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> The fires in HSS in Germany were determined using web crawling for the year 2023 because no other data was available. All other probabilities were calculated using researched data.

HSS may also be underrepresented in the scrapped data due to the method used. The document sections Discussion and Limitations and Outlook touch about this. The authors highlight a lack of common categorization of fires types and count as well as the need for a standardized reporting framework.

Another warning made by the author is that their document investigates the number of fires but not how much damage was done.

It will be interesting to see what it does for fire fighting if we start adopting batteries on large scale in our homes. EVs already pose a significant challenge in European cities. Easy enough for electric cars which can be put into some sort of container to handle the fire, less easy with electric busses. I’m not sure we have a good strategy in place yet here in my city. So far the strategy seems to be “well, it was lucky it caught fire outside the main streets”.

I imagine it’ll be wild if a fire breaks out in a line of town houses with battery storages. If it’s as difficulty to put out as EV’s then you’re probably going to have a hard time containing it to just a few houses.

> If it’s as difficulty to put out as EV’s

EVs do not all share the same battery chemistry. Many have LFP batteries, and these are common for home batteries too. You can go on YouTube and see people drilling into an LFP battery with only a little smoke to show for it.

Right exactly. Any discussion about this topic that doesn’t separate LFP (lithium iron phosphate) based batteries from the wider discussion about lithium ion is missing one of the biggest changes to battery tech in recent years. Not all lithium based batteries share the same fire risks - there are enormous differences now.

Increasingly EVs and especially backup batteries use the LFP tech - you can charge it to 100% without harming the battery unlike previous lithium ion batteries, and they don’t really catch fire.

This paper even acknowledges LFP is significantly safer, mentioning it once, but doesn’t dive into the significant improvements. Again, many EVs (including brands like Tesla etc) already use LFP packs in many cars, and the usage is only increasing. Tesla’s generation 3 powerwalls (home backup battery) are LFP too, its really taken off for home power storage for very obvious reasons - they don’t really catch fire, and you don’t need to worry about charging to 100% harming the battery over time.

> what it does for fire fighting if we start adopting batteries on large scale in our homes

Battery fires do not change much in the first stage. They can be cooled and extinguished (on the outside) with water, but initial reactions are violent for sure, see videos on YouTube.

The long term strategy for firefighters will likely consist of removing the battery (coordinated or forcefully) from the house and then dumping it in a thick layer of sand or water where it can react until it's done.

I wonder if the reduction in entire houses being reduced to a rubble filled crater by gas pipeline explosions will counterbalance these home battery fires as we electrify homes.

Not to mention burned down garages/houses because of ICE vehicles combusting.

Of course people parking their ICE vehicles under, in, or near where people live is completely normal and socially acceptable. Even though they do occasionally burn.

And when I say occasionally, I actually mean: vehicle fires are most common reason for fire trucks to be called. And the overwhelming vast majority of those fires are good old ICE vehicles catching fire. That's not news because the media would be in a permanent stat of OMG, another one burned down hour more or less 24/7 around the year. If you think that is exaggerating things a bit, The US actually has hundred of thousands of vehicle fires reported per year causing billions in damage. And a year is only 8760 hours. You might want to consider your fuel bomb on wheels a bit further from where your loved ones reside, just saying.

Batteries are mostly safe. There was (past tense) a problem with low quality cheap Chinese e-bikes using unsafe and uncertified components. That already is being addressed through stricter regulations and tariffs. For the same reason, the TSA is now completely fine with you bringing phones and other battery equipped electronics on planes.

Home storage systems are far less problematic and usually involves professional electricians and using quality components from very responsible manufacturers with stellar reputations. I'm sure there are some isolated cases of these things having issues. And I'm also sure that that's not going to be a huge number of incidents. And that that pales in comparison to the statistics on gas boilers/furnaces, ICE vehicles, etc.

The (mock) outrage here is very selective and targeted. There's a crowd of fossil fuel funded lobbyists out there promoting any article that serves their agenda. They drip feed news papers, magazines, etc. with a non stop flow of articles to promote their agenda of spreading FUD about EVs / renewables.

I'm sure this is otherwise a fine article. And maybe somebody even is peer reviewing it; the site wasn't very clear on that (other than the 0 citations statistic). But is it really that interesting / world shocking? Why does dry bit of otherwise completely uninteresting statistics literature end up featuring on the front page of HN and getting tens of thousands of views?

A fossil fuel fire can be extinguished by snuffing it. By a fire extinguisher if it's caught small enough, or by a fire department with sufficient quantities of water.

Lithium Ion battery fires are self sustaining. Like with thermite, they produce their own oxidizer - they can't be snuffed. You might be able to flood one and cool it to the point where it self extinguishes (creating a flood of heavy metal contaminated water), use special equipment to drown it, or just let it burn itself out (spewing toxic gasses and at least three times the heat of petroleum fires) but once they are going, they are far more of a disaster than other kinds of common fires.

And even if put out they can re-ignite later forcing salvage yards to keep them physically isolated; causing all kinds of follow on problems that don't exist with traditional vehicles or other battery tech.

As others noted, this study did NOT explore these follow on effects, which is unfortunate. Perhaps they really aren't as bad as they appear - it would be nice to see them studied as well.

I'd prefer to have the battery outside the house, with a concrete wall between it and the house. Or just have it 10 feet away, like where you'd put a generator.

Mine's in my garage, which is breezeblock construction, and the garage doors are insulated, so it keeps it away from temperature extremes - which will cause issues with an outside battery dependending on local climate minimas and maximas.

The SolarEdge battery has a built in fire suppression system that triggers if thermal runaway is detected, which should be enough time to evacuate (in the UK it's also mandatory to have a smoke alarm fitted in your solar "plant room").

Mine is outside for this very reason.

At the time Powerwall2 were the best value/capacity by a country mile, but I didn't trust Musk to not burn my house down.

So its outside, with a very large planting trough above it to provide some level of weather shield, and a strategic supply of sharp sand if the powerwall goes full Musk.

I'm sure that's an option for large, (semi-)detached houses. But it's not an option for the small homes or apartments that the vast majority of people live in.

That's where grid-scale energy storage comes in then. Or at least a less volatile battery chemistry. Not every solution has to be individual unit sized

Most generators are installed within 4ft of the exterior house wall.

A genny has a 12V car/lorry battery to start it. My work one is basically a lorry diesel motor on a floor bolted chassis. It is the other side of an external wall (double skin of brick). Ironically enough the genny is inside the same room as the hot water boiler which is gas powered. The original heating was a coal fired boiler which was converted to a weird oil squirting "hair dryer". That's all gone now.

The fire risks that I worry about do not really include the genny. The fridge in the kitchen is potentially far worse. I have, of course, put in a fire detection and suppression system inside the computer room.

At home I actually have a more involved fire risk assessment than at work. My wife does dog boarding at home and one day I will stop her leaving a cloth to dry on the cooker ... sigh. Anyway, making sure that humans and dogs get warned and get out safely is quite involved.

As we all know there are three ingredients required for fire: a source of ignition, a combustible material and finally: oxygen. Remove one and fire does not happen. Unfortunately some reactions will generate copious amounts of heat and oxygen, ie all three requirements for combustion and become self sustaining. Lithium batteries for example can do this. It's a bit of a nightmare but techniques are being developed to deal with "self igniting metals" and the like.

I drive an EV.

The reason to put the generator away from the house is carbon monoxide poisoning, not the fire risk from a battery.

Having the generator within 4 feet of a door or a window that can open is a bad idea.

You'll also want the exhaust port pointed away from the house.

"You'll also want the exhaust port pointed away from the house."

Chimney in my case.

Diesel fuel is particularly hard to ignite which makes it not too much of a worry in a fire. By the time the fuel tank is on fire the fire department has given up on your building and are just trying to stop the spread to other buildings.

Seeing how hot a battery fire is, I'd want it 10 feet away. Or a concrete wall between. None of that is expensive. And you can sleep safe!

A genny does not have a Li-Ion battery.

A genny:

https://en.wikipedia.org/wiki/Curtiss_JN_Jenny#/media/File:F...

"it" in that sentence refers to battery banks and not generators.

A problem with keeping lithium batteries outside is that it gets way, way too cold in many parts of the world for them to survive charge cycling.

I mean: Sure, there's ways to improve that. There's even climate-controlled outdoor racks, and rack-mount batteries from vendors like EG4 to slot into them.

But a common goal of home battery arrays is to improve the energy efficiency of that home. Heating (or, I suppose in extreme cases, perhaps even cooling) a battery box runs counter to that goal.

Note that the research is centered on Germany, where there is a bit more of a default-deny approach to electrical safety.

Here in the US, some of the pictures I've seen of sample finished installations that the installer is proud of have been downright scary. Like giant wall of 2V batteries with terminals coming out horizontally, open bus bars tying them all in series to make 48V, and then the leads going to the inverter just draped over the entrance to a wiring trough with a rough edge! There was probably a fuse as part of the inverter itself, but no protection for the batteries themselves.

I'm guessing it has to be a case of code inspectors not particularly caring or knowing about the DC side? Although with that kind of current capacity, perhaps the wiring itself is considered a fuse...

>I'm guessing it has to be a case of code inspectors not particularly caring or knowing about the DC side?

I'm inclined to agree with this. US electrical code, especially in recent years, is pretty robust and has gotten to the point where people groan about excessive safety features(tamper resistant outlets required in all new dwelling spaces, arc fault circuit breakers, whole home surge protection all make wiring a house significantly more expensive than 15 years ago). Inspectors are pretty good at catching grounding and other issues. That said we don't yet have generational knowledge of PV and battery systems. A lot of installers are still learning by doing, it feels.

Are you sure it wasn't just DIY un-permitted work, though?

It is always important to remember that the National Electric Code isn't national.

It is up to the states or other (more-local) AHJs to adopt it (or not). And many simply have not done so.

For example: A person building a single-family home in Meigs County, Ohio, has no electrical code to follow, nor any electrical permits to pull, nor any government inspections of any electrical work. (Lacking code, there's no standard by which to permit nor to inspect the work.)

> excessive safety features

Well your average electrical wiring will live on for 50 years or more. The German electricity subreddit routinely has horror shows dating from shortly after WW2, sometimes even from before that, that are still in service. That means whatever you "save" money on now will haunt you and reduce your home's safety needlessly for decades.

As for tamper resistant outlets and surge protection, these things aren't that much more expensive - (Schneider Electric ones are 1€ more expensive in the tamper-resistant variant, but admittedly that's Germany and not the US), and surge protection adds about 700€ in material costs for a three-tier protection. The only thing in your list that is really expensive are the AFDDs, daaaamn they are expensive, but so worth the money.

It's not about the money. It's about the hassle of having stuff that represents a usefulness and longevity downgrade over what it replaced.

What about these is a downgrade?!

Surge protection remains useful until it triggers due to a surge, and a non-protected home in contrast would just have a lot of the devices inside it fried.

AFDDs may not live as long as a "normal" RCD but replacing them isn't that big of a deal compared to the fire risk it prevents - about 1/3 of all residential fires are due to faulty electrical stuff.

The only thing I can see as annoying are protected outlets, but hey... a slight annoyance compared to a child getting an electric shock, a small price to pay.

Brushed motors routinely trip arc fault breakers, it'a a fundamental problem with them that can't be fixed because brushes will always arc a bit. Normal breakers DGAF. Arc fault and GFI breakers have a way higher DOA and crib death rate than conventional breakers.

The other comment addressed the tamper resistant outlets but additionally the outlets themselves don't last as long because they get used more roughly than non-tamper resistant ones.

> Brushed motors routinely trip arc fault breakers, it'a a fundamental problem with them that can't be fixed because brushes will always arc a bit

What kind of device do normal households use that's still using brushed motors directly attached to mains?! It used to be power drills and vacuums, but it's been ages since I last saw one. Maybe power tools for shops and farms, okay, but in that case just leave that one circuit secured with a plain RCD breaker and keep the rest with AFDDs.

> Arc fault and GFI breakers have a way higher DOA and crib death rate than conventional breakers.

RCDs of ye olde days aka 70s, yes, they tend to get more sensitive as they age for some reason, but modern RCDs are rare to see DOA.

Where have your corded vacuums gone? Or have European ones really moved past using universal motors and onto brushless motors with a driver? I know cordless ones have taken off and they're great for small jobs, but I can't imagine relying on one for thorough cleanups.

Corded power tools still exist and it's nice to be able to plug them into any receptacle where you may be working, but I get that it's a tradeoff you just have to do a little more to work around.

I do hate the issue of having more hidden proprietary software blobs though. One of the reasons I've put off upgrading to AFCIs is that it feels like I've got to really research the differences between brands before I commit by buying into a specific style of panel.

Yeah, "tamper resistant" receptacles are utter trash that just ends up damaging plugs, two prong plugs especially. I had to suffer these in an apartment for a while. I will never subject myself to them. If the code body was looking for problems in need of solving, they should have banned all of the janky residential/builder grade $1 receptacles instead.

AFCI (and increasing scope of GFCI) I think has some merit, but there are a lot of annoying aspects to them. As well as some absolute boneheaded implications of the code - like it would be utterly stupid to put a GFCI ahead of a sump pump (at least without some kind of active monitoring that would alert you if it tripped).

> If the code body was looking for problems in need of solving, they should have banned all of the janky residential/builder grade $1 receptacles instead.

Absolutely, those should not exist. I buy commercial spec grade (Hubbell CR20 or equal) whenever I replace a receptacle in my house, they are ~$3 or so.

If you want the ‘best’, Hubbell HBL5362 is the ticket, very well built with a one piece brass grounding strap, I can get them for under $10, but you need to go to a supply house or Grainger to get this one.

> like it would be utterly stupid to put a GFCI ahead of a sump pump (at least without some kind of active monitoring that would alert you if it tripped).

This was actually added to the NEC in 2020, any 120V sump pump that draws 60A or less requires GFCI protection, even if its cord and plug.

You could rig up monitoring with a current switch, normally open relay, and notification device.

Install the current switch around the load side of the GFCI breaker feeding the sump pump that is wired to the control coil of a normally open relay and wire up a horn, strobe, ESP32 or whatever you want to use as a notification device to the relay output.

When the GFCI breaker trips, the current switch will close the relay and power up the notification device.

If you don’t want to rig it up yourself, there are sump pump monitoring kits with text/email notifications, etc.

Or you can avoid it altogether by installing a 240V sump, no GFCI needed.

I'm with you on the Hubbell's. FWIW Grainger has created a consumer-targeted website called Zoro that's actually become one of my go-to's for home improvement stuff. Although often times I have to spec things by looking through manufacturer's catalogs because their parametric search still sucks.

As for the sump pump issue, I avoid it all together by not using GFCI for mere basement outlets. I live in a state where homeowner work is legal, inspectors actively do not want to inspect it, and following the NEC is legally sufficient but not necessary. Some monitoring is on the table eventually, but will include measuring current consumption to see how often the pump is running.

"FWIW Grainger has created a consumer-targeted website called Zoro"

How the heck did I not know this existed? Thanks!

> FWIW Grainger has created a consumer-targeted website called Zoro that's actually become one of my go-to's for home improvement stuff. Although often times I have to spec things by looking through manufacturer's catalogs because their parametric search still sucks.

Ah, so that’s what Zoro is! I work for an electrical contractor so I can get material from supply houses, but if I ever change careers I’ll definitely be using Zoro.

> As for the sump pump issue, I avoid it all together by not using GFCI for mere basement outlets. I live in a state where homeowner work is legal, inspectors actively do not want to inspect it, and following the NEC is legally sufficient but not necessary. Some monitoring is on the table eventually, but will include measuring current consumption to see how often the pump is running.

Yeah, I’d leave any receptacle in a basement non-GFCI protected unless it’s adjacent to a sink or something. Other than that, all your existing devices are grandfathered in.

Leviton makes some decent meters, here’s what I would suggest using: https://leviton.com/products/1k240-1w

Home Depot sells that as a kit with a meter and (2) CTs for $350: https://www.homedepot.com/p/Leviton-Series-1000-Single-Phase...

> I'm guessing it has to be a case of code inspectors not particularly caring or knowing about the DC side?

I don't know what you saw, but it could have been a "homeowner's special", or some kind of proof-of-concept? Professionals are certainly capable of hackjobs, but I have a hard time thinking that a client would be satisfied enough to pay for what you describe. You don't have to be an electrician to know that some stuff just looks dangerous and poorly done!

No. It was a Faceboot page of a decently popular solar installation company showing off their completed works. There could have been some anti-abrasion thing I couldn't see in the picture, but the lack of fusing was still concerning. (And FWIW I did check the battery datasheets to make sure there weren't internal fuses). I suppose those particular installations might have gotten a pass on inspections due to "off grid", but still.

I do think this stuff would be better off at utility scale, but there's another kind of regulatory arbitrage going on there: some people will accept much lower safety standards in their own houses, while other people are keen to clobber anything with any sort of risk attached in the public sphere.

(climate change is of course not seen as a "risk" in the public sense, more of a "business as usual", because it's too diffuse for blame to attach)

My suspicion is that people simply overestimate their ability to asses risk, thus are tolerant of increased risk in their own home as they’re responsible for it, while other people are responsible for risk in the public realm.

> To save others the clicking and scrolling (if you're mainly interested in the conclusion, as I was)

Thanks. Another solution is to read the abstract at the top.

Isn't this entire discussion academic? You could just not mount it on the structure you live in.

Where do you propose people mount their home battery storage?

>even though California's metering system is all kinds of anti-rooftop-solar now

How do?

Eh I'd revise that to say it's anti-rooftop-without-storage. Basically, the CA grid now has a massive glut of solar generation at midday, and so they changed net metering to not pay anywhere near 1:1 on backfed power (it's a really bad ratio, but I don't remember, maybe like 1:5). On the literature around this change, they noted that it's to encourage people to install storage and do time shifting on the power they generate, to help even things out for the grid.

>Basically, the CA grid now has a massive glut of solar generation at midday, and so they changed net metering to not pay anywhere near 1:1 on backfed power (it's a really bad ratio, but I don't remember, maybe like 1:5)

1:5 isn't "anti-solar" though, it accurately reflects the fact that power is worth significantly less at that point in time.

>it's to encourage people to install storage and do time shifting on the power they generate, to help even things out for the grid.

Yep makes sense. Someone has to bear the cost of providing power when it's expensive to do, and it makes sense to more accurately price the solar energy.

I’d agree with you that it was accurate pricing if they sold power for similarly cheap at that time, such that you could just install storage and profit off of time shifting by backfeeding when there’s not a glut. But I’m pretty sure they still charge their absurd rates at noon on a sunny day.