Hi Graham,

Without wanting to interrogate the author...

The PAS document requires all indoor locations which contain storage batteries to be ventilated to outdoors (6.5.4) and refers to BS EN IEC 62485 for further information. This does not account for various battery compositions - particularly lithium iron phosphate. There is no direct reference to a baseline ventilation rate (62485 has a calc but it's based on older battery chemestry).

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

Regards,

Peter

And if you're aiming for PassivHaus (or even generally good thermal performance), you need air tightness, so the last thing you want is uncontrolled holes in the walls.

Caravans etc have had this problem for while (most incorporate "leisure batteries") - solutions vary from a compartment only accessible from outside to a interior box with a small plastic tube to outdoors (I've no idea how effective that might be in practice). Usually lead acid, so Hydrogen is reasonably likely.

   - Andy.

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?

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).

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.

The BMMS can do it's thing and cut off the supply. I'm failing to see why the battery being a victim of fire is a pre-requisite for dedicated ventilation to the outside - we normally want to close off such ventilation systems under fire conditions to avoid fuelling said fire.

If vent is required, the required flow rate should be readily available (by calculation or a minimum standard, etc) IMO. 

The BMMS can do it's thing and cut off the supply. I'm failing to see why the battery being a victim of fire is a pre-requisite for dedicated ventilation to the outside - we normally want to close off such ventilation systems under fire conditions to avoid fuelling said fire.

If vent is required, the required flow rate should be readily available (by calculation or a minimum standard, etc) IMO. 

pww235 said:

pre-requisite for dedicated ventilation to the outside

Toxic chemical production. It's not Lithium chemistries either ... many battery chemistries have the problem.

Agreed, this could be cables too ... although in most homes people will be out before cables start burning, the Data guys already have made some decisions on ICT cabling in BS 6701 that haven't happened in BS 7671 (at least as yet).

pww235 said:

we normally want to close off such ventilation systems under fire conditions to avoid fuelling said fire

Hence distance from windows, doors etc. ... the building still needs to comply with other fire regs after changes are made to the electrical installation.

pww235 said:

the required flow rate should be readily available (by calculation or a minimum standard, etc) IM

OK, possibly something to ask the manufacturer.

All good questions ... but the Public Consultation period is the time to make suggestions and provide reasons why provisions in a standard ought to change or be more permissive.

Just to note that, with BS 7671, the relevant Public Consultation period that matters isn't necessarily the one just before the next Edition is published, but the ones on standards that start IEC 60364-xxx and BS HD 60364-xxx, because with the UK being a member of CENELEC, we have to adopt the technical intent of the EU-wide agreed standard. We can make things more onerous, or make minor changes to wording to make things easier to interpret, but if we want to drop or relax a provision, this usually needs to be done before the CENELEC standard is published (that then makes its way into BS 7671 at the next Edition). See pages 15 and 16 of BS 7671:2018+A2:2022 for a list of the standards we (have to) adopt from CELENEC.

pww235 said:

we normally want to close off such ventilation systems under fire conditions to avoid fuelling said fire.

I guess it’s to vent the toxic gases like Hydrogen Flouride that are emitted if cells are punctured or in TR. Though ironically in an “cold roof” attic space a LifePO4 battery would be well ventilated by natural airflow. Also ironically, the battery is less likely to suffer impact damage in this less frequented space.

Also i was under the impression that the recommendation was to stop incoming air and cooking canopy extracts under fire alarm conditions, but to maintain top of stairwell ventilation to aid smoke clearance.