Jump to content

Cheap LiFePO4 BMS?


jetzi

Featured Posts

13 hours ago, rusty69 said:

 

My very brief reading on the subject suggests that aluminium will begin to oxidise within seconds of cleaning, and so its important to prevent this as soon as possible.

 

My understanding is that Aluminium metal is so highly reactive that the formation of a non-conductive passive aluminium oxide layer when the surface is broken, is virtually instantaneous, hence the procedure of filing bright through vaseline and not wiping away the dirty vaseline when bolting busbars together.

 

When I was working in industry In the 1970's, aluminium castings etc. which were used to construct screened enclosures for electronic circuits, were given a chromate treatment to allow electrical connections to be made to them by soldering.    

  • Happy 1
Link to comment
Share on other sites

Just now, peterboat said:

I bought some Lithium polymer cells from James the interconnects are plated aluminium which clearly solves all these problems, I have 3 x 48 banks, which is a lot of batteries if I had to take  it to bits!

I assume you mean LFP? (LiFePO4)

Link to comment
Share on other sites

15 hours ago, rusty69 said:

Here is a screenshot from today. For your brain cells 

Screenshot_20230105-104008.png

 

Rusty,

I am a bit confused with the display but taking a huge leap .....based on my system, this is what I see.

 

Your bank is at 12.5v but under a load of circa 30A. That says to me your rested voltage is circa 12.8v. That says you are at the bottom end of the voltage range so 20-30% SoC. You are starting then to be in the bottom drop off of cell voltage and your cells will start moving apart. Your max delta is 120mV which I consider fine. Mine is pretty much the same. I operate mine between 12.9V and 13.3v. That doesnt say to me you have a problem with balance. If you charge them up to 13.8v using say 40A, what are the cell deltas then? For me that is the real test.

 

The duck did not fancy going into the oven!

  • Greenie 1
Link to comment
Share on other sites

3 hours ago, IanD said:

I assume you mean LFP? (LiFePO4)

 

James the battery man did also have a very large number of EIG pouch cells (CO20B) and he had the bus bars custom laser cut for them from Aluminium and some copper bus bars too.

 

These are NMC pouch cells in rigid plastic holders and screw terminals rather than bare pouches.

 

I thought @Peterboat had the Valence batteries which are LFP in 4S blocks.

 

James used loads and loads of the EIG cells for his own boat propulsion system.

 

Reading his description I think Peter may have done the same thing. They are thin cells 20Ah each at 3.65v.

 

These ones [img]https://i.ebayimg.com/images/g/zDgAAOSwqR5eQZPo/s-l1600.jpg[/img]

 

 

Edited by magnetman
  • Greenie 1
Link to comment
Share on other sites

4 minutes ago, Dr Bob said:

 

Rusty,

I am a bit confused with the display but taking a huge leap .....based on my system, this is what I see.

 

Your bank is at 12.5v but under a load of circa 30A. That says to me your rested voltage is circa 12.8v. That says you are at the bottom end of the voltage range so 20-30% SoC. You are starting then to be in the bottom drop off of cell voltage and your cells will start moving apart. Your max delta is 120mV which I consider fine. Mine is pretty much the same. I operate mine between 12.9V and 13.3v. That doesnt say to me you have a problem with balance. If you charge them up to 13.8v using say 40A, what are the cell deltas then? For me that is the real test.

 

The duck did not fancy going into the oven!

 

 

The cells in '1' are always out of sync with the other 3, which are much closer. I have assumed that a high delta (27mV) is not acceptable, or the balance could be better.

Here is a screenshot of when I was charging last year, not 13.8, but not far off. Thanks for you input.

 

The initial balancing was done at a max of 10A.

Screenshot_20220803-103025.png

Link to comment
Share on other sites

1 minute ago, rusty69 said:

 

 

The cells in '1' are always out of sync with the other 3, which are much closer. I have assumed that a high delta (27mV) is not acceptable, or the balance could be better.

Here is a screenshot of when I was charging last year, not 13.8, but not far off. Thanks for you input.

 

The initial balancing was done at a max of 10A.

Screenshot_20220803-103025.png


My cells sometimes look not well balanced at mid states of charge, however it is of no concern. The only thing that matters is the balance when the cells go “up the knee” as they approach fully charged. I charge at 14.3v for a full charge, which is nominally 3.575v per cell. If any one cell gets to 3.6v then balancing is triggered, but this rarely happens. But even at say 3.45v/ cell there can be (relatively) big voltage split. As I said, the only important thing is that it all comes together as 3.6 or 3.65v is reached.

  • Greenie 1
Link to comment
Share on other sites

14 minutes ago, magnetman said:

 

James the battery man did also have a very large number of EIG pouch cells (CO20B) and he had the bus bars custom laser cut for them from Aluminium and some copper bus bars too.

 

These are NMC pouch cells in rigid plastic holders and screw terminals rather than bare pouches.

 

I thought @Peterboat had the Valence batteries which are LFP in 4S blocks.

 

James used loads and loads of the EIG cells for his own boat propulsion system.

 

Reading his description I think Peter may have done the same thing. They are thin cells 20Ah each at 3.65v.

 

These ones [img]https://i.ebayimg.com/images/g/zDgAAOSwqR5eQZPo/s-l1600.jpg[/img]

 

 

That was my point, Peter's batteries are LFP.

 

I certainly wouldn't touch a big NMC battery bank on a boat -- especially a DIY one -- even with a very long bargepole while wearing fireproof gauntlets.

 

If James did so then that's his decision and responsibility, but I'd love to know if he told his insurers exactly what he was doing and whether they were OK with that (and when this was) -- which seems unlikely today given the current stated position of marine insurance companies on NMC battery banks...

Edited by IanD
Link to comment
Share on other sites

3 minutes ago, nicknorman said:


My cells sometimes look not well balanced at mid states of charge, however it is of no concern. The only thing that matters is the balance when the cells go “up the knee” as they approach fully charged. I charge at 14.3v for a full charge, which is nominally 3.575v per cell. If any one cell gets to 3.6v then balancing is triggered, but this rarely happens. But even at say 3.45v/ cell there can be (relatively) big voltage split. As I said, the only important thing is that it all comes together as 3.6 or 3.65v is reached.

Ok, thanks. I will look at it again a bit higher up the curve. I think mine are set to balance at 3.4V, and often cell '1' balancing will activate.

 

What do you mean by 'not well balanced' in terms of delta values on your cells, for comparison?

Link to comment
Share on other sites

26 minutes ago, IanD said:

That was my point, Peter's batteries are LFP.

 

I certainly wouldn't touch a big NMC battery bank on a boat -- especially a DIY one -- even with a very long bargepole while wearing fireproof gauntlets.

 

If James did so then that's his decision and responsibility, but I'd love to know if he told his insurers exactly what he was doing and whether they were OK with that (and when this was) -- which seems unlikely today given the current stated position of marine insurance companies on NMC battery banks...

 

OOps !

 

As it happens the EIG cells are actually pretty safe. I've seen tests done on them including physical damage tests and very high discharge and they are OK. I know people don't like NMC but I don't think they are as dangerous as some people think they are. We are all walking around with this chemistry in our pockets these days and very few actual problems.

 

 

As for Peter's batteries he just said Lithium Polymer. This is a cell format rather than an actual chemistry. I think he might have the EIG cells as well.

 

I hope I'm not going to have solicitors after me about this !!! ;)

 

 

As for insurance I don't think the 3rd party insurance companies have anything about battery types on their t&c. Could be wrong and may be worth checking I suppose.

 

Edited by magnetman
Link to comment
Share on other sites

23 minutes ago, magnetman said:

 

As for insurance I don't think the 3rd party insurance companies have anything about battery types on their t&c. Could be wrong and may be worth checking I suppose.

Which is the obvious solution, and the one I will take should my insurance company change their mind. I'm quite happy with third party only insurance, and had it for many years until quite recently in fact.

Link to comment
Share on other sites

10 minutes ago, magnetman said:

I've only ever had third party on boats and cars and no contents insurance. I don't like insurance.

I've always found it much cheaper on cars to go fully comp than third party only, but then I don't think I have been asked to have any of my cars surveyed in a manner other than a yearly MOT.

Link to comment
Share on other sites

1 hour ago, magnetman said:

 

OOps !

 

As it happens the EIG cells are actually pretty safe. I've seen tests done on them including physical damage tests and very high discharge and they are OK. I know people don't like NMC but I don't think they are as dangerous as some people think they are. We are all walking around with this chemistry in our pockets these days and very few actual problems.

 

 

As for Peter's batteries he just said Lithium Polymer. This is a cell format rather than an actual chemistry. I think he might have the EIG cells as well.

 

I hope I'm not going to have solicitors after me about this !!! ;)

 

 

As for insurance I don't think the 3rd party insurance companies have anything about battery types on their t&c. Could be wrong and may be worth checking I suppose.

 

 

NMC batteries regardless of format have had occasional fire problems in *every* application they've been used in -- phones (many cases of this), laptop/powerbank battery packs (banned on planes), planes (Boeing), cars, e-scooters (TFL ban), lumpy water boats (marine insurers ban/restrictions) -- and the culprits in a lot of cases have been pouch-type cells which are most susceptible to damage. It's simply down to the chemistry, NMC is prone to rapid thermal runaway when things go wrong, and any resulting fire is very difficult to put out. The fact that this doesn't happen very often -- there are millions of phones out there -- doesn't change the fact that when they go wrong, they go *very* badly wrong.

 

I'm 100% certain Peter's batteries are LFPs, we've had many discussions about them over the last couple of years 😉

 

Marine insurance companies who cover lumpy water boats certainly do have restrictions on NMC lithium batteries, for example banning DIY installations, hiking premiums, limiting maximum payout. If the same companies cover canal boats then it's very likely they'll have the same restrictions, even though AFAIK there has never been a lithium battery fire on the canals -- probably because there are few boats, and almost all use LFP batteries (for which there is no recorded instance of a boat battery fire).

 

Companies which specialise in canal cover may have no specific restrictions yet, but you can bet that if there ever *is* a lithium battery fire on a canal boat that'll change pretty damn quick, and it may become difficult or impossible to get insurance especially for DIY NMC installations where you want comprehensive or fire/theft cover.

 

Whether this also applies to 3rd party only cover isn't clear, I guess it depends what happens if/when the flame hits the battery pack 😉

 

Also don't forget that the position changes with time as more and more batteries get out there -- 5 years ago there were no e-scooters to speak of, 2 years ago there started to be more and more reports of fires, a year ago TFL banned them. Insurers are becoming more aware of lithium battery risks and are changing their policies, so if (for example) James (or anyone else) asked their insurer 5 years ago whether it was OK to put NMC batteries on their boat and the answer was "yes", it doesn't mean that you'd get the same answer today -- but this probably isn't asked directly every time you renew, it's only actually checked when you take out a policy, and if T&Cs have changed in the meantime (meaning the insurance could be invalid) this will be buried in the small print.

 

The safest position is to tell your insurers in writing exactly what you've installed and get written -- not verbal -- confirmation from them that this is OK, then you're definitely covered. Anything else runs the risk of them reducing or rejecting any claim on the basis that you didn't inform them of the risk, slippery insurance companies play tricks like this all the time.

 

If you want to take that risk, that's your decision... 😉

Edited by IanD
  • Greenie 1
Link to comment
Share on other sites

2 hours ago, rusty69 said:

 

 

The cells in '1' are always out of sync with the other 3, which are much closer. I have assumed that a high delta (27mV) is not acceptable, or the balance could be better.

Here is a screenshot of when I was charging last year, not 13.8, but not far off. Thanks for you input.

 

The initial balancing was done at a max of 10A.

Screenshot_20220803-103025.png

 

I'm with Nick on this one. That doesnt look too bad. Ok cell  1 is a laggard by 70mV at 13.5V (40A charge) which is a bit low but the important bit is when it gets a bit more charge in it. By 13.8V at 40A,  my SoC/voltage curve is starting to get into the knee and then my laggard cell starts increasing faster. I would say that if you are not over 100mV delta at your normal charge cut off point (I always finish my charge at 13.8V) then why worry. It's obviously fine at the bottom end as well. As I said early, its not budged in 4 years since my earlier faffing round trying to balance them. I've given up faffing around.

  • Greenie 2
Link to comment
Share on other sites

2 minutes ago, Dr Bob said:

 

I'm with Nick on this one. That doesnt look too bad. Ok cell  1 is a laggard by 70mV at 13.5V (40A charge) which is a bit low but the important bit is when it gets a bit more charge in it. By 13.8V at 40A,  my SoC/voltage curve is starting to get into the knee and then my laggard cell starts increasing faster. I would say that if you are not over 100mV delta at your normal charge cut off point (I always finish my charge at 13.8V) then why worry. It's obviously fine at the bottom end as well. As I said early, its not budged in 4 years since my earlier faffing round trying to balance them. I've given up faffing around.

Ok. Cheers Dr Bob. I may just clean the terminals up then on block '1' and not bother top balancing them again. They have been working fine in practice, so maybe I was just being overly concerned for nothing. 

 

Regards to the duck. 

  • Greenie 1
Link to comment
Share on other sites

2 hours ago, rusty69 said:

Ok, thanks. I will look at it again a bit higher up the curve. I think mine are set to balance at 3.4V, and often cell '1' balancing will activate.

 

What do you mean by 'not well balanced' in terms of delta values on your cells, for comparison?

 

Well not sure to be honest. Maybe 10 to 15 mV. Not on the boat so I can't check.

Link to comment
Share on other sites

1 hour ago, IanD said:

 

NMC batteries regardless of format have had occasional fire problems in *every* application they've been used in -- phones (many cases of this), laptop/powerbank battery packs (banned on planes), planes (Boeing), cars, e-scooters (TFL ban), lumpy water boats (marine insurers ban/restrictions) -- and the culprits in a lot of cases have been pouch-type cells which are most susceptible to damage. It's simply down to the chemistry, NMC is prone to rapid thermal runaway when things go wrong, and any resulting fire is very difficult to put out. The fact that this doesn't happen very often -- there are millions of phones out there -- doesn't change the fact that when they go wrong, they go *very* badly wrong.

 

I'm 100% certain Peter's batteries are LFPs, we've had many discussions about them over the last couple of years 😉

 

Marine insurance companies who cover lumpy water boats certainly do have restrictions on NMC lithium batteries, for example banning DIY installations, hiking premiums, limiting maximum payout. If the same companies cover canal boats then it's very likely they'll have the same restrictions, even though AFAIK there has never been a lithium battery fire on the canals -- probably because there are few boats, and almost all use LFP batteries (for which there is no recorded instance of a boat battery fire).

 

Companies which specialise in canal cover may have no specific restrictions yet, but you can bet that if there ever *is* a lithium battery fire on a canal boat that'll change pretty damn quick, and it may become difficult or impossible to get insurance especially for DIY NMC installations where you want comprehensive or fire/theft cover.

 

Whether this also applies to 3rd party only cover isn't clear, I guess it depends what happens if/when the flame hits the battery pack 😉

 

Also don't forget that the position changes with time as more and more batteries get out there -- 5 years ago there were no e-scooters to speak of, 2 years ago there started to be more and more reports of fires, a year ago TFL banned them. Insurers are becoming more aware of lithium battery risks and are changing their policies, so if (for example) James (or anyone else) asked their insurer 5 years ago whether it was OK to put NMC batteries on their boat and the answer was "yes", it doesn't mean that you'd get the same answer today -- but this probably isn't asked directly every time you renew, it's only actually checked when you take out a policy, and if T&Cs have changed in the meantime (meaning the insurance could be invalid) this will be buried in the small print.

 

The safest position is to tell your insurers in writing exactly what you've installed and get written -- not verbal -- confirmation from them that this is OK, then you're definitely covered. Anything else runs the risk of them reducing or rejecting any claim on the basis that you didn't inform them of the risk, slippery insurance companies play tricks like this all the time.

 

If you want to take that risk, that's your decision... 😉

Before I converted my boat I asked the insurer if it was ok, he asked what chemistry and brand, he is ok with what I have used.

My little electric truck has Valence batteries but my little electric car has LiPo from James, he tried to get them to burn without success, so I bought some, they have been very good on the Aixam city e huge range in comparison to the Agms it had

Link to comment
Share on other sites

26 minutes ago, peterboat said:

No I mean LiPo I have 3 x 48 volts banks in my little electric car, they have a BMS on each bank I think it gives me 18kwh? I built it a couple of years ago. 

https://en.wikipedia.org/wiki/Lithium_polymer_battery

 

LiPo just means "lithium polymer", it doesn't say anything about the chemistry (e.g. LiCoO2 or LiMn2O4) which is what matters for fire risk -- they could even be LiFePO4. Do you know which they are?

 

(and anyway we're discussing boat batteries not car ones, and I know your boat ones are LFP...)

 

P.S. I've been looking up the "EIG LiPo cells" and they seem to be LiNiCoMnO2 which is commonly abbreviated to NMC, which are in the highest-fire-risk category... 😞

Edited by IanD
Link to comment
Share on other sites

6 minutes ago, rusty69 said:

What you reckon @magnetman are you a higher risk?

 

I probably am now but no intention of driving again so it doesn't matter.

 

 

What actually happened is that I got it wrong. The car was insured fully comp because it is cheaper but in my head it was only 3rd party. This is because I would under no circumstances claim on insurance for something which was my fault. It goes against the grain. Similar with contents insurance. Simple answer is don't own any possessions you can't afford to lose.

 

I really do have a significant dislike of the principle of insurance. Big time.

 

14 minutes ago, IanD said:

https://en.wikipedia.org/wiki/Lithium_polymer_battery

 

LiPo just means "lithium polymer", it doesn't say anything about the chemistry (e.g. LiCoO2 or LiMn2O4) which is what matters for fire risk -- they could even be LiFePO4. Do you know which they are?

 

(and anyway we're discussing boat batteries not car ones...)

 

P.S. I've been looking up the "EIG LiPo cells" and they seem to be LiNiCoMnO2 which is commonly abbreviated to NMC, which are in the highest-fire-risk category... 😞

 

The CO20B cells are alright. High quality, Nobody is going to go up in flames unless they do something very silly.

 

I've experienced a thermal runaway with a jump pack due to overvoltage. Its not ideal but that was cheap rubbish and I did go well above the top voltage. 

  • Greenie 1
Link to comment
Share on other sites

1 minute ago, magnetman said:

 

Simple answer is don't own any possessions you can't afford to lose.

 

 

I was going to suggest an exception could be made for my lithium batteries, but I think the arrangement is that the lithium batteries own me.

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.