One of the lessons learned for us however was that our inexpensive CO2 detector was somehow sensitive enough to have picked up the gassing condition from the shorted battery and had given us 2 early warning we ignored.  If you don’t have more than one CO2 detector on your boat, your gambling with your life.  Ours may have just saved ours this week.  There are marine grade CO2 detectors and even some that can have remote sensors for specific compartments. 
We have opted for simple ones that we can easily source and are inexpensive enough to keep spares on board.
Here are links to a few for your convenience. 

First Alert CO410 Battery Powered with display
Here is one that can have the battery replaced and has a display showing conditions
First Alert CO410 Battery Powered Carbon Monoxide Alarm with Digital Display

If you are invested in getting unit like the one on the right, you can click on it to bring up the Amazon site for it.

On our previous boat we had the First Alert style with the display and this was good to be able to see if they were still and working.

The picture to the left is a link to one that has a 10 year lithium battery in it and is sealed as well as tamper proof.  It is the style we had on board DreamChaser during this incident.

Kidde P3010-K-CO Battery Operated - CO2 and Smoke alarm with Photoelectric sensor

Be safe everyone.  This was a bit of a scary experience for us, not because there was some harrowing event, however when we thought about the possible dangers to this, it was a bit overwhelming.