An alternative may be  to have an explosion release membrane to the outside of the house, rather like the 'tear here' deliberately weakened walls and roof designs one sees on larger substation buildings and ammunition dumps and so forth. ;-)

Joking aside,one has to be clear as to the purpose of the ventilation,  the removal of heat can safely be into the house, but the removal of Hydrogen or worse a hydrogen oxygen mix rapidly becomes a serious matter requiring dilution to outside.

Equally for a well functioning lithium battery there is no gas production that vents most of the time, and if it ever it does, you may well have another problem as well namely a serious fire...

This (US) video compares shooting a rifle slug at a primary cell, a modest Lithium Ion battery (2590 prismatic size) and a zinc air cell. https://www.youtube.com/watch?v=PO8Nu3F8mkA

The 2590s are used a lot in the manpack radios, which is sobering,

Mike

pww235 said:

Presumably we can take a sensible approach here and follow battery manufacturer's guidance/recommendations with regard to the provision and rate of ventilation?

Those recommendations would generally be for "normal use" condition and foreseeable fault, and possibly not consider the battery as a victim of fire itself?

DA said:

The PAS is different in that it insists on LD2.

I'm sure the PAS does NOT "insist" on it ...  LD2 is a "should" in a Note to clauses 6.5.6 and 7.2. In a specification type standard, notes are informative not normative, and should is a recommendation - you can declare conformity to PAS 63100 (Clauses 6.5.6 and 7.2) without an LD2 system ... the "shall" is conformity to BS 5839-6.

DA said:

The PAS contradicts this rationale by directing an LD2 approach rather than a risk assessment approach as per BS5839-6.

Again, the PAS does not "direct LD2". See above

DA said:

Just to add Graham, I dont say any of this with a view to installing the “minimum standards”. 

I can follow your explanation, but I have also heard the views of others that say the system is no longer LD3 when you put on the additional detector.

I openly admit to using 'minimum standard' as a very strong term, after the statements about "evidence-based" and "pricing out of the market" ...

However, as I've said in this post, there is no requirement ("shall") for a full upgrade to LD2 in order to conform to PAS 63100.

Coming back to "evidence-based", this is always a difficult issue in standardization. First, people expect standards makers (and Engineers) to take risks they know about into account. Unfortunately, some hazards suffer from poor "risk perception" (both ways - some things are "over-cooked" because people get a bee in their bonnet about a particular issue, some are "too lax" because a serious route to hazard, or use-case, was missed, that seems all too obvious once something has gone wrong.)

pww235 said:

This does not account for various battery compositions - particularly lithium iron phosphate. 

Are they not covered in BS EN IEC 62485-5 ?

Clause 7.3 of that standard clearly says that harmful gases can be produced and contains requirements to help stop the production of those from the BMS - but that doesn't take into account that the battery might itself be a victim of fire, even though the Scope of the standard says it covers private residences.

Having said that, there's a whole list of stuff in Clause 9.1 of BS EN IEC 62485-5 that needs to be taken into account, and ventilation is needed (if a battery is installed at home) to help address BS EN IEC 62485-5:2021 Clause 9.1 b).

gkenyon said:

I'm sure the PAS does NOT "insist" on it ...  LD2 is a "should" in a Note to clauses 6.5.6 and 7.2. In a specification type standard, notes are informative not normative, and should is a recommendation - you can declare conformity to PAS 63100 (Clauses 6.5.6 and

I did say i may have read it wrong. So thank you for clearing it up. Im aware what “should” means on a normal day! 

gkenyon said:

I can follow your explanation, but I have also heard the views of others that say the system is no longer LD3 when you put on the additional detector.

Its not really my explanation. Its written in BS5839-6.

gkenyon said:

I openly admit to using 'minimum standard' as a very strong term, after the statements about "evidence-based" and "pricing out of the market" ...

I didnt think you had used the term minimum standard… until now. 

You have an engineering perspective and I have a cost benefit perspective. Both are equally recognised ways of development. I used the term ‘minimum standard’ to make you aware that im not approaching this issue from a “cheapest option is best”. Simply, that im aware that, given little evidence of issues with BMS operated LifePo4 batteries, this PAS standard will remove access to ESS for a portion of the market.

I understand its difficult to produce standards, and thank you for taking the time to respond to my questions.

David

No, I think I implied through the posts that some thing are indeed that, even if I didn't use the actual term. Apologies for the confusion.

DA said:

given little evidence of issues with BMS operated LifePo4 batteries, this PAS standard will remove access to ESS for a portion of the market.

The "not in the loft" issue (and ventilation etc.) applies equally to all battery chemistries. It's not just about the battery being a cause of fire, but also the potential for the battery to be a victim of fire.

DA said:

I understand its difficult to produce standards, and thank you for taking the time to respond to my questions.

It's a pleasure.

I don't make these things up all on my own, by the way! Experts come together, we list the issues and discuss them, and reach a consensus.

It is a similar process for the IET Code of Practice for Electrical Energy Storage Systems, the 3rd Edition of which I believe is due to start shipping next week: shop.theiet.org/code-of-practice-for-electrical-energy-storage-systems-3rd-edition

Have people seen the post on linkedin by GivEnergy?  Titled

 Industry update 

Stating things like

Away from the PAS and in terms of safety, you can absolutely install GivEnergy LiFePO4 batteries in lofts where appropriate siting, lifting, access and regulations are considered and historic installations are not affected.

This COULD confuse people like when people were advised to fit a Zappi with only an MCB

I saw that too. Crazy to dismiss safety based guidance because it doesn't suit. 

I noticed they claim to be getting BSI to rework their regs too

to balance things out they should also llink to this presentation. The adverts are a pest, but the talk, and some of the images, should be sobering stuff for the 'have a go'  merchants.

Mike

Not contesting the battery should be in a 30 min enclosure, all for that.