Cheap LiFePO4 BMS?

[peterboat]

1 hour ago, IanD said:

Wasn't that a photo of his setup earlier in the thread, with his much-vaunted "laser-cut aluminium busbars" connecting them all together -- and no temperature sensors, since these would have to be embedded in or sandwiched between the cells?

 

None of which makes any difference to the fact that promoting/recommending NMC battery use on boats is irresponsible. Probably the two best sources of information about lithium batteries on boats are Eric Bretscher at nordkyndesign.com and Rod Collins at marinehowto.com , both have many years of real experience with a wide variety of lithium batteries both on boats and in the lab, Rod has acted as the technical adviser to ABYC on this and helped define the insurance industry standards.

 

I would rate their knowledge *far* above somebody who promotes NMC batteries and sells them on eBay, for obvious reasons. Both categorically state that NMC cells (as opposed to LFP) are *strongly* advised against for use on boats, even with professional design and installation, and just plain shouldn't be used by DIY installers. Not ever. Not even if they're cheap and look cool.

 

The fact that James might be a thoroughly good chap who talks the talk (and one of your mates, who sold you some batteries?) is irrelevent.

Ian, Andrew just pulled something of the internet the picture didn't even show a finished bank as each cell has 4 screws in it to connect to the bus bars. Also they haven't been clamped together. My bus bars are plated for a better connection, the cells shown could have come from any supplier as the company making them is big battery manufacturing company. 

[magnetman]

This is correct. The image I showed was of the type of cell not a completed bank with safety precautions taken. 

 

For real batteries I think the Damen ship handling tug "Sparky" with 2800kWh of LTO might be interesting. Diesel backup generators. Sensible people. 

[IanD]

19 hours ago, peterboat said:

Ian, Andrew just pulled something of the internet the picture didn't even show a finished bank as each cell has 4 screws in it to connect to the bus bars. Also they haven't been clamped together. My bus bars are plated for a better connection, the cells shown could have come from any supplier as the company making them is big battery manufacturing company. 

All diversion. The fact is that NMC are strongly recommended against for boats, *especially* for DIY builds, for fire safety and insurance reasons.

 

Do you think that you -- or James -- somehow know better than all the "experts" and insurance companies? 😉

[nicknorman]

2 minutes ago, IanD said:

All diversion. The fact is that NMC are strongly recommended against for boats, *especially* for DIY builds, for fire safety and insurance reasons.

 

Do you think that you -- or James -- somehow know better than all the "experts" and insurance companies? 😉

There is an implication in there that a DIY build is inevitably dangerous whereas a “professional” build is much safer. However most of the fire issues arise from “professional” builds so the latter is clearly no guarantee of safety. A DIY build may or may not be safe. So the discriminator is not “DIY” or “Professional”, it is “well designed and safe” or not. “Professional” is built down to a price point to ensure maximum profit, DIY may be built without that regard and therefore be better.

[MtB]

1 hour ago, nicknorman said:

There is an implication in there that a DIY build is inevitably dangerous whereas a “professional” build is much safer. However most of the fire issues arise from “professional” builds so the latter is clearly no guarantee of safety. A DIY build may or may not be safe. So the discriminator is not “DIY” or “Professional”, it is “well designed and safe” or not. “Professional” is built down to a price point to ensure maximum profit, DIY may be built without that regard and therefore be better.

 

You're using the term 'professional' to indicate 'paid for', it appears to me. 

 

The other meaning might be said to be 'someone suitably qualified' to do such work. Such people carry a responsibility to 'do it right' and can often be sued if they didn't. So it is not unreasonable to expect a professional to be less likely to cause a fire than a layman. 

 

Happy to believe the stats might say otherwise though!

[peterboat]

17 minutes ago, MtB said:

 

You're using the term 'professional' to indicate 'paid for', it appears to me. 

 

The other meaning might be said to be 'someone suitably qualified' to do such work. Such people carry a responsibility to 'do it right' and can often be sued if they didn't. So it is not unreasonable to expect a professional to be less likely to cause a fire than a layman. 

 

Happy to believe the stats might say otherwise though!

The courts are full of cases where professionals got it wrong!

When we had the garage we had 3 vases against us in one year! We won all 3 but the insurance company wanted to just pay in all 3 cases! It was only us being broody minded that took the hard way

[MtB]

1 minute ago, peterboat said:

The courts are full of cases where professionals got it wrong!

 

Which illustrates my point perfectly. Professionals cocking up get sued, amateurs don't. So professionals have a pressure on them to get it right first time, which amateurs don't. 

 

You are reminding me of the seat belt argument. Most people killed in car crashes are wearing a seat belt. So seat belts must be dangerous and should be banned, right?

[Ronaldo47]

That reminds me of a newspaper report of car accident I read some years ago where the driver, who had been wearing a seat belt, died of his injuries. The report went on to say that, if he hadn't been wearing a seat belt, his injuries would have been worse!

[magnetman]

The battery type question must be a tricky one for people on lightweight sailing boats. Obviously you don't want an out of control battery fire in any boat but if it is miles from shore in a GRP vessel it could be life threatening. Yet there are people who use the NMC type because of the energy density. 

 

I suppose everyone has their own level of risk so if you want to incinerate yourself at sea it's no harm but if your canal boat goes up in flames just when there is a school outing and 23 primary school kids get burned to death on the towpath it is a slightly different story. 

 

So yes. NMC is bad for inland boats. Also on canal boats there is not usually a problem with extra weight in fact a lot of people add completely pointless bricks under the floor. Wouldn't it be nice to have batteries there instead. 

[peterboat]

1 hour ago, MtB said:

 

Which illustrates my point perfectly. Professionals cocking up get sued, amateurs don't. So professionals have a pressure on them to get it right first time, which amateurs don't. 

 

You are reminding me of the seat belt argument. Most people killed in car crashes are wearing a seat belt. So seat belts must be dangerous and should be banned, right?

I disagree, a lot of professionals will let the insurance pay up, we didnt because in each case it was faulty parts, one where the radiator had been reconditioned apart from the inter cooler for the automatic transmission which destroyed the gearbox! Premier radiators were insured by Aviva like ourselves so Aviva were happy to let us take the rap! we weren't and took premier to the small claims which we won! The other 2 cases, customers supplied modified parts for us to fit, in both cases the parts were faulty which we proved in court. Amateurs more than likely would be doing it for themselves so who do they sue?

[nicknorman]

5 hours ago, MtB said:

 

You're using the term 'professional' to indicate 'paid for', it appears to me. 

 

The other meaning might be said to be 'someone suitably qualified' to do such work. Such people carry a responsibility to 'do it right' and can often be sued if they didn't. So it is not unreasonable to expect a professional to be less likely to cause a fire than a layman. 

 

Happy to believe the stats might say otherwise though!

Yes. Well maybe getting paid for it as their primary means of employment and maybe having some piece of paper with qualifications written on it. Although I don’t think that last one applies to a “professional burglar”. Or a member of the “oldest profession”.

 

The telly is full of horror stories perpetrated by qualified professionals!
 

As to sue-ability, a lot of this stuff is designed and made in China. Good luck with suing a Chinese company!

Edited January 8, 2023 by nicknorman

[IanD]

On 08/01/2023 at 09:57, nicknorman said:

There is an implication in there that a DIY build is inevitably dangerous whereas a “professional” build is much safer. However most of the fire issues arise from “professional” builds so the latter is clearly no guarantee of safety. A DIY build may or may not be safe. So the discriminator is not “DIY” or “Professional”, it is “well designed and safe” or not. “Professional” is built down to a price point to ensure maximum profit, DIY may be built without that regard and therefore be better.

There is no such implication -- at least, not that *all* DIY builds are less safe then "professional" ones, because this obviously isn't true, some DIYers are more knowledgeable and capable than some professionals -- and may take more care if it's their boat.

 

But there are a *lot* of DIY bodgers out there who will have a go at something without knowing what they're doing, as evidenced by -- well, quite a lot of DIY that I've seen, videos and posts on the web, you name it. Letting DIYers like this loose on even an LFP system is bad enough, but the worst that's likely to happen is a big hole in their pocket from dead batteries or a cooked alternator. Letting them loose on an NMC system could well have far worse results if things go wrong -- and there a numerous cases in boats and elsewhere where this has happened.

 

A "professional" *should* know what they're doing, assuming they're qualified and working in a field they've been trained in -- which is the definition of "professional", isn't it? That's why insurers demand professional installation for gas, mains electric -- and now some NMC systems, because they have no idea whether a DIY installer is a careful expert or a careless bodger... 😉

 

Which of course doesn't mean it's safe to let a traditional boat sparky who knows about 12V lead-acid batteries and systems loose on a high-power lithium setup, *expecially* not an NMC one...

Edited January 9, 2023 by IanD

[rusty69]

So, after a year of service in our less than dry engine room the batteries are looking a bit sorry for themselves. There was some water in the bottom of the battery box caused by condensation, which also forms on the bus bars before dripping onto the top of the cells.

 

My concern is that if enough water is allowed to build up in a cell top then that cell may short circuit.

 

So, my intention is to insulate the box with closed cell foam and put some heat shrink tubing on the copper bus bars as well as some graphite grease on the cell terminals. There will still be some metal (bolts and washers) exposed to the elements which may benefit from a layer of insulation laid on top of the cells.

 

There is, then a risk of overheating, I suppose, so the insulation may have to be removed in the summer months and/or a fan fitted to the box.

 

Any thoughts of improvements (short of moving them into the cabin) welcomed, particularly on what kind of insulation to use. I was thinking maybe bubble wrap or some type of loft insulation/water tank jacket.

[magnetman]

Have you got enough extra power to run some air across them with a little fan? This could possibly help with the condensation. Maybe put an inverted half drainpipe across the top with a computer fan at one end. 

[MtB]

4 minutes ago, rusty69 said:

So, after a year of service in our less than dry engine room the batteries are looking a bit sorry for themselves. There was some water in the bottom of the battery box caused by condensation, which also forms on the bus bars before dripping onto the top of the cells.

 

 

A couple of points, neither addressing the main thrust of your question. But here goes anyway.

 

1) You appear to have both cable connections at one end. I think it might be better for the cells long term if you moved either the +ve or the -ve wire to the opposite end of the bank. 

 

2) condensation is by definition very pure water so does not conduct electricity. 

 

3) I know you don't want to but frankly, LiFePO4 cells have a much nicer life in a warm cabin. Best place for them is under the bed, next to the cauliflower.

 

Ok that was three. 

 

 

 

[rusty69]

7 minutes ago, magnetman said:

Have you got enough extra power to run some air across them with a little fan? This could possibly help with the condensation. Maybe put an inverted half drainpipe across the top with a computer fan at one end. 

Yes, probably. A fan would make a good addition.

[MtB]

Oh and a fourth point. Lithiums have such a low internal resistance I doubt they ever get hot in normal use, not even in summer. So I doubt you need worry about removing any insulation in hot weather you decide to add. In fact if you have them under a cruiser stern deck, insulation will help keep them cool in summer. Marginally. 

[rusty69]

1 minute ago, MtB said:

 

 

A couple of points, neither addressing the main thrust of your question. But here goes anyway.

 

1) You appear to have both cable connections at one end. I think it might be better for the cells long term if you moved either the +ve or the -ve wire to the opposite end of the bank. 

 

2) condensation is by definition very pure water so does not conduct electricity. 

 

3) I know you don't want to but frankly, LiFePO4 cells have a much nicer life in a warm cabin. Best place for them is under the bed, next to the cauliflower.

 

Ok that was three. 

 

 

 

1. Not sure I understand.

 

2. That's good to know.

 

3.Yeah i know. Really don't want to move them though. The next best place is Mrs Rs wardrobe, and I'm not brave enough to suggest that.

[magnetman]

They are probably too big but some military equipment boxes can be used for batteries. 

 

Ammo cans for example but I think your footprint is too large for that. 

 

It would be nice to have them in their own box with some insulation like that wool made from recycled plastic bottles. 

[MtB]

1 minute ago, rusty69 said:

1. Not sure I understand.

 

Hard to explain in words. Needs a diagram and I dunno how to draw one. 

 

But its moot point, about which lots of boaters love to obsess, to the exclusion of far more important factors. Just ignore it really!

 

[rusty69]

Just now, MtB said:

 

Hard to explain in words. Needs a diagram and I dunno how to draw one. 

 

But its moot point, about which lots of boaters love to obsess, to the exclusion of far more important factors. Just ignore it really!

 

Duly ignored.😂

[MtB]

Just now, rusty69 said:

Duly ignored.😂

 

Well done. You'll go far!! 

[MoominPapa]

10 minutes ago, MtB said:

 

3) I know you don't want to but frankly, LiFePO4 cells have a much nicer life in a warm cabin. Best place for them is under the bed, next to the cauliflower.

 

+1. Our Thunderskys are very content under the bed.

 

The space in the engine room where the LAs used to hang out are now extra tool storage.

 

MP.

[rusty69]

3 minutes ago, magnetman said:

They are probably too big but some military equipment boxes can be used for batteries. 

 

Ammo cans for example but I think your footprint is too large for that. 

 

It would be nice to have them in their own box with some insulation like that wool made from recycled plastic bottles. 

They are kinda in their own box already. Its a large welded box with a wooden top. The top has a gap at both sides, maybe 30 mm. The Lithium cells are a fairly tight fit across the width of the box. It is my intention now that I have removed the cells from the box to insulate the insides and the bottom of the box, add some compression rods/plates on the outside, using the box sides as support, and insulate the bus bars.

1 minute ago, MoominPapa said:

 

+1. Our Thunderskys are very content under the bed.

 

The space in the engine room where the LAs used to hang out are now extra tool storage.

 

MP.

What kind on cable length run have you got, and where did you hide the cables? To get mine under the bed would probably require a 15 ft run. The wardrobe, maybe only 7-8 ft.

[peterboat]

My drive ones live in the engine room on their side, insulation all around them,  even in the ver6hot summer last year no issues with them getting hot.

My leisure batteries live under the back step next to central heating pipes all seems to work ok