Lithium batteries

[Memories]

7 hours ago, Tony Brooks said:

 

Looking at the photos it looks to me as if you will need to pack between the steel bar and batteries with wood to meet the maximum degree of battery movement (1cm?) the BSS allows. It will also give you a chance to reverse that earthing bolt (if it is still needed after the work) so the head is next to the battery. You could then cut or drill the wooden packing to clear the bolt head so the battery can never vibrate against it.

It's not as bad as it looks apparently.

 

Going for the lithium, getting the bay sorted at the same time.

 

I thank all contributors to this topic. I've learnt a lot and have had good advice.

Thanks again.

[Memories]

On 01/03/2026 at 17:44, Memories said:

 

I've gone for a 600ah set up with 3 x 400w Flexi panels.

[Memories]

9 hours ago, Memories said:

I've gone for a 600ah set up with 3 x 400w Flexi panels.

And......and......I fixed my leak💪🧑‍🔧

[blackrose]

On 02/03/2026 at 15:37, Memories said:

Going for the lithium, getting the bay sorted at the same time.

 

I thank all contributors to this topic. I've learnt a lot and have had good advice.

Thanks again.

 

These days you'd have to be mad not to go for lithuim when replacing a battery bank as it's not really much more expensive and the benefits are huge.

 

The only thing is working out the alternator charging arrangements. Otherwise I found LiFePo4 batteries were drop in replacements.

 

I took out 3 x 150ah of domestic lead/acid batteries and replaced them with 2 x 280ah of LifePo4 (Fogstar Drift). They fitted in the same plywood battery box along with the sealed lead/acid start battery and the extra sealed lead/acid buffer battery for alternator charging.

 

While 450ah of lead/acid batteries gave me approx 225ah of usable power (50% of capacity), 560ah of lithium gives me approx 420ah of usable power because I can take them down to approx 20% capacity. The other benefits are that unlike lead/acid you don't need to charge them fully and can stop whenever it's convenient, plus because the voltage range is higher all the 12v equipment on board works better. Also with a specified 8,000 cycle lifespan (down to 80% depth of discharge) they might be the last set of domestic batteries I ever need to buy.

Edited March 9 by blackrose

[Jen-in-Wellies]

16 minutes ago, blackrose said:

Also with a specified 8,000 cycle lifespan (down to 80% depth of discharge) they might be the last set of domestic batteries I ever need to buy.

The BMS on my battery reckons it has done the equivalent of 43 deep discharges since being installed last June. So, 7,957 to go, which at the current (sorry!) rate should last over one hundred years! 😀

[Alan de Enfield]

13 hours ago, Memories said:

I've gone for a 600ah set up with 3 x 400w Flexi panels.

 

3 hours ago, Memories said:

And......and......I fixed my leak💪🧑‍🔧

 

 

You had leaky solar panels ?

[nicknorman]

As an aside there’s been a huge fire in central Glasgow shutting down the main station as an adjacent building collapsed due to the fire. The fire started in a Vape shop. At a guess I would say dodgy lithium battery to blame. Not LiFePO4 of course!

So it just goes to show that whilst the BSS and insurance companies might be getting excited about LiFePO4 leisure batteries in boats, the real threat come from small cheapo carry-on Li powered devices.

 

Maybe vape shops will become less viable due to insurance costs, which would be a plus!

Edited March 9 by nicknorman

[IanD]

28 minutes ago, nicknorman said:

As an aside there’s been a huge fire in central Glasgow shutting down the main station as an adjacent building collapsed due to the fire. The fire started in a Vape shop. At a guess I would say dodgy lithium battery to blame. Not LiFePO4 of course!

So it just goes to show that whilst the BSS and insurance companies might be getting excited about LiFePO4 leisure batteries in boats, the real threat come from small cheapo carry-on Li powered devices.

 

Maybe vape shops will become less viable due to insurance costs, which would be a plus!

I don't think they're getting excited about LFP batteries on boats, but about lithium batteries in general, especially triggered by the increasing number of fires -- some unfortunately fatal -- caused by things like escooters and ebikes, and the fact that they don't realise the difference between these and LFP.

 

Or even worse propose that strict fire precaution measures like the ones I described should apply to all lithium batteries, and when the difference -- like that between diesel and petrol, which everyone understands! -- is repeatedly pointed out to them, say "Oh that's all too complicated, we'll bring in one overall high standard first and worry about relaxing rules to take account of different chemistries later on" -- which I suspect means never... 😞 

 

It's pathetic ignorance -- actually it's worse than that, they've been told about this but are ignoring it because it's easier for them. Maybe it's not everyone doing this, but what I just said came straight from the horse's mouth of a UK organisation which may or may not have some responsibilities for boat safety... 😞 

[Tony Brooks]

8 minutes ago, IanD said:

It's pathetic ignorance -- actually it's worse than that, they've been told about this but are ignoring it because it's easier for them. Maybe it's not everyone doing this, but what I just said came straight from the horse's mouth of a UK organisation which may or may not have some responsibilities for boat safety... 😞 

 

If that is so and reading between the lines then that is appalling because the organisation I image you are suggesting are supposed to have a technical committee to advise on such matters. This suggests the committee do not have sufficient technical expertise to advise, so hey need to call in other people with that expertise. It also suggests that other of their requirements are not properly thought through and technically balanced as to the real risk.

 

As far as I can see the difference between technologies are clear - two technologies as safe as lead acids or even more so, and all the rest. I don't see how that is difficult in any way, the only problem may be in identifying the battery types or cells in homemade systems, and they may have other failure types related to charging than just the cell type, so I MIGHT be persuaded home brews should be banned irrespective of cell type, (sorry Nick, yours should be safer than many commercial solutions). 

[David Mack]

2 hours ago, blackrose said:

 

I took out 3 x 150ah of domestic lead/acid batteries and replaced them with 2 x 280ah of LifePo4 (Fogstar Drift). They fitted in the same plywood battery box along with the sealed lead/acid start battery and the extra sealed lead/acid buffer battery for alternator charging.

So you have 2 LA batteries? Is this a twin alternator system? What do you have between the buffer battery and the lithiums?

[IanD]

1 hour ago, Tony Brooks said:

 

If that is so and reading between the lines then that is appalling because the organisation I image you are suggesting are supposed to have a technical committee to advise on such matters. This suggests the committee do not have sufficient technical expertise to advise, so hey need to call in other people with that expertise. It also suggests that other of their requirements are not properly thought through and technically balanced as to the real risk.

 

As far as I can see the difference between technologies are clear - two technologies as safe as lead acids or even more so, and all the rest. I don't see how that is difficult in any way, the only problem may be in identifying the battery types or cells in homemade systems, and they may have other failure types related to charging than just the cell type, so I MIGHT be persuaded home brews should be banned irrespective of cell type, (sorry Nick, yours should be safer than many commercial solutions). 

If it wasn't so I wouldn't have said it... 😞 

 

The DIY issue isn't going to go away any time soon, because thought there are people like Nick who are perfectly capable of building systems at least as safe as any "professional" install -- though the ABC day boat explosion calls even this into question! -- there's nothing to stop somebody designing/building/programming one badly, with similar consequences.

 

However given that LFP are probably safer than LA and there's no requirement for these to be "professionally" installed or checked, it's difficult to see why there would need to be any "special" measures for LFP other than the usual ones needed to make any electrical installation safe (cables, fusing, insulation...) which are dealt with by BSS testing -- though it's possible that DIY "bare-cell" installs have just too much potential for going wrong, so only pre-built LFP battery/BMS systems would be allowed for DIY (which means the vast majority anyway).

 

Lithium batteries with less safe chemistries (self-sustaining fires) usually referred to as "lithium-ion" should be banned from boat installations, no if or buts -- and for portable appliances using them the same rules should apply as in any home, the risk is just the same. If insurers are happy with people charging things at home, I don't see why boats should be any different.

 

Oh dear, I think I've just spotted a problem with the testing idea... 😞 

Edited March 9 by IanD

[ditchcrawler]

1 hour ago, IanD said:

I don't think they're getting excited about LFP batteries on boats, but about lithium batteries in general, especially triggered by the increasing number of fires -- some unfortunately fatal -- caused by things like escooters and ebikes, and the fact that they don't realise the difference between these and LFP.

 

Or even worse propose that strict fire precaution measures like the ones I described should apply to all lithium batteries, and when the difference -- like that between diesel and petrol, which everyone understands! -- 

I think you are basically right, remember it took the BSS 20 years to drop the need for a flame arrestor gauze in a diesel tank vent 

[IanD]

What is frustrating is that the relevant ISO document (26325) does understand the difference; immediately before the section describing the susceptibility of different chemistries to thermal runaway showing that LFP is massively (hundreds of times) less susceptible to this (see attached plot), it says this (my bold):

 

Because of the wide variations in terms of battery chemistries, construction, volatility and responses to a
thermal runaway event, it is not possible to issue a generic prescription for battery compartment design and
ventilation, and for fire containment and fire-fighting mechanisms in the event the latter are considered to be
necessary. It is incumbent on the boatbuilder and battery installer to consult with the battery manufacturer
and supplier to determine an appropriate compartment design and venting mechanism, and appropriate fire
containment and fire-fighting mechanisms, if considered necessary.

 

Edited March 9 by IanD

[blackrose]

8 hours ago, David Mack said:

So you have 2 LA batteries? Is this a twin alternator system? What do you have between the buffer battery and the lithiums?

 

Yes and yes. One alternator is dedicated to the domestic batteries and has a lead acid buffer battery and Victron 50A Orion XS B2B charger between the alternator and lithium domestic batteries. The other alternator charges the lead/acid start battery and the BT batteries via a VSR. That side of the system has been in place since I got the boat over 20 years ago and it works well so I didn't want to mess with it by using the start battery as a buffer for the lithiums. I chose to keep them separate.

Edited March 9 by blackrose

[Memories]

11 hours ago, blackrose said:

 

These days you'd have to be mad not to go for lithuim when replacing a battery bank as it's not really much more expensive and the benefits are huge.

 

The only thing is working out the alternator charging arrangements. Otherwise I found LiFePo4 batteries were drop in replacements.

 

I took out 3 x 150ah of domestic lead/acid batteries and replaced them with 2 x 280ah of LifePo4 (Fogstar Drift). They fitted in the same plywood battery box along with the sealed lead/acid start battery and the extra sealed lead/acid buffer battery for alternator charging.

 

While 450ah of lead/acid batteries gave me approx 225ah of usable power (50% of capacity), 560ah of lithium gives me approx 420ah of usable power because I can take them down to approx 20% capacity. The other benefits are that unlike lead/acid you don't need to charge them fully and can stop whenever it's convenient, plus because the voltage range is higher all the 12v equipment on board works better. Also with a specified 8,000 cycle lifespan (down to 80% depth of discharge) they might be the last set of domestic batteries I ever need to buy.

Just look at what s happening right now with the oil prices, panels are cheap I got 3 x 400w Flexi panels for 600. Just a few years ago that amount of solar would have taken loads of space up, these panels are 1760ish millimetres so not even half my roof space. I have a double alternator set up, leave one of be good acid batteries that are only a year or two old as the starter battery with it's own solar charge set up with about 200w solar.

It's the way to go.

[Memories]

10 hours ago, Alan de Enfield said:

 

 

 

You had leaky solar panels ?

Probably leaking power all over the place

[Jen-in-Wellies]

40 minutes ago, Memories said:

Probably leaking power all over the place

Those pesky electrons get everywhere. Really hard to pick up and pour back in to the wires. 😀

[system 4-50]

1 hour ago, Jen-in-Wellies said:

Those pesky electrons get everywhere. Really hard to pick up and pour back in to the wires. 😀

Take care.  Trying too hard to pick up an unwilling electron can result in you being charged.

[Jen-in-Wellies]

2 minutes ago, system 4-50 said:

Take care.  Trying too hard to pick up an unwilling electron can result in you being charged.

The police will put you in a Faraday cage.

That'll bring you down to earth.

[Jon57]

6 minutes ago, Jen-in-Wellies said:

The police will put you in a Faraday cage.

That'll bring you down to earth.

And charge you with asult and battery. 

[ditchcrawler]

1 hour ago, system 4-50 said:

Take care.  Trying too hard to pick up an unwilling electron can result in you being charged.

You get enough of them and they bite

[Memories]

2 hours ago, Jen-in-Wellies said:

Those pesky electrons get everywhere. Really hard to pick up and pour back in to the wires. 😀

Yeah I'm good but not that good......

[Tonka]

On 28/02/2026 at 21:08, BEngo said:

I have done ours. 460 Ah of lead acid to 460 Ah of Fogstar LFP.  As a DIY job the costs were for the new batteries, new battery box,  the B2B charger, the Mains LFP charger and the cables, cable terminations, clips etc.  I already had the crimping tools etc.  It took me about 2 days work.  Add an extra half day for integrating a suitable existing solar set up, which I do not yet have.

And are your crimping tools the correct ones and calibrated regularly?

[BEngo]

They are the correct ones for the terminations, but not of a standard that has any facility for calibration.  I left all that behind when life in a grey boat and a dark blue suit receded into the distance.

 

Now, If I can't pull the crimped terminations off they will do for a while.🤞

 

[Alan de Enfield]

12 minutes ago, BEngo said:

They are the correct ones for the terminations, but not of a standard that has any facility for calibration.  I left all that behind when life in a grey boat and a dark blue suit receded into the distance.

 

Now, If I can't pull the crimped terminations off they will do for a while.🤞

 

 

 

If it helps here are the 'pull of forces required in the RCD