Well, that's our intallation unfit for purpose then...

@guthrie - don't worry. PAS_63100_2024 is not a retrospective standard. Probably the large majority of current BESS installations will not comply, including mine. I don't have a mains wired smoke alarm, though I do have a battery powered alarm fitted. I don't have external ventilation to the cupboard the BESS is installed in either.

As the number of domestic solar PV battery installs increases, the industry is looking to raise standards. There are some installs where the location of BESS has clearly been chosen for the convenience of the installer, and without occupant safety consideration in mind. If this standards prompts installers to think again that's a good thing.

Most solar PV faults happen with the external solar PV array and in particular the MC4 electrical connections. DC power is prone to arcing much more than AC power, and faulty MC4 connections can cause a fire. For that reason I would always advocate on roof solar PV rather than in-roof. Stone, cement and tiled roof materials provide good fire resistance to the house, but only some of the in-roof tray mounted systems do. For in-roof systems, the MC4 connections should be housed in fire-proof enclosures.

Incidences of domestic Li-Ion fires are increasing, but these are overwhelmingly from portable batteries in e-bikes, scooters, hoverboards, Li-ion powered toys, portable power-packs and batteries, etc. Many of these items are internet purchased, made in the far east, and don't confirm to EU CE or UK CE standards.

Solar PV BESS is much better regulated already in terms of the safety of the products on the market, but some of the installation locations are questionable and could be improved upon. Fires caused by faulty BESS from reputable solar PV manufacturers are extremely rare. But as the number of installations rapidly increases, such incidents will also increase. I would be much more concerned about DIY BESS installations from a safety point of view.

Solar PV Installers are put in a dilemma at present: Installer A may stand to lose a sale by saying "I shouldn't install BESS in that location" where installer B says "I'll do it". That's why homeowners should be aware of this standard, as some installers might decide to keep quiet about, at least it in the short-term.

Posted by: @allyfish

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is a must read

:-/ It is a shame that the open standard references other standards which are closed. I don't think I can justify spending > £400 for the bed-time reading.

Posted by: @allyfish

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Indoor location of BESS shall have fresh air ventilation openings to outdoors

I suppose this comes from traction batteries which off-gas hydrogen. It is an interesting requirement, particularly the interaction with building regs. These seem to combine (along with fire alarm installation requirements) to push the battery installation out of the dwelling and into the garage or else outdoors, which is unfortunate for homes without a garage or outdoor space.

I feel @transparent may have something to say about the lumping of LiFePO4 batteries into the lithium-ion chemistry (by omission).

Posted by: @allyfish

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Most solar PV faults happen with the external solar PV array and in particular the MC4 electrical connections.

I an eFixx video about solar string isolation which attributed about 49% of fire incidents to DC isolators. See

page 20. I think older solar isolators had a polarity.

Posted by: @chickenbig

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I suppose this comes from traction batteries which off-gas hydrogen

I think you are right, it borrows requirements of IEC 62485 'secondary batteries' - where for older battery chemistry types, Lead acid and NiCd, there are formulae in the relevant parts of the standard for calculations ventilation rates and minimum opening area for naturally ventilated battery enclosures.

But for generic Li-Ion batteries, which part 5 of IEC 62485 refers, there is no mandatory requirement for ventilation. So why it is included in PAS_63100_2024 isn't clear. I suppose having a means of ventilating smoke, toxic and potentially combustible gasses during or after a battery malfunction might be desirable, but in a domestic situation you would 'get out and stay out'.

Ventilation may prevent the enclosure housing the batteries from getting too warm. BESS systems have quite advanced battery management systems, and thermal sensors - battery charge and/or discharge rates are often regulated above a certain temperature limit. Which is why putting BESS in a loft where the insulation is above the ceiling and the roof structure is non-insulated isn't a good idea. 

Posted by: @allyfish

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PAS_63100_2024 is not a retrospective standard.

In theory that might be the case.

But once the house insurers add it to their list of questions, we are likely to find compliance with PAS-63100-2024 becomes mandatory.

Posted by: @chickenbig

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I feel @transparent may have something to say about the lumping of LiFePO4 batteries into the lithium-ion chemistry (by omission).

I certainly agree that the 6 main chemistries of Lithium batteries need to be addressed separately.

And I don't like the idea of placing LiFePO4 batteries outside, where temperatures can drop below zero (Celsius).
Most BMS units will prevent charging at that temperature.
Some might have an auxiliary-port which can be used to turn on a heater within the cabinet... which means we lower the overall storage efficiency of course.

I really need to scrutinise the text of the Standard itself before passing further comment.

Fortuitously I found a link which allowed me to register for an account with the BSI Group who offered a copy at no cost.

Having done so, I then found that I needed a copy of Adobe Acrobat and their FileOpen plug-in.
... which is no good to me because I don't use computers running any of the OS versions which they support. 😖