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Date: 22 May 2016. Carbon Monoxide Alarms and Batteries.

© janice142

I do not have to tell you I make mistakes. For proof positive of that read the Dealing with Drunks (tool locker and dinette table) article. This week I made another mistake, and a serious one at that. Honestly it was a compilation of errors. Usually the initial goof-up does not cause a catastrophic failure. The compounding is what ups a minor problem into a major one. The fault lies with me and I was fortunate that nothing serious occurred.

My initial mistake was in the placement of my carbon monoxide monitor. I have a battery powered one from Kidde. What I did not know is that they need to be high on the wall versus low.

For years mine was in the wrong place. I finally read the instructions and saw "up high on a wall outside of sleeping areas" is the recommendation. So I fixed that.

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Kidde Carbon Monoxide Detector, Battery Powered CO Alarm

Carbon monoxide is lighter than air. The alarm
needs to be placed above your breathing space.

When I learned this I moved the alarm to an appropriate place in my pilothouse. The pilothouse is also the highest cabin in the boat. Any fumes would gather there first.

I installed the CARBON MONOXIDE ALARM just forward of the pilothouse door on the port side.


Going aft the galley is one step down from the pilothouse. Heading to the bow, two steps down enters my forward cabin. The pilothouse is wonderful.  I installed the alarm and all was well. Two days later it started sounding off.

Because Iaam so smart (roll your eyes here) I did not think anything of it. I did take out the batteries to see if they needed replacement. The AA's tested at 1.3 volts. Fully charged they would be 1.5 volts. I assumed the batteries were getting old and the batteries in the alarm were what was causing the alarm to go off.

I had just this past week read of such an occurrence so there was some merit to the assumption. Minimally so. This was my second mistake.

What I failed to do was look in the bilge of Seaweed.
I did not check the house and start bank batteries.

Not checking my boat battery banks was my third error in the series. This mistake could have culminated Very Poorly. That I "knew better" does not help either.

I was complacent when I should have been vigilant.

The thing is this: On the first of each month I individually check each battery. I know the two in my start bank are old and beginning to fail. When I test them the voltage goes down further and faster than all the rest of the batts. I have been expecting the pair to fail any day now.

Well, guess what? With an alarm ringing I did not check the flipping batteries. Instead I removed the AA's from the alarm. I do not know what I was thinking. Well, actually I was not thinking. That is for certain. Please learn from my mistake!!!

Normally charging batteries will not make any alarms ring. Overcharging resulting in out-gassing will cause the alarm to alert. If I had opened the hatch and pinged (shot/tested) each battery with my Infrared thermometer I would have known immediately that one battery was hotter than the rest. The heat would have been yet another clue there was a problem.

When batteries are overcharged/out-gassing they heat up. That is a dangerous situation.

I was complacent because I check my batteries each month. I have heard that not a lot of boaters check their batts as often as I do. Mine are relatively easy to get to. Testing is a part of my monthly maintenance schedule.

Trust me when I say I should have immediately suspected a problem when that alarm went off. I knew that my start bank had flooded batteries circa 2010. They are at the end of their life cycle.

When shopping for these 12 volt meters, do not select the "mini" version. It is much smaller. 

The next morning I woke up to 12.2 on the voltage meter by my bunk. ARGH!!! When I saw that I knew the CO alarm was sounding for a reason. And I immediately knew which battery it was too. While I was busy kicking myself I solved the issue.


Mini-Lesson in Carbon Monoxide Alarms: The units do not just check for carbon monoxide. They also are designed to ring on the presence of a number of airborne particles dangerous to humans. That includes the out-gassing from batteries. When batts go bad they release a gas (out-gassing) that affects/sets off the alarms.

In essence the battery is overheating and a poisonous steam escapes. The out-gassing and battery acid inside the battery are two reasons why we should keep our batteries in boxes. Any fluids escaping the batteries cannot damage items in the boat when they are in a box.



Side Note: Aboard Seaweed I have a bunch of volt meters. Wherever I am there is within sight a display. They allow me to keep up with the state of my batteries.

I am aware of those fancy meters and monitoring systems for batteries. They are expensive.

These meters are less than $5 each from China. They work just fine.

With them I can tell how things are doing. It is not as precise as an electrical engineer may prefer however this is Good Enough.

Three things I did to abate any possible damage:

  1. I immediately shut off the solar panels so they would not be adding more power to the batteries.

  2. I isolated the bank. That means I shut off the switch that joins the start bank with the house bank. It is my policy to run all my batteries together.

  3. Then I disconnected the problem battery from the other start bank battery.

Aboard Seaweed I have two batteries in my start bank. Two are not needed because my engine is a small 18hp Kubota. The two batteries are from 2010. I knew they were going to fail. It was just a question of when. I wanted them isolated/separated from the rest of my better/newer batteries.

Replacing batteries is daunting. The financial burden is large, not counting having them placed in the boat.

Due to weight of the lead acid batteries I hire someone to place the batteries in my bilge. I can wire them myself.

I know that second battery will fail as both have had the same use cycles. The last one is still working so I will use it until it gives up the ghost. That is when both will be replaced. In the meantime I am saving my perfectly good money.

When the CO alarm rings next time I will
find out the reason why. No assumptions!


This is what my meter showed on the bad battery:

For those like me not so long ago, any reading below 12.0 is too low. A battery reading below 11.5 is considered dead. The likelihood of being able to recharge it is not good. My bad battery at 10.84 is *toast.

*Toast: Not recoverable. If told your battery is toast that means it won't work any more. The term is used most often in computer repair dens. "The hard-drive is toast" means the part has failed and data cannot be recovered.

Aboard Seaweed I keep close track of my battery voltage. When the numbers get below 12.3 I start shutting down the extraneous. I will not make more popcorn nor will I enjoy a movie marathon. Instead I will spend time reading on my Kindle.

It's a good life afloat, especially with a Kindle.


I made several errors.

  1. Initially the carbon monoxide alarm was placed incorrectly. It needs to be near the ceiling.

  2. When the alarm went off repeatedly I assumed it was the batteries inside the unit that were failing.

  3. I should have looked for the cause of the alarm rather than ignoring it. Because I check my boat batteries each month I was complacent.

  4. That won't happen again.

Alarms serve a purpose and I will definitely pay attention to mine. Just because I test a battery once a month does not mean it will last out the next thirty days. I knew I had two weak batteries so I should have immediately suspected a problem when the CO-alarm sounded.

Be smarter than I was. Really there are so many ways you can be smarter than I was this time.

Happy SAFE boating to you and yours. I will be here in the galley eating humble pie. Care to join me?

Do you have a CO alarm in your home?
Are your alarms in the right place?

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