BESS (battery energy storage systems) & Lion battery fire service seminar

[Markinaboat]

Hi,

 

Thought this may of interest to some of you. It's a CPD event for fire service professionals, fire risk assessors etc and was broadcast earlier in the week via the IFE (Institute of Fire Engineers) on the hazards of BESS/Lion batteries. Although this focuses largely on larger installations, the hazards and risks are of course the same. It is quite lengthy at around 1.5 hrs but highly informative.

 

Thanks

 

https://vimeo.com/510434999/6bfd6b7658

[nicknorman]

I only skimmed it but as far as I can tell it doesn’t properly differentiate between the many different types of lithium battery. There are massive differences in combustability and tendency to self-ignite, with the LiFePO4 batteries used by boaters, massively safer than lithium polymer.

 

So whilst the video in context is fine, aimed at boaters it is scaremongering.

[Markinaboat]

30 minutes ago, nicknorman said:

I only skimmed it but as far as I can tell it doesn’t properly differentiate between the many different types of lithium battery. There are massive differences in combustability and tendency to self-ignite, with the LiFePO4 batteries used by boaters, massively safer than lithium polymer.

 

So whilst the video in context is fine, aimed at boaters it is scaremongering.

I was hoping it wouldn't scare monger but thought the evolution of how life will change away form boats would be interesting enough to balance this. Do you think I should remove the post?

[nicknorman]

13 minutes ago, Markinaboat said:

I was hoping it wouldn't scare monger but thought the evolution of how life will change away form boats would be interesting enough to balance this. Do you think I should remove the post?

No need to remove the post provided the context is explained. I didn’t intend to accuse you of intentionally scaremongering, but the juxtaposition of that video (which doesn’t address the many different types of Li batteries and focuses on the most dangerous ones) with boaters who are aware of new fangled lithium batteries making their way onto boats but unaware of the detail, is likely to create a false sense of alarm and worry where none is appropriate.

[Markinaboat]

1 minute ago, nicknorman said:

No need to remove the post provided the context is explained. I didn’t intend to accuse you of intentionally scaremongering, but the juxtaposition of that video (which doesn’t address the many different types of Li batteries and focuses on the most dangerous ones) with boaters who are aware of new fangled lithium batteries making their way onto boats but unaware of the detail, is likely to create a false sense of alarm and worry where none is appropriate.

Absolutely no offence taken. Hopefully our posts here will set the record straight! Thanks for feeding back.

[Awayonmyboat]

I take Nick's points above and he is of course right that there is much variation of risk across LI battery technologies, with the current lithium iron phosphate batteries being much lower risk than previous technologies. However I think much of what is in the video is lithium battery  technology agnostic - it is about the risks if something should go wrong, rather than about the probability of it going wrong. I think there is stuff of relevance in it for all lithium battery users (from laptop users up) but especially for those who build systems based on second hand EV cells. I have seen a lot on the 'net about the benefits of going this way but little on the fire safety issues. If nothing else it is a reminder that all technologies have their downsides and helps to remind us not to overlook these.

 

Interestingly there is some post presentation discussion on the usage of LI batteries on narrow boats - at about 1 hour 10 minutes into the presentation.

 

Thankyou to the OP for posting the link.

[IanD]

1 hour ago, Awayonmyboat said:

I take Nick's points above and he is of course right that there is much variation of risk across LI battery technologies, with the current lithium iron phosphate batteries being much lower risk than previous technologies. However I think much of what is in the video is lithium battery  technology agnostic - it is about the risks if something should go wrong, rather than about the probability of it going wrong. I think there is stuff of relevance in it for all lithium battery users (from laptop users up) but especially for those who build systems based on second hand EV cells. I have seen a lot on the 'net about the benefits of going this way but little on the fire safety issues. If nothing else it is a reminder that all technologies have their downsides and helps to remind us not to overlook these.

 

Interestingly there is some post presentation discussion on the usage of LI batteries on narrow boats - at about 1 hour 10 minutes into the presentation.

 

Thankyou to the OP for posting the link.

Anyone using secondhand EV cells should be aware that these are Li-ion and inherently less safe than LiFePO4, and the risk increases in a home-brewed system where the BMS might be rather less robust and fault-proof than in a car.

 

Not scaremongering, very few BEVs have catastrophic battery fires, but if this does ever happen with Li-ion batteries they're difficult to deal with, and a DIY system really relies on you knowing what you're doing with these cells to be safe.

[nicknorman]

1 hour ago, IanD said:

Anyone using secondhand EV cells should be aware that these are Li-ion and inherently less safe than LiFePO4, and the risk increases in a home-brewed system where the BMS might be rather less robust and fault-proof than in a car.

 

Not scaremongering, very few BEVs have catastrophic battery fires, but if this does ever happen with Li-ion batteries they're difficult to deal with, and a DIY system really relies on you knowing what you're doing with these cells to be safe.

No I think a lot of second hand EV cells are LiFePO4. Not all, of course. The voltage profile of say Li polymer cells don’t fit well with a 12v system, whereas LiFePO4 cells do. I’m not aware of anyone on here who is not using LiFePO4 or something very close.

[IanD]

8 hours ago, nicknorman said:

No I think a lot of second hand EV cells are LiFePO4. Not all, of course. The voltage profile of say Li polymer cells don’t fit well with a 12v system, whereas LiFePO4 cells do. I’m not aware of anyone on here who is not using LiFePO4 or something very close.

Most BEVs use Li-ion cells, the propulsion system is typically 400V using a lot of series modules.

[nicknorman]

11 minutes ago, IanD said:

Most BEVs use Li-ion cells, the propulsion system is typically 400V using a lot of series modules.

Yes, however the used cells coming onto the leisure boating market for domestic use are LiFePO4. Put it like this, everyone on here who has obtained used cells, has got LiFePO4. It might in the future be different for people looking to use them for propulsion, but we aren’t there yet.

[ditchcrawler]

1 hour ago, nicknorman said:

Yes, however the used cells coming onto the leisure boating market for domestic use are LiFePO4. Put it like this, everyone on here who has obtained used cells, has got LiFePO4. It might in the future be different for people looking to use them for propulsion, but we aren’t there yet.

What are they using on the hybrids?

[nicknorman]

23 minutes ago, ditchcrawler said:

What are they using on the hybrids?

Not sure but I think mostly LA traction cells still. Or those lead carbon batteries which are still essentially lead acid.

 

[IanD]

2 hours ago, nicknorman said:

Not sure but I think mostly LA traction cells still. Or those lead carbon batteries which are still essentially lead acid.

 

The high-end series hybrids (the ones done right, not on the cheap) are using LiFePO4 to avoid all the charging/sulphation issues with LA. Cost is still an issue, you end up with a typical boat price north of £200k...

[Dr Bob]

On 13/02/2021 at 23:02, IanD said:

Anyone using secondhand EV cells should be aware that these are Li-ion and inherently less safe than LiFePO4, and the risk increases in a home-brewed system where the BMS might be rather less robust and fault-proof than in a car.

 

Not scaremongering, very few BEVs have catastrophic battery fires, but if this does ever happen with Li-ion batteries they're difficult to deal with, and a DIY system really relies on you knowing what you're doing with these cells to be safe.

Just over a year ago I started a thread on the safety of LiFePo4s wrt to fires. I have a professional interest in this as I am director of a company heavily involved in the testing of Li-ion batteries and have just finished a two year European collaborative programme on assessing the fire hazard of Li-ion. See the following link which provides background.  We are just about to start a further programme developing a novel and very accurate way of predicting run-aways before they occur.

 

We are now 14 months on since that posting and I feel I have learnt more from our work. My assessment of safety of LiFePo4s is that they are very safe if managed properly and I actually think then they are safer than flooded LA's which can short out/explode/give off H2S etc.

One key weakness of Li-ion batteries is dendrite growth - see the thread above. This causes pin point shorts that can lead to run-away ignition. LiFePO4's are likey not immune to this but are obviously much safer. I still havent found any good data on LiFePO4's and dendrites/thermal runaways but that doesnt mean it cant happen.

You avoid dendrites if you do not charge to over 100% or charge at too low a temperature. By keeping the charge under 100% then you remove the most likely cause of thermal problems. Peeps must understand this and this is a key part of the Risk study I have put in place for my battery system. DONT OVERCHARGE.

 

 

[nicknorman]

5 minutes ago, Dr Bob said:

Just over a year ago I started a thread on the safety of LiFePo4s wrt to fires. I have a professional interest in this as I am director of a company heavily involved in the testing of Li-ion batteries and have just finished a two year European collaborative programme on assessing the fire hazard of Li-ion. See the following link which provides background.  We are just about to start a further programme developing a novel and very accurate way of predicting run-aways before they occur.

 

We are now 14 months on since that posting and I feel I have learnt more from our work. My assessment of safety of LiFePo4s is that they are very safe if managed properly and I actually think then they are safer than flooded LA's which can short out/explode/give off H2S etc.

One key weakness of Li-ion batteries is dendrite growth - see the thread above. This causes pin point shorts that can lead to run-away ignition. LiFePO4's are likey not immune to this but are obviously much safer. I still havent found any good data on LiFePO4's and dendrites/thermal runaways but that doesnt mean it cant happen.

You avoid dendrites if you do not charge to over 100% or charge at too low a temperature. By keeping the charge under 100% then you remove the most likely cause of thermal problems. Peeps must understand this and this is a key part of the Risk study I have put in place for my battery system. DONT OVERCHARGE.

I’m sure you are entirely correct, but may I suggest that your last para and the block capitals doesn’t really mean anything unless you define what OVERCHARGING actually means. Ditto charging to over 100% sounds a bit like those folk on Strictly who say “I am going to give it 110%!”. Normally we would consider 100% to be fully charged, so how can you charge to more than fully charged? Slightly rhetorical because I suspect you might mean “don’t continue to charge after reaching fully charged” but that is not exactly what you said.

[Dr Bob]

2 minutes ago, nicknorman said:

Slightly rhetorical because I suspect you might mean “don’t continue to charge after reaching fully charged” but that is not exactly what you said.

Of course you are right Nick and thanks for correcting me.

I used the word overcharging so peeps would understand not to overcharge....and then try and work out what that means. You cannot summarise that in a few sentences! I think we have enough info on these pages to educate people.

[Markinaboat]

All very interesting! I will look at those posts in due course. Thanks

[David Mack]

If there is some chemical state definition of 'flat' (0%) and 'fully charged' (100%), but all the best practice says the battery should always remain between say 20% and 80% charged, then I would expect the battery management system readout to be calibrated so that the 20% state displays 0% and the 80% state displays 100%. That way the ordinary user is in a position to maintain the battery within the common sense (apparent) limits of 0% - 100%.

[Dr Bob]

43 minutes ago, David Mack said:

If there is some chemical state definition of 'flat' (0%) and 'fully charged' (100%), but all the best practice says the battery should always remain between say 20% and 80% charged, then I would expect the battery management system readout to be calibrated so that the 20% state displays 0% and the 80% state displays 100%. That way the ordinary user is in a position to maintain the battery within the common sense (apparent) limits of 0% - 100%.

Yes, and that is the way that a number of us on here run their system. Unfortunately, you do need to take LiFePO4 s up to nearly fully charged now and again .....to top balance them. Some writers on the cruiser forum still believe there is a memory effect which requires charging to near 100%.... and I have seen some evidence of this. I therefore take mine up to 3.5 V per cell about 3 times per year. It's not quite as straightforward as 20-80% but Peter swears it is!

It is interesting you talk about best practice. The best has to be Tesla and now with 6 months experience with my Tesla, I can clearly see their reluctance to go over 80% charge (ever) and reluctance to allow any charging via regenerative breaking when the ambient temp reaches zero. It is pretty easy however to emulate this on a diy boat set up.  

[Rupert S]

I would be very intereted to see how regenerative braking on boats would work!

 

[Rishworth_Bridge]

In reply to Dave Mack's 20-80% point, all the battery charge monitors I have seen tend to 'drift' over time and need re-setting manually. I'm sure there are ways of doing that using cell voltages but it isn't as straightforward as taking LAs up to Float and re-setting the charge monitor to 100%.

[nicknorman]

13 hours ago, Dr Bob said:

 

It is interesting you talk about best practice. The best has to be Tesla and now with 6 months experience with my Tesla, I can clearly see their reluctance to go over 80% charge (ever) and reluctance to allow any charging via regenerative breaking when the ambient temp reaches zero. It is pretty easy however to emulate this on a diy boat set up.  

However we need to bear in mind that as far as I am aware, Tesla does not use LiFePO4 batteries. I think it could be a mistake to transfer “best practice” from one type of Li battery, to a different type (different chemistry).

[Dr Bob]

2 hours ago, Rishworth_Bridge said:

In reply to Dave Mack's 20-80% point, all the battery charge monitors I have seen tend to 'drift' over time and need re-setting manually. I'm sure there are ways of doing that using cell voltages but it isn't as straightforward as taking LAs up to Float and re-setting the charge monitor to 100%.

I just reset mine at 80% or wherever I'm at and press the recent button if I want an accurate count of Ahrs in/out. You dont need to go to 100%.

[Rishworth_Bridge]

Sorry, disagree. If you have LA batteries, as we do, you need to float them regularly to avoid losing capacity. We do it about every 10 days and, if they don't reset automatically, do so manually at the same time. The automatic reset is governed by an inbuilt algorithm which, as I understand it, requires a high enough voltage and low enough charging current before it triggers. When it doesn't reset automatically it will only get to 99 point odd % when the charger is reporting that the batteries are on float. Resetting it to 100% is then automatically correct. We couldn't sensibly reset at anything other than 100% but in a system where that is possible resetting when the monitor shows 80% but the real state of charge is only (say) 79.5% achieves absolutely nothing except progressively to displace readout from reality. If that is what you are suggesting (and I apologise if I have misunderstood you) your 80% readout will be an actual 75% after 10 repeats.

[Dr Bob]

19 minutes ago, Rishworth_Bridge said:

Sorry, disagree. If you have LA batteries, as we do, you need to float them regularly to avoid losing capacity. We do it about every 10 days and, if they don't reset automatically, do so manually at the same time. The automatic reset is governed by an inbuilt algorithm which, as I understand it, requires a high enough voltage and low enough charging current before it triggers. When it doesn't reset automatically it will only get to 99 point odd % when the charger is reporting that the batteries are on float. Resetting it to 100% is then automatically correct. We couldn't sensibly reset at anything other than 100% but in a system where that is possible resetting when the monitor shows 80% but the real state of charge is only (say) 79.5% achieves absolutely nothing except progressively to displace readout from reality. If that is what you are suggesting (and I apologise if I have misunderstood you) your 80% readout will be an actual 75% after 10 repeats.

I never ever look at SoC. It lies.

I reset the meter to reset the Ahr in/out. This can be done at what ever SoC you like. I monitor my SoC by looking a the voltage at lowish current draw (ie typical 5A out on ours with fridge compressor off , tv on etc) and knowing how that refers to Ahrs out - from a previously drawn graph. I use the Ahr in/out as a back up check but this drifts if you dont reset it. The key for me is the voltage. The voltage is very accurate in telling you how charged the battery is. The Ahrs help confirm. For me, its like learning a new language. I dont think in terms of SoC. I think in terms of voltage (where is it between 12.8 and 13.3V on discharge or 13.3 and 13.8V on charge) and in terms of Ahrs in/out.