Thanks for that Mike - that was very interesting.

I wonder how the risks compare with conventional lead-acid?

   - Andy.

There are various kinds of Lithium chemistry batteries ... with different risk profiles.

Not all are as vulnerable to impact, puncture, or external temperatures .. but issues can still happen.

With some lithium battery chemistries, electrical- and temperature- related risks of the battery itself being a source of fire or explosion can be addressed by an appropriate, fail-safe, battery management system.

All batteries of any chemistry store energy, and if for any reason that energy is released quickly, say for example the battery is a victim of fire, rather than the cause, the results can be very nasty. It's also highly probable that smoke and fumes from a battery that is a victim of fire, are going to be hazardous, regardless of whether the particular chemistry might evolve explosive or harmful gases or vapours during faults or normal operation.

In my opinion, after watching the video provided, I believe It is imperative that battery systems for residential  EESS (I realise the video covers mainly EV) are contained within non-combustible, specialized enclosures. These enclosures must be strategically positioned in external or detached structures to significantly reduce the risk of fire propagation. Furthermore, it should be essential to equip the vicinity of the battery storage area with smoke detection systems. Additionally, the availability of a suitable class of fire extinguisher or even an automated fire suppression system is available in case of an emergency. Do the regulations mandate the presence of clear and conspicuous signage to denote the existence of Energy Storage Systems (EESS) within residential properties ? If not, why? It would serve as a critical measure for safeguarding the emergency response teams, particularly firefighters. The signage should be akin to that of a firefighter’s switch, providing unequivocal notification that battery storage units are installed on the premises. 

Where do you draw a line with all this? Energy storage isn't exactly unique to formal EESS - I bet there's a Li-Ion battery in your laptop or phone.
https://www.youtube.com/watch?v=jTbUP0sGQT8
I've even had a case of a TV remote control becoming too hot to touch because one of the AA cells dislodged and shorted (one of those modern designs of cells where the case was +ve and the -ve contact was insulated from the case, rather than the other way around - the -ve spring contact shorted between case and -ve contact).

At some point the functionality/convenience is worth the risk.

  - Andy.

AJJewsbury said:

At some point the functionality/convenience is worth the risk.

That is a good point.

One problem when addressing risks is risk perception.

So, for example, GLS lamp holders often provide no protection against contact with live mains with the lamp removed (although some products include a switch to disconnect the contacts this is not mandatory in safety standards). Products with lamp holders may be accessible, even to children (e.g. table lamps).

Yet on the other hand we won't accept socket-outlets without shutters in a domestic (or educational/nursery) setting, and there have, in the past, been drives to put additional "socket-outlet" covers in educational and nursery settings (totally unnecessary and potentially more dangerous for BS 1363 standard UK socket-outlets).

I think at the moment it's quite easy for people to tend towards batteries being in the "high perceived danger" category, and it might well be the issues with Li-Ion batteries hitting the media.

One problem when addressing risks is risk perception.

Indeed. It would be useful to be able to put some numbers to things. Many reported Li-ion fires feel to be attributed to things with allegedly poor battery managements (e-scooters etc) - whereas devices with reputable manufacturer's BMS built-in (e.g. laptops) feel to be less susceptible (if not tampered with for the purpose of making you-tube videos). Impact is presumably manageable by placement or mechanical protection.

How large are the hazards from an otherwise safe battery being caught up in a house fire stared elsewhere? Presumably most of the time the building will have already been evacuated, and while the effects might be spectacular in the short term, how much extra energy is really added? I suspect there's more energy released from the burning of timber staircase (my rule of thumb for firewood is 1kWh/kg) than contained in a typical domestic EESS.

   - Andy.

I think that the perceived danger of lithium chemistry batteries is a combination of high energy density and no simple means of extinguishing a fire once it has started.

ICE vehicles catch fire regularly. If you have a hand held extinguisher you can normally tackle the fire yourself. If it has gone too far the fire brigade can quickly and completely extinguish it. There appear to have been a couple of multi-story car park incidents where a combination of plastic fuel tanks and badly designed drains allowed a significant spread.

Currently there is no means to extinguish an EV battery fire. Removing the oxygen source doesn’t work, it is just cooled until it finally burns out. Maybe something will be developed but until then there is significant problem with EVs in tunnels, on ferries, in underground car parks, etc.

Large scale battery systems in buildings have typically been lead acid with some nickel iron. These are storing a large amount of energy and are capable of starting fires. There is generally very little flammable material in the batteries themselves. The electrolytes do pose a chemical hazard however I think this is generally dealt with by dilution with large amounts of water. These batteries would normally be installed in dedicated battery rooms designed for the purpose.

The spread of domestic scale lithium chemistry batteries brings two problems together, one they are installed wherever there is space and two as with EVs there is currently no means of extinguishing a fire when it starts. As Andy says I am not sure if they would be a significant problem if the fire starts somewhere else. They may be a problem for the fire brigade as they are an energy source that they may not be able to isolate. In some circumstances the fire brigade call on the electricity supplier to make an external cut to the incoming cable. If they know there is a battery they may decide not to enter. If they don’t know there is a battery they will be put at risk.

The smaller lithium chemistry battery systems that are used in Ebikes and scooters, laptops, drones etc. have enough stored energy to start a significant fire involving surrounding flammable materials and again there is no means of extinguishing them. Maybe they can be thrown out of a window?

Is there a solution to extinguishing lithium fires? There are extinguishants for pyrophoric metals like magnesium or potassium but they may not work with the specific chemistries.