Pat Buckley-Jones and his wife Ruth share the lessons they learned after battery gas from an overcharged battery filled their boat

Eight years ago, in 2013, my wife Ruth and I sailed Alandia, our Midget 31 yacht from Greenock on the Clyde to Lanzarote in the Canary Islands, writes Pat Buckley-Jones.

We intended to stay for the winter before sailing home.

When we had been there for a few weeks, we realised that keeping Alandia in the Canaries made a lot of sense and we have yet to sail her back to Scotland.

Usually we are fortunate to be able to make frequent visits to our boat but even so, one issue we have encountered is reduction of battery charge while we are away.

Keeping batteries charged is a challenge. We have two maintenance-free, sealed lead acid batteries, a 105A house and an 80A starter.

Despite the battery monitor showing the batteries ‘almost full’, the charger was busily boiling the damage battery. Credit: Pat Buckley-Jones

Occasionally on our return after a spell away we have found the batteries to be low on charge.

For safety reasons, marinas rightly discourage owners from leaving boats connected to shore power, so chargers cannot be used.

Noise from a wind generator will annoy other berth holders, so ours is disabled when we’re away. We have no solar power generation.

In late October 2020 we flew out to Alandia. Due to lockdown, she had been left unattended for nine months.

When we went on board, I checked the digital battery monitor connected to the house battery.

The reading was 1%, almost totally flat, so I assumed the starter battery would be the same.

No great problem, I thought. Alandia is fitted with a so-called ‘intelligent’ charger. My understanding was that such a charger will never overcharge a battery.

Crisis averted

I connected the shore power and the charger went to work. After 24 hours, the house battery was showing 90% on the monitor.

As ever, the charger remained connected to replenish normal use and all seemed well. About five days after we arrived, we were getting ready to go to bed.

As we closed up the companionway for the night we became aware of an unusual smell, a bit like hessian sacking.

Our neighbour in the marina lives aboard her boat and she often uses joss sticks or exotic oils.

The couple predominately sail Alandia in the Canaries. Credit: Pat Buckley-Jones

We thought perhaps the unusual smell was coming from her boat and so we went off to bed.

As I was drifting off to sleep, I continued to wonder what the smell could be.

I decided to check the batteries. Just as well that I did.

When I opened the battery compartment in the spare cabin, the smell was much stronger. I could hear the fluid in the starter battery boiling.

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The battery was swollen and it was extremely hot to touch.

The smell was clearly coming from the hot battery so I immediately switched off the charger.

Next, I went to search the internet to find some information about the smell coming from the battery.

I learned that it was hydrogen sulphide gas (H2S) – highly toxic, highly flammable and heavier than air.

We’d been about to go to sleep in a boat steadily filling up with battery gas that could kill us. I disconnected the battery and we went out into the fresh air.

The swollen, dangerous battery after removal. Credit: Pat Buckley-Jones

A little later, I went back into the boat and used the carry handle to lift the battery out onto the pontoon. On reflection, I’m not sure of the wisdom of that idea.

Some fluid splashed onto my foot but getting the battery outside seemed right at the time. I then aired the boat to get rid of the battery gas.

In the following days, l learned of four other boats in the marina that had experienced gassing batteries.

In a couple of cases, carbon monoxide alarms had activated.

On one boat, I was telling my story to a friend when he said his carbon monoxide (CO) alarm had been sounding that day.

We checked his battery. It was hot and apparently releasing toxic battery gas.

Learning about the risks of battery gas

I’ve since researched the activation of CO alarms by gassing batteries and find it to be quite common.

There are many instances of lead-acid batteries being charged in domestic garages activating domestic CO alarms.

However, not all CO alarms detect H2S. I had heard that a gassing battery smells of rotten eggs.

If I had smelt that initially, I may have realised that I had a battery problem.

The couple feel reassured now the new batteries are safely in place. Credit: Pat Buckley-Jones

Because I hadn’t smelt the sulphurous smell of rotten eggs, I initially took no action.

I’ve since learned that one of the insidious effects of H2S is to alter or desensitise a person’s sense of smell.

Perhaps that explains why I thought I could smell hessian.

I had believed that using an intelligent charger would prevent any risk of the batteries being overcharged.

I was mistaken. I’ve learned that when a lead acid battery has gone flat, or even below 50% capacity, it will suffer internal damage. It loses its ability to accept a full charge.

Pat Buckley-Jones, 59, is retired following a career in the Scottish Police Service. He has sailed since his early twenties on the Scottish coast and charters. Pat’s wife, Ruth is also retired after a career in psychiatric nursing. They spent much of their time with the sailing community in and around the Canary Islands Credit: Pat Buckley-Jones

However, the ‘intelligent’ charger does not realise this and simply keeps on charging.

After five days of being charged, our starter battery was boiling.

The presence of toxic flammable gas in our boat could so easily have cost us our lives or led to an explosion.

I hope that by drawing fellow readers’ attention to this issue, other sailors will be more aware of the potential danger from having a discharged lead acid battery aboard their boats.

Lessons Learned

• Avoid dropping below 50%: Lead acid batteries can be damaged if allowed to discharge below 50 per cent capacity.
• Take it seriously: A seriously discharged battery is potentially lethal. don’t rely on chargers Intelligent chargers do not identify that a lead acid battery is damaged and will continue to provide a charge leading to overheating and gassing.
• Understand the risks: The gas from an overheated lead acid battery can kill or ignite, and will collect in the boat’s hull.
• Install a H2S detector: H2S detectors are available. Some, but not all, CO alarms will detect the presence of hydrogen.
• Consider a solar option: A small capacity, regulated solar system could effectively and safely trickle-charge the batteries if your boat is left unattended for long periods.

Enjoyed reading Battery gas: A close shave for one sailing couple?

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