Can AA lithium batteries be trusted on a boat?

[Gybe Ho]

I am buying too many alkaline AA batteries to keep electric candles and Christmas lights running.

 

After some Amazon research I was all set to order NiMH rechargeables until I found a review warning their nominal 1.2 volt technology means electric candles run a little dull, even with freshly recharged NiMH AAs, compared to regular 1.5v alkalines.

 

This led me onto the niche sector of AA batteries, namely 1.5v lithium rechargeables. None of the big names do lithium AAs, what is the reason?

 

Does any forum member happily coexist with 1.5v rechargable lithium AAs onboard?

[nicknorman]

10 hours ago, Gybe Ho said:

I am buying too many alkaline AA batteries to keep electric candles and Christmas lights running.

 

After some Amazon research I was all set to order NiMH rechargeables until I found a review warning their nominal 1.2 volt technology means electric candles run a little dull, even with freshly recharged NiMH AAs, compared to regular 1.5v alkalines.

 

This led me onto the niche sector of AA batteries, namely 1.5v lithium rechargeables. None of the big names do lithium AAs, what is the reason?

 

Does any forum member happily coexist with 1.5v rechargable lithium AAs onboard?

There is no such thing as a 1.5v rechargeable lithium cell, the chemistry can’t do it. The 1.5v AA batteries have 3.6v Li cells and boost/buck/bms circuit to convert between the cell voltage and the 1.5v output and give the usual protections. Probably the major manufacturers think this is too difficult and unreliable.
As to whether safe, you are into the area of exploding lithium polymer cells. Probably ok if the electronics hold up and you use the purpose designed charger, but I would want to charge them outside the boat.

[Jen-in-Wellies]

AA alkalines have a steeper voltage decline curve than NiMH. Alkalines can be at 1.2V long before they are flat, especially under load. NiMH stay at around 1.2V almost till the end. I use them for a couple of things needing AAs, including bike and caving lights, where brightness is much more important than in some decorative candles. They work fine and save a lot of cash over time, plus more eco friendly, with less waste. Use them in preference to disposable AAs now for everything except the CO alarms, which are safety critical and the destructions say to use alkaline cells. No reason to run the potential risks of Lithium chemistry where it isn't required.

[cheesegas]

As above, inside the lithium AAs is a little 3.7v li-ion NMC pouch cell and a DC-DC converter to get the output down to 1.5v.

 

Works well in theory, but there's not a lot of space inside for the electronics, and some don't have a low voltage disconnect. Fine for something like a torch, where you'd see it's getting dim and recharge, but for a candle which might be left on overnight by mistake, it's dangerous.

[JoeC]

My new boat insurance with GJW this year (only just renewed) states that if you have lithium batteries in the boat then you must have a lithium fire extinguisher. I don't remember it being in last years but have not double checked.

It makes no mention of small electrical lithium nor domestic lithium batteries nor the size of the extinguisher you need. Therefore, I will probably buy the smallest lithium fire extinguisher possible because if any battery decides to burst into flame, lithium or not, I am not hanging around!

[Russ T]

9 minutes ago, JoeC said:

It makes no mention of small electrical lithium nor domestic lithium batteries nor the size of the extinguisher you need. Therefore, I will probably buy the smallest lithium fire extinguisher possible because if any battery decides to burst into flame, lithium or not, I am not hanging around!

When I asked GJW the question, they replied:

 

Quote

With regard to your question of Fire Extinguishers, we do not recommend nor have a list, and would suggest that you contact the battery and/or fire extinguisher manufacturers for guidelines of the compatibility of the fire extinguisher that is specific to your installation.  

 

[cheesegas]

12 minutes ago, JoeC said:

My new boat insurance with GJW this year (only just renewed) states that if you have lithium batteries in the boat then you must have a lithium fire extinguisher. I don't remember it being in last years but have not double checked.

It makes no mention of small electrical lithium nor domestic lithium batteries nor the size of the extinguisher you need. Therefore, I will probably buy the smallest lithium fire extinguisher possible because if any battery decides to burst into flame, lithium or not, I am not hanging around!

There's a much higher risk of a small portable thing containing a lithium battery burning your boat down - power bank, camera battery etc. They contain li-ion NMC batteries which are more sensitive to over/under charge than LFPs, and can be bought very very cheaply in devices which may have poorly designed charging and protection circuitry. Super cheap things sometimes have re-used cells from old laptop batteries, which may be imbalanced and the BMS isn't smart enough to shut it off when this happens.

 

Also added to the risk is that people often charge them lying on a flammable thing like a sofa cushion or bed. One of the worst recent maritime disasters by death toll in the US was caused by a knockoff GoPro battery being charged on a sofa in a dive boat, which caused a fire that burned it to the waterline during the night.

[Alan de Enfield]

24 minutes ago, Russ T said:

When I asked GJW the question, they replied:

 

And for the 1st time my insurers have included a clause :

 

If Your Craft , tender or toys are fitted with Lithium- ion batteries they must be charged within daylight
hours , must not be left unattended whilst being charged and they must be used in accordance with the
manufacturers’ recommendations/instructions.

 

The underwriters are not some back-street fly-by-night company.

 

"Tokio Marine HCC is a trading name of HCC International Insurance Company plc, which is a member of the Tokio Marine HCC Group of Companies. HCC International Insurance Company plc is authorised by the Prudential Regulation Authority (PRA) and regulated by the UK Financial Conduct Authority (FCA) and the Prudential Regulation Authority. Registered in England and Wales No. 01575839 with registered office at 1 Aldgate, London EC3N 1RE.

Underwriters will provide insurance to the Insured during the period of insurance. It is agreed that this Schedule forms the legal document which gives evidence of and forms part of the Contract between the Insured and the Underwriters until the expiry of the insurance or unless and until replaced by any subsequent Schedule or Policy Endorsement. This schedule must be read in conjunction with your Policy booklet".

 

Financial strength

We’ve got the financial strength to keep you secure with some of the best financial ratings in the industry.  Our Gross Written Premium for 2024 was $7.9 Billion* and our headcount stands at 4,400** employees worldwide. We underwrite more than 100 classes of specialty insurance in over 180 countries. In brief, we have the global reach, unique insight and financial stability to help you succeed.

*As at December 31, 2024
**As at June 20, 2025

Edited January 3 by Alan de Enfield

[Russ T]

5 minutes ago, Alan de Enfield said:

 

And for the 1st time my insurers have included a clause :

 

If Your Craft , tender or toys are fitted with Lithium- ion batteries they must be charged within daylight
hours , must not be left unattended whilst being charged and they must be used in accordance with the
manufacturers’ recommendations/instructions.

So no more phone/laptop charging after 4pm in winter.

[Alan de Enfield]

3 minutes ago, Russ T said:

So no more phone/laptop charging after 4pm in winter.

 

And no 'nipping out' for a quick one and leaving your phone/laptop on charge.

[Russ T]

6 minutes ago, Alan de Enfield said:

 

And no 'nipping out' for a quick one and leaving your phone/laptop on charge.

We have an inside toilet.

[MtB]

I've not noticed any equivalent clause in the insurance for my hovel on the bank.

 

It does say no bonfires within 100 metres of my thatched roof though, so maybe that covers it. 

 

I'm more concerned about taking the actions needed to avoid a fire in the first place (or I hope I am anyway) in both the hovel and in the boats, than I am about what the insurance says or doesn't say. The consequences of a fire in a house or a boat extend WAY beyond making an insurance claim so better to work out how to avoid needing to need to claim in the first place. 

 

Yes its perhaps helpful to consider what insurance companies require but that seems, somehow, slightly off the point. 

 

 

 

 

[Arthur Marshall]

 Which all begs the question that most people, including me, have no idea what powers their devices.  Nowhere in the specs of my tablet nor phone does it state the nature of the battery.

[David Mack]

17 minutes ago, Arthur Marshall said:

 Which all begs the question that most people, including me, have no idea what powers their devices.  Nowhere in the specs of my tablet nor phone does it state the nature of the battery.

Exactly. That and GJW's woolly answer on 'lithium extinguishers' make it hard to know what is actually compliant with insurers' requirements. Or perhaps means that the insurers' requirements are unenforceable, and that a claimant who pushes back will get a payout in the end because the requirements are too vague.

[MtB]

34 minutes ago, Arthur Marshall said:

 Which all begs the question that most people, including me, have no idea what powers their devices.  Nowhere in the specs of my tablet nor phone does it state the nature of the battery.

 

I think the lesson is that anything rechargeable is lithium of one flavour or another and not to be trusted whilst being charged.

 

Then drilling down into that, anything with a reputable household brand name on it (that isn't a fake!) has probably been well designed and very unlikely to catch fire.

 

Everything else and especially "compatible" things (e.g. a battery for your drill marked "Makita-compatible") and anything by a weirdly-named manufacturer is going to be cheaply made and capable of catching fire unexpectedly during charging. 

 

SO my suggestion is rather than checking your insurance policy, decide to charge your weirdly-named rechargeable things only while you are present so you'll notice if they catch fire, and secondly do it in a place where a fire can be contained and won't spread easily, e.g. on a kitchen worktop not on the sofa. 

 

 

 

And by the way, you can get yourself a lithium fire extinguisher from the same shop that sells unicorns. 

 

 

 

Edited January 3 by MtB
expand on the point

[Russ T]

13 minutes ago, MtB said:

SO my suggestion is rather than checking your insurance policy, decide to charge your weirdly-named rechargeable things only while you are present so you'll notice if they catch fire, and secondly do it in a place where a fire can be contained and won't spread easily, e.g. on a kitchen worktop not on the sofa. 

But, if you have a GJW policy, it becomes more of a requirement than a suggestion.

 

You could, of course get one of those battery charging safe bags, but it makes it difficult to read the laptop when its inside the bag.

 

[GUMPY]

https://amzn.eu/d/cuZW11Y

 

That sorts the portable stuff

[Alan de Enfield]

1 hour ago, MtB said:

And by the way, you can get yourself a lithium fire extinguisher from the same shop that sells unicorns. 

 

 

They do not appear to have any unicorns available - maybe they are on back-order.

 

 

 

It utilizes a non-toxic extinguishing agent called AVD (Aqueous Vermiculite Dispersion) which is deployed as a mist. The mist creates a film over the surface of the fire, which quickly dries and forms an oxygen barrier, cools the fire, and prevents re-ignition.

One of the key advantages of the Lith-Ex fire extinguisher is its ability to handle lithium-ion battery fires where traditional powder-based extinguishers may not be effective. The extinguisher's design is easily recognizable, ensuring that it stands out when needed during emergencies.

The extinguisher has a 21A fire rating for wood, paper, and cloth fires, indicating its effectiveness against such materials. It is also safe to use on live electrical equipment up to 1000V, making it suitable for a variety of applications, including vehicles, aviation, marine, and medical facilities.

[Gybe Ho]

18 minutes ago, Russ T said:

 

You could, of course get one of those battery charging safe bags, but it makes it difficult to read the laptop when its inside the bag.

 

 

I watched a fire crew training day video that demonstrates smothering a lithium fire can have a negative outcome. The fire crew deployed a car sized tarpaulin to completely cover a car with an active lithium battery fire and then continued to aim a water mist over the whole car. A few minutes later the car exploded knocking over crew.

 

In my view there are only two viable options for extinguishing a lithium fire namely, time or an Olympic sized swimming pool. The best option for a narrowboater tackling a main battery lithium fire would be running away or a large builders shovel and a side hatch alongside the battery compartment.

 

I suppose a charging safe bag would facilitate throwing a fizzing lithium AA battery overboard.

[Gybe Ho]

59 minutes ago, Russ T said:

But, if you have a GJW policy, it becomes more of a requirement than a suggestion.

 

 

I wonder how GJW would respond to a narrowboat owner who claims to have fitted a "canal" as the optimum lithium compatible fire extinguisher.

[TunnelTiger]

8 minutes ago, Alan de Enfield said:

 

They do not appear to have any unicorns available - maybe they are on back-order.

 

 

 

It utilizes a non-toxic extinguishing agent called AVD (Aqueous Vermiculite Dispersion) which is deployed as a mist. The mist creates a film over the surface of the fire, which quickly dries and forms an oxygen barrier, cools the fire, and prevents re-ignition.

One of the key advantages of the Lith-Ex fire extinguisher is its ability to handle lithium-ion battery fires where traditional powder-based extinguishers may not be effective. The extinguisher's design is easily recognizable, ensuring that it stands out when needed during emergencies.

The extinguisher has a 21A fire rating for wood, paper, and cloth fires, indicating its effectiveness against such materials. It is also safe to use on live electrical equipment up to 1000V, making it suitable for a variety of applications, including vehicles, aviation, marine, and medical facilities.

 

OK, we know Li extinguishers are available, but do they work? Conventional extinguishers aren't always effective on 'normal' fires. Would a Li extinguisher give a false sense of security. Best to assume a Li fire can't be extinguished and try not to have one. 

[Jen-in-Wellies]

Back on topic. LEDs need something to limit the current. The voltage can vary widely. Unless the OPs candles are using a resistor to set the current, most LED driver chips can tolerate a widish band of voltages. Enough to make the Alkaline vs NiMH question moot. 

 

[Russ T]

8 minutes ago, Gybe Ho said:

 

I wonder how GJW would respond to a narrowboat owner who claims to have fitted a "canal" as the optimum lithium compatible fire extinguisher.

Given, the response they gave me "would suggest that you contact the battery and/or fire extinguisher manufacturers for guidelines of the compatibility of the fire extinguisher that is specific to your installation".I would guess that if sinking the boat is an accepted method,recommended by the extinguisher supplier, the insurance company might pay out. However, given the extinguisher company is likely to sell no extinguishers dispensing this advice it seems unlikely they would suggest it. However, it may suit the battery supplier.

[Russ T]

21 minutes ago, TunnelTiger said:

 

OK, we know Li extinguishers are available, but do they work? Conventional extinguishers aren't always effective on 'normal' fires. Would a Li extinguisher give a false sense of security. Best to assume a Li fire can't be extinguished and try not to have one. 

I thought the usual advice was that an extinguisher was a tool for getting you past the fire out of the vicinity to safety, not necessarily for putting the fire out. I may have dreamt that though. So given a fire that has already been started by a lithium battery and set fire to the surrounding woodwork, which extinguisher do you select?

Quote

Create a Safe-Escape Plan

Everyone aboard must know and understand how to act in case of an emergency.

Do not attempt to fight lithium-ion battery fires – get out, stay out.

They can spread rapidly, and traditional fire extinguishers may not work.

Keep all escape routes clear at all times, as you may be further hampered by a dense toxic vapour cloud.

Never forget this ...

• Get out and stay out - If a device or battery starts making loud popping, hissing or screaming sounds, or emits toxic vapour/smoke, or catches fire, raise the alarm, warn others, turn the motor off if you can without delaying your escape or creating sparks
• Once out stay out and call 999 (inland/in harbours) or ch16 (on coastal waters) for help immediately
• Keep well clear of the boat.

https://www.boatsafetyscheme.org/stay-safe-advice/lithium-ion-battery-safety/installed-lithium-ion-batteries/

Edited January 3 by Russ T

[alias]

8 minutes ago, Russ T said:

I thought the usual advice was that an extinguisher was a tool for getting you past the fire out of the vicinity to safety, not necessarily for putting the fire out. I may have dreamt that though. So given a fire that has already been started by a lithium battery and set fire to the surrounding woodwork, which extinguisher do you select?

 

It is indeed, which suggests that MtB's advice to manage the risk rather than worry about insurance (and Li extinguishers) may be good advice.

 

After all, in the event of a total loss one could always assure the insurers that there was an extinguisher available, but it was lost in the fire as it was necessary to evacuate rather than fight the fire.

 

Perhaps Bizzard will be here soon to advise on charging on a meccano gantry outside the boat, with the battery suspended by thing string that will burn through quickly in the event of fire and dump it in the canal.

Edited January 3 by alias