Fire risk assessment of battery home storage compared to general house fires | Hacker News Reader

Fire risk assessment of battery home storage compared to general house fires

papers.ssrn.com

185 pointsgnabgib205 comments

This is Germany. Here's a summary of the safety regulations.[1] Safety testing by an "accredited laboratory" is required.[2]

The New York City Fire Department reports that lithium-ion battery fires are a leading cause of fires and fire deaths in NYC.[3] NYFD got the city to require UL or equivalent testing for lithium battery fires.[4] This is working for sales within NYC but Amazon is still selling batteries with fake UL stickers.

NYC's big problem is e-bikes and scooters being charged in apartments and stores. Several hundred of those a year now, and they tend to be severe fires. Entire e-bike stores have blown up. Those things need to be lithium-iron phosphate until solid state batteries become affordable.

(A good political move would be to get the incoming administration to require UL or better certification for anything imported that has a lithium-ion battery or a wall plug.)

[1] https://www.batterietechnikum.kit.edu/downloads/Safety_Guide...

[2] https://www.tuvsud.com/en-us/resource-centre/blogs/mobility-...

[3] https://www.nyc.gov/site/fdny/news/Y40203/fdny-warns-lithium...

[4] https://www.msn.com/en-us/news/us/fdny-is-trying-to-curb-lit...

The incoming administration doesn't seem to really be pro upregulating anything. In fact core members of their team believe the firefighters have had way too much political power already in building requirements, etc.

They don't have to add regulations. They just have to suggest that Amazon actually enforce the regulations on the books, instead of allowing fake UL/ETL listings to be accepted as seems Amazon's common practice.

Just tell them that enforcing these regulations will hurt Bezos who owns the Washington Post.

There shouldn't have to be any political reasons at all to enforce safety testing listings, and I would actively discourage anyone from taking that path regardless of their views on any given administration.

Far too many Chinese vendors just treat the "UL circle" as a required marking to forge, along with everything else they're forging on the items. http://www.righto.com/2016/03/counterfeit-macbook-charger-te... is a good teardown that highlights the problems with the fakes.

Amazon has had more than enough chances to solve this problem somehow or another, and it's clear they do not care about it at this point. They cannot claim ignorance after a decade of people highlighting the problems to them. As much as I don't like Walmart, I'd go to Walmart over Amazon for anything electronic (realistically, I'll buy NewEgg or B&H Photo for most things), because I have somewhat more faith in Walmart's supply chains to actually get me the thing I'm buying, vs "binned product fraud" that seems to be Amazon's bread and butter these days.

"Fraudulent markings on poorly designed, unsafe electronics that lack all the safety systems that the markings indicate exist" isn't a political problem. It's a basic consumer safety problem.

Walmart has the same exact marketplace sellers and the same exact problems as Amazon (unless perhaps you go to their brick and mortar stores). The only solution is to shop for only brands that are known to be good and have a reputation to protect, which of course doesn't scale very well beyond our personal preferences.

While they make it a pain and constantly reset it, it is still possible to set the filter for Walmart only on their website. I'm not sure shopping for known good brands works since counterfeits are so prevalent and many third party sellers on walmart seem to just be running an Amazon reshipping service.

I'll go to one of their physical locations if I want something that plugs into the wall. It's likely to be actually what it says on the box, if I do that.

If you tell them that they'll go and ask him for a bribe to avoid tariffs and regulation enforcement.

Better to stick to basic racism and conspiracy thinking and say the China batteries are leaked from a lab to intentionally burn down American patriots homes.

It’s time to enforce these on state and state compact levels tbh.

Tariffs are regulations.

Depending on which requirement they mean, that case is actually interesting. There's a good video from Not Just Bikes about it https://youtu.be/j2dHFC31VtQ ("How American Fire Departments are Getting People Killed")

This is a great video.

The main point is that fire departments oppose bike lanes and safer street designs because of their unnecessarily giant fire trucks.

It's important to differentiate a "Battery Home Storage" system like a powerwall, an EV, or even a bunch of stackable ecoflow's sold at Costco from small-enough-to-be-hackable e-bikes and scooters. Asphalt and gasoline are both "petroleum products", but completely different worlds.

The NYC problems are caused largely by stores and race-to-the-bottom retailers doing DIY spot-welding, homebrew extending of battery packs with the cheapest cells found off aliexpress (and skipping the engineerey-bits like cell testing and cell balancing), and going for the cheapest chargers that skip things like a BMS or any regulator circuitry because it shaves a few bucks in power ICs.

You'll see these things in the $100-1000 battery market.

Your powerwalls and EV's are expensive enough that they probably didn't have to cut those corners. Plus the installation should be permitted and installed.

I'd love to have Amazon require UL certification for anything with burn-the-house-down risk, but this defeats the whole purpose of the cheap-off-the-boat business model of Amazon so that won't happen. "We're just a marketplace, sellers should be able to sell whatever they want." Besides the outright fraud on there, there's also subtle fakery like "UL Certified" electronics where if you take the time to lookup the certification number, you see all that's actually certified is the steel box meets UL "steel box" box standards, nothing about what's actually inside.

UL is also not the be all and end all. You can build a UL certified pack with pretty shit cells. The most important aspect of a good battery is just use good quality cells that don't blow up.

LG produced a bad batch a few years ago and caused a bunch of fires, while other batteries in the same circumstance were perfectly fine.

Cell quality is one thing, but it is also possible and necessary to ensure that cell failures do not cause a thermal cascade that causes adjacent cells to fail. The whole "pack caught fire because of one cell" thing is optional. Ideally a catastrophic cell failure results in some venting of gas and a bunch of blown fuses at the cell interconnect level.

The level of increased risk depends on how many cells are in the battery. A large battery will need to be well-protected against cascading thermal runaway, but a battery with 2 or 3 cells there isn't much difference.

The need for reigning in of cheap dangerous batteries really can’t be understated. There’s so much readily available houseburner junk out there.

I wonder what is going to happen to all the LiIon batteries in cheap gadgets that are being stored in garages and basements. What happens to them in 20-50 years?

They self discharge and become inert, unless Someone plugs them in. They won’t likely just catch fire, but there will be (is) a lot of dangerous to use junk out there.

I just decommissioned about a dozen Li-po batteries from old drone projects. This involves making them truly inert. There was a LOT (>50%) of energy in those batteries after 4 years.

There's an art collective around here that had a massive fire that started from a cell phone that had been held in a lost and found bucket for some years. Apparently it just caught fire one day.

Shit. I have old phones in boxes in boxes that I've forgotten about.

How worried should I be?

It's not likely to catch fire, but... try to get rid of them.

There are likely billions of abandoned devices with lithium batteries sitting the in the back of drawers all over the country, and fires from them randomly bursting into flames seems pretty rare.

But even if 1000 of these things burst into flames a day, that is still 0.04% chance of any given device burning up in a year.

If you are concerned about them, discharge the batteries completely. If you leave the battery discharged, it (very likely) won't start a fire. But it will also continue to self-discharge, which will ruin the battery over time. In which case, the device is likely junk anyway, so you might as well just take them in to be recycled now rather than later.

Just please do NOT throw them in the garbage.

The biggest danger is trying to recharge them after they have been stored for a long time. The anode and cathode might short-circuit and then a fire will likely start. If you want to check out an old gadget or battery make sure to watch it while charging and have a fire safe container or a plan to extinguish the fire at hand.

I've become pretty conservative with old phones, laptops, and the like. If I'm not going to use them/have them repaired I put them somewhere safe and recycle them.

Damn. Art is getting hardcore.

There is a difference between something that stores 5,000 joules (small battery) and 50,000,000 joules (tesla power wall).

Or overstated.

I'm surprised courts have not already held Amazon accountable. They typically won't accept arguments that someone is just a seller, particularly when someone has "deep pockets"

Is amazon the seller or the platform? I think it depends on the product.

The courts don't have to care. There is a good arguement that amazon (unlike ebay) is trying to hide the seller and so should be seller.

Mostly amazon has deep pockets and can be brought to court.

I'd like to see wider adoption of battery swaps. This would mostly solve the problems you describe.

https://www.gogoro.com/gogoro-network/

The only way I could see this being regulated by the incoming admin is if tariffs make the batteries too expensive which would only decrease the scope. The cult claims to want to eliminate all government regulation.

I feel like tariffs may make the problem worse as the cheaper the battery, the smaller the tariff hit, and so people may be incentivised to go even further down the quality ladder

Thinking about it, this sounds spot on.

Indeed there's been a LOT of e-bike battery fires, so that's why with designers and engineers in France we've spent some time designing a battery casing that efficiently contains explosions and flames, to safeguard your home, you can check it here if interested! (it's also a repairable battery, so it saves CO2 compared to a standard battery over the long term. Oh, and we're in the process of doing the UL certification right now)

https://get.gouach.com

This looks great! User-swappable cells, fire-proof casing, convenient handle. Price is still competitive.

I'm currently charging my eBike battery at home in the oven, to contain thermal runaway should it ever happen. This thing would solve this.

Thanks so much!! Appreciated

I've got a tern e-bike with a Bosch motor, I love taking it on long rides. You've made a compelling case for replacing the existing battery, but what does the story look like for replacing cells in 5 years? Do I have to replace them all at once? One at a time as they fail?

Also, how swappable or parallel are the batteries? I'd love to be able to have two batteries for days when I want to ride 100 miles. My existing Bosch battery only has a ~60 mile range and I'd love to push that up.

Also, do they have a usb port on the battery for power? Running lights, charging my phone, or powering a GoPro from the bike battery would be so helpful.

Yes! It will work, and you can also combine it to have a dual battery setup

you can look at the Datex Battery Mixer that we sell as an option when checking out

To save others the clicking and scrolling (if you're mainly interested in the conclusion, as I was), the summary at the end says that the risk of fire starting in your battery energy storage (or in your EV) is lower than that of your average house fire (or in your ICE car). They liken the risk of a fire starting in the battery storage to that of fire starting in a clothes dryer. But, depending on the placement of your batteries in/around your home, the severity of a fire, if one should happen, could end up being worse than a fire that starts in some other household appliance.

I was pleased to read that the risk of fire is reasonable and low; I wasn't sure what to expect, but was afraid the conclusion would be that they're higher-risk. I suppose I expected to see the result that a fire that included large batteries could be a much worse fire. Li ion battery fires can be pretty bad, and those batteries are much larger than what you'd find in your phone or other small electronics.

I still would like to add rooftop solar to my house (even though California's metering system is all kinds of anti-rooftop-solar now). When I last looked into it a couple years ago, battery storage seemed like it was a little too pricey to be worth it, but it seems like that's been changing.

> 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.

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 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'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...

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.

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.

> 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'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.

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

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.

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

A genny:

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

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.

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").

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

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.

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.

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.

> 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.

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.

I can't relate to per-year risk percentage numbers. But the inverse is quite illustrative I find. Here is the expected time between events for each category according to the paper:

General house fire: 360 years

ICE fire: 1100 years

EV fire: 4200 years

Battery storage fire: 20'000 years

Tumble dryer fire: 27'000 years

PV system fire: 71'000 years

This way I can understand that while I might see my house burn, the battery storage is very unlikely to pop in my lifetime. Because these numbers are not very accurate anyway, I've rounded to two digits. The authors note that the number for battery storage in particular are very unreliable.

On the other hand: just looking at probabilities of events does not tell you how lethal or destructive the event will be. And lithium fires are very bad in both categories. Comparing to tumble dryers is not very useful when you factor in the properties of the fire. Quite possibly the danger to life is higher with an EV compared to an ICE, even if the ICE is assumed to catch fire at four times the rate of the EV. In addition, the wear-out failure rate of EV is to be discovered yet, because the fleet is so young. The EV rate may still climb. Or maybe battery manufacturers improve and the danger will be reduced? Some things do get better after all!

The years perspective is useful. But I'm not sure it's useful to compare the danger from different sources of house fires. The bad ones happen at night, and then have more than enough time to cause catastrophic damage whether it starts from a dryer or a candle or whatever. (There are some instructive videos on YouTube of how quickly fires spread in rooms)

After a few years of arguing with people about nuclear safety I'm not sure that this sort of perspective is useful. People make a gut-feel check on whether they feel safe and then just rationalise it. The actual level of risk doesn't seem to factor in to the conversation.

If we're going by the numbers this should probably disqualify the use of home battery storage on safety grounds. We're talking something like 1 home/year catching fire in a large town, those are some crazy levels of damage. If it was 1 home/year being hit by no-harm-detected-but-higher-than-expected radiation people would be seizing the numbers as evidence that a reactor needs to be shut down.

The thing with nuclear reactors is that they don't go off that easily or that often, but when they go off, the impact is both very large (Chernobyl spread to Bavaria!) and very long-lasting in its impact (Chernobyl is still a no-go zone, and to this day you have to inspect and throw away game and shrooms collected in Bavaria if it is impacted by radiation).

Coal power plants have a much larger impact, new ones have been cleaned up, but in the 1960s they were putting lots of radioactive waste into the air which rained down around the world and is still there.

Nothing comes for free. If you have 100 bad things each with an odds of happening once every 100 years, its not going to be a pretty century.

The PV stats seem low to me since Amazon for example started removing solar panels from their warehouse roofs due tu multiple fires in multiple different places.

"The rate of dangerous incidents is unacceptable, and above industry averages"

Amazon took their rooftop solar offline temporarily to inspect and safety work after a string of fires in in 2020. They replaced some of the more shoddy installations, but Amazon warehouse rooftop solar is back online for years since.

Good to know, thanks!

I wonder what the root causes of these bad installations were.

There was a lawsuit a few years ago by Walmart about panels installed by SolarCity in the early 10s. During this time the company was facing financial issues (their model was leasing panels), so did a lot of cost cutting.

The main causes of PV fires are arcing due to poor installation, e.g. loose connections or damaged components. PV is not like household mains power where you have high current for a few minutes (e.g. turning on a kettle), it's like that for hours at a time. You need to be much more careful.

On a residential PV install, each 'string' from the panels to inverter could easily be 10 or more amps at peak output.

Okay, but if your house is on fire the chance of your battery storage catching on fire goes way up.

Sure when the fire expands into other rooms the battery storage may go off too. By that time I hope I'm upwind of the whole debacle. Many "general" fires do not go beyond one room though.

I find this data quite amusing. In another life I cleaned up after things like fire damages. The vast majority of them were kitchen fires and the only one I can specifically recall that was not cooking-related was some dude's hot rod that blew up and set the garage on fire.

> The vast majority of them were kitchen fires

Without any personal or professional reason, I've seen many of them as a casual onlooker. I remain terrified of open pot deep frying over a stove.

But the insurance assessors I've talked to recently do mention a new trend in battery fires - though usually caused by a combination of bad quality, excessive quantity stored and sloppy practices bordering on the abusive.

So in a housing development with 36 homes, we expect one to burn in 10 years? Am I reading that right?

If so, that doesn't sound right to me.

No, all 36 burn in year 360.

That sounds pretty close to right. House fires don't necessarily burn down the whole house with flames to the sky. My home had 2 pretty serious fires growing up (over 20 years): 1/ car fire from grease/oil/gas leaking from our diesel car engine after driving in very heavy rain, 2/ unattended hair dryer overheated (don't know if it was on or off but it was plugged in).

> So in a housing development with 36 homes, we expect one to burn in 10 years? Am I reading that right?

Yep. And - anecdata - it is about correct... if you count all the unintended fires that didn't escalate to a full blown dwelling fire. The classic example is oil overheating and flash-combusting in a pan or pot, and people making that exponentially worse by trying to extinguish it with water instead of just putting a damn lid on it.

Another infamous example used to be (old) people smoking in their wing chair while watching TV and falling asleep with the lit cigarette then setting the furniture or carpets alight. That one has been very effectively remediated by strict fire resistance requirements on furniture as well as requiring cigarette manufacturers switch to self-extinguishing paper.

Seeing a fire truck responding to my direct neighbourhood every 10 years sounds about right.

I didn't read the entire paper, but what I was really curious to hear about was battery chemistry, and I didn't see much in there (unless I just missed it.) I've been bullish on LiFePO4 because of the ostensible safety benefits, but it would be interesting if anyone has taken a look at the safety risks of different battery chemistries head-to-head.

I don't necessarily think that lithium ion batteries are inherently unsafe, but even if their safety properties are in fact acceptable on a societal level, it's hard to grapple with how horrifically violent battery fires can be. There was a video going around of a battery fire where someone got trapped in an elevator with, apparently, an e-bike battery that went into thermal runaway. It's hard to overstate how utterly mangled their body was. Even as someone who grew up with access to LiveLeak and other things I shouldn't have seen, that video and the decimated (shockingly alive, but not for much longer) corpse pulled out of the elevator will be sticking with me for a long time (and reminding me to not bring potentially sketchy high-capacity batteries onto elevators, for whatever it's worth...)

Yeah lifepo4 will not combust badly. Look up will prose on YouTube he does a lot of tests

Indeed, they also can produce toxic smoke... should be in an outdoor pit. =3

How large was the elevator ? Scary but I wonder if you had time to react if you could shove the bike to the opposite side and maybe be relatively fine

I saw the video. It was a very small car, the kind you would see in a small apartment building - something like 4 feet square or 1.25m square, if even. Basically a closet. Edit: to add it wasn't the whole bike but the battery pack itself. It was in his hand.

Pretty small, but I'm not sure if it matters. If any battery starts out-gassing when you're in an elevator, you're probably as good as dead, because the hydrogen fluoride release will quickly cause tremendous damage to you or just flat out kill you; I doubt there's much you can do about it.

So I definitely think that the moral of the story is simply never, ever take a large battery onto an elevator

Maybe solid state batteries can some day give us more peace of mind.

The video shows the entire elevator being engulfed in fire, fumes and light. It was a small lift, but I'd doubt any part of any normal lift would have a safe spot.

Here's a NSFL link of what appears to be the video for those wanting to see just how engulfing it was https://streamable.com/y47pm1

For those wanting to stick to descriptions: the entire elevator (albeit a smaller one) is goes from normal to completely filled with burning toxic gasses in 2 seconds. If it were a large elevator and a phone battery you could probably escape most of the damage by being at the opposite end and exiting quickly after. With a batter that large though it's a bit of a different story.

Being trapped in an enclosed space with something like that, which supplies its own oxidizer and burns very hot, would be a nightmare. It's like wondering if your food can retreat to the safe corner of your oven or BBQ, away from the burner.

As stupid kids, my friends and I found an unused emergency road flare and played with it, outside on a sand pile, where we thought it safe. I still managed to get give myself some lung injury from inhaling a shallow breath from the invisible convection gases rising off it about 3 feet above.

We put a 15 kWh battery storage system in our garage and had to build a fire-rated room around it with a 60-minute fire-rated door to maintain code -- which is a pretty heavy weight steel door. It wasn't easy. All to maintain county code. The funny part is by the time we got the inspection, the fire department had a new inspector and he said "wow, you did all of this for the battery?"

How much did that cost, as a percent of the total cost of the system you built? My feeling is that a requirement like that could make the project financially infeasible for a lot of people.

Consider the U.S. insurance industry and their desire/need to refuse payouts when possible. If a fire occurs and the location contravenes just about any code their staff can find, they will likely refuse payout and it will be time for you to lawyer up. So, in that case, the expense of that special room might be seen as a bargain in the long run.

Sure, I don't disagree with that, but someone looking to do an installation might just decide not to do it at all, seeing the cost of the protection setup. That may or may not be rational, but I could easily see that happening. Sticker shock is a thing, and solar+battery installs are already plenty pricey, even with the cost renaissance we've been seing.

GP/sibling says it added on another 5-10% for them, though, so that's not too bad, though I guess it was a DIY job, and would have cost more to pay someone else to do it.

5-10% of the battery itself. required 1/2" sheet rock, that 60-min door, etc etc. would have been more if I hired someone to do it.

sorry 3/4" sheet rock in case anyone is counting here.... :)

A lot of people probably don't follow the law.

correct. but a lot of people do. and it can be expensive.

Wow. And you can park a car that has a battery with 5x the potential energy in my garage without any additional requirements? Somewhere or another the code doesn’t add up.

Typically the code requires 60-min firewalling of the garage.

For an EV?

I think the op is pointing out that some building codes put huge restrictions on building isolation with stationary storage like powerwalls, but as soon as those batteries are on wheels then regulating cars is someone else's department.

>For an EV?

For a 20 gallon tank of gasoline on wheels.

Also a good point. If each gallon of gasoline is equivalent to about 33kWh of energy, I could have 1.3MWh stored in two ICE powered cars. I guess it’s harder to put out a battery fire than a gas fire?

The way you put out a battery fire is you don't. Last I checked, the current best practice for an electric car that catches fire is to just let it burn to the ground while trying to stop anything around from catching fire.

Not an option in the basement of a building, the temperature will risk structural integrity.

Not to be callous but the "just let it burn to the ground while trying to stop anything around from catching fire." might be the structure over the basement in this case and the keeping other things from burning would be the surrounding buildings.

If firefighters can't access the basement safely, that's exactly what they'll do. They'll protect the exposures instead, ie the neighbouring buildings.

A car itself contains a lot of stuff to burn (tires for example, etc) - look at any burnt out car - it is just a metal shell (until it was an aluminum one). So, i hardly see much difference between ICE and EV here.

The difference is you can extinguish a fuel fire by smothering it. Deny it oxygen and it can't combust. When you do that with a battery fire, it just flares back up as soon you stop smothering it

In theory you're right. On practice - until you're an equipped firefighter, you wouldn't be able to do anything once a regular car develops significant fire.

You can absolutely extinguish a fuel fire early on if the tank has not ruptured. Sand, baking soda, water, dirt, blankets, all work. If the battery on an EV develops an entire short you are not extinguishing it. If it were available, the safest mechanism would be to push it into a hole and bury it

> ... until you're an equipped firefighter...

If my car catches fire (EV, ICE, whatever), I'm going to call a firefighter immediately, regardless of the severity.

Eh, a 5lb extinguisher in good hands has enough punch to extinguish a flaming stock tank of diesel twice so it should put out a car that isn't totally engulfed.

Source: Got to watch a demonstration put on by the local firefighter training center.

Source 2: Anecdotal experience buying burnt out vehicles at auction, the state trucks with extinguishers are typically only a little burnt.

The difference is after a ICE car burns there is a tank full of gasoline still there. With a EV the battery will also burn.

> I guess it’s harder to put out a battery fire than a gas fire?

Yep. With a gasoline car, dump water and foam onto the wreck and that's it. If you're really fancy install a sprinkler system in your garage - you can just DIY it if you want, hook up a water pipe to your water mains with a backflow prevention valve to prevent stagnant water from flowing back, add a few heads like [1], and there you go - assuming your water mains has decent pressure, that should be enough to keep a gasoline car fire in check for long enough so that the firefighters can show up and deal with it properly.

A battery car fire however? That one is much, much harder to extinguish and it burns way hotter. You need much more volume of water to cool it down enough to approach the vehicle safely, it will cause a lot more damage to surrounding structures, and fire departments haven't gotten nearly as much experience as they have with gasoline car fires.

That said, if I needed a car, I'd still go for an electric one, I'd just not park it in a garage directly connected to a home and certainly not in some basement garage.

[1] https://koka-shop.de/universal-sprinklerkopf-brandschutz.htm...

> With a gasoline car, dump water and foam onto the wreck and that's it

Well yes, but you need a lot of water. Fuel fires are not something you can tackle with a domestic hose.

However as you point out, normally the reason for a battery fire is because it's shorted, so its not/less oxygen dependent.

> Fuel fires are not something you can tackle with a domestic hose.

Tackle and extinguish, no. Keep in check long enough to prevent serious damage until the firefighters come in with the big pumps and hoses? Yes.

People with ebikes generally charge a .5kwh-1kwh battery indoors every day. Any spare batteries after the initial bike purchase come from Amazon. At that energy density, is there any point to trying to contain a potential fire by, say, setting the battery inside a dutch oven? Or on a stack of sheet rock? Or would it burn well-past hot enough to ignite things outside it?

(edit: Dutch Oven has some thermal mass, but too much heat conductivity. Luckily, there is an actual product for this: UL-rated battery storage/charging boxes)

Battery fires produce highly toxic gases. If you’re doing anything to a combusting battery other than running away, then your priorities are wrong.

Right; a battery box isn't for throwing a battery in after it starts combusting; it's for putting it in every time when you charge it, so you don't burn down the entire apartment building while running away.

If you want to contain it a bit and you don't have a metal-fire extinguisher, dump a bucket of sand or fine salt over it. Commercial metal-fire extinguishers are nothing more than a dozen kilograms of dry, fine salt and a special low-pressure nozzle that allows depositing a "layer" of salt on the burning metal fire that melts and thus contains the fire. However it's hard to keep dry enough that it doesn't aggregate over time, reducing the effectiveness.

Personally, I recommend anyone charging serious amounts of unprotected or questionably protected lithium cells in a residential structure to, first of all, not charge them while you are asleep, and to keep a 10-20 liter bucket of sand nearby. Throw it on the burning battery if you can (you should be able to hear the battery go off maybe 30 seconds before it does go off), then run for your life.

The gas tank doesn't have its own ignition source and oxygen built right into the fuel storage area like a battery does. Leaking gas doesn't all but guarantee a fire the way leaking electrons do.

Don't you remember the fire triangle from grade school?

Gasoline in a tank does not burn. Some welders will even weld a tank full of gasoline - it is a safe operation (most welders will refuse to do this, but a few will). The only time a tank of gasoline is a worry is when there are only a few drops in the tank.

The above is simple chemistry, the Stoichiometric air fuel ratio for gasoline has a very narrow range where it will burn. A tank of gasoline will be above this and thus not burn.

Code in what jurisdiction and for what application?

yes exactly we didn't want to firewall the entire garage so I built a structure around the battery.

A bunch of drywall around it?

i would have had to drywall the entire garage (which is pretty large) including ceiling in 3/4" fire-rated stuff which is a lot heavier. What a pain. So I just walled right around the battery a little closet instead.

5x more usable energy. Energy density of Li-ion cells improve by couple digits or so? if set on fire in expendable mode, if I'm skimming this[1] right.

1: https://www.sciencedirect.com/science/article/pii/S037877532...

Unless I missed it, the paper didn't indicate what the battery chemistry breakdown of the data set was. If it is heavily weighted for Sonnen (German home backup battery manufacturer) batteries, then those have always used Lithium Iron Phosphate (LFP) chemistry, which has much lower thermal risk.

In contrast, most historical home backup batteries sold in the US have been early generation Tesla Powerwalls, which are Lithium ion batteries and thus inherently more thermally risky (they must have active cooling systems [1] inherited from Tesla's cars).

Most home batteries currently sold (Enphase, Tesla, etc) now use LFP, so the thermal risk going forward for new installations should be significantly lower.

1. https://wanakasolar.com/knowledge-hub-posts/tesla-powerwall-...

Does anyone know what they’re referring to when citing the risk of fire as similar to that of “tumblers”? Is this a euphemism for clothes driers? My first thought was rock tumblers, but surely they’re not common enough to be statistically significant in determining risks for house fires….

I would assume so. Tumblers are known for causing fires (hot air and dust due to not good cleaning by owners).

Many years ago I got to see a neighbor’s tumble dryer on fire. He’d dragged it out onto his driveway and let it burn. No fire extinguisher apparently. Had this been a battery fixed to his wall, he’d have lost his house.

My main concern with HSS is actually not accidental fires.

Instead, the HSS are usually all connected to the internet and receive closed-source updates. So if a malevolent actor were able to hack into one of these companies (and affect the updates) he could probably cause overheating and/or fires in all connected HSS.

Of course, the damage would be multiplied by the fact that all fires would start simultaneously.

Any opinions on this?

It's not just possible, but highly likely to occur in the near future. What if the company folds and there is a bug that causes it to halt and catch fire? What stops a RAM/ROM bit flipping?

Connected HSS is fundamentally a problem, not unlike IoT. I have several UPS's and not once did I think this might occur, because they are simply not attached to my network in any way. The triggers are based in hardware with a small microcontroller and are unlikely to fail.

Systems that run for long periods and could cause damage should be developed differently. Core safety features should be hardware-based, you shouldn't be able to hack it and make it do something dangerous. If it has to be network connected it should be defensively designed.

I may be wrong but I think battery protection does not rely on firmware, it may even be analog. There are ICs dedicated to this task, that are cheap and effective.

A malicious firmware update can increase battery wear, but it is unlikely to cause a fire.

There are some specific requirements here in AU/NZ for battery home storage, AS/NZ 5139 2019, and I think another update last year. In short, cant be in the way of or next to an egress, window, or door. Cant be in a habitable space or other enclosed area like attic, roof, wall, or crawlspace. If near habitable space it must have fire resistant material (cement board, steel, etc) between the two and 0.6-1m around the battery. An overview https://www.evergreenelectrical.com.au/blog/best-location-so...

We had a home near us in the last decade where the propane tank exploded. I don't know the details, there are a lot of things that go into something like that happening, but one of the things found during the investigation was that, per the building code, the propane tank was too close to the house.

The news went on to say that some non-trivial percentage of residential propane tanks were positioned in a way that wasn't up to code. Because most manufactured homes don't have traditional financing, they aren't subject to the same code inspections, yadda yadda, house goes boom.

The risk of a fire with a home battery system might be lower, but the outcome is an unknown. I've had engines and stoves and fryers and furnaces and chimneys start on fire on me. I know how to deal with those things, even if they are scary. A battery fire, I have no idea how to deal with. Coupled with code standards that are probably not as mature as they should be, and may not see the enforcement they should, and I am content to wait.

For above ground tanks, minimum distance from structure according to NFPA 58:

No restriction for tanks < 125 gallons

10 feet for tanks 125 - 500 gallons

25 feet for tanks 1,000 - 2,000 gallons

A summary here: https://www.cfins.com/wp-content/uploads/2021/11/Propane-Con...

> A battery fire, I have no idea how to deal with

If its a small battery, like any other fire.

But you also need a generator to go with that propane tank. And that generator has quite a few code restrictions, too.

Only if using the propane for power. Parent talked about manufactured homes and non-traditional financing, I would be hazard they are talking about single and double wide trailers. In this case, the propane would most likely be used for heating and cooking.

Is NFPA 58 law?

There are counties in the US that don't even have staffed building permits.

In some places. In others it isn't law, but your insurance company will put it in the contract and so the courts will side with the insurance company denying claims if you violate it. Some places have a different law, and some insurance companies have different things in their contract.

You’ve had 5+ separate spontaneous house fires? That sounds very unlucky.

Probably more than that. Grew up with a wood fireplace, work with a lot of farm equipment, do a lot of stupid things.

Why does "traditional financing" or otherwise make any difference to code requirements or inspections?

Because banks don't want your house to burn down and insurance to refuse to pay out - if that happens almost everyone will declare bankruptcy and the bank is then out the money they loaned on the house. Thus banks will do some checking before letting you get a loan. When you buy a house the fine print (several pages of it which you are supposed to read before you sign) will say things like this because the bank demands it.

House near where I grew up also had a tank explode. All brick house even internal walls.

Completely levelled the thing.

Suspect the tank was indoors though (was a gold smith dude)

Most likely a water heater. Those explode and can level a house. Propane tanks are almost impossible to make explode - though a leak may start an explosion it typically isn't actually the tank.

If he was a goldsmith, I would assume oxygen and acetylene tanks as they are often used in jewellery making but water heaters are also known to explode.

> per the building code, the propane tank was too close to the house.

I doubt that was a material contribution. It's hard to make inside go boom when the fuel is dumping outside except by freak circumstances (bowl shaped property, wind shadow putting a slight vacuum on the structure, etc).

I don't think it's a serious study to count the fire incidents in a single year (2023) and then use it as a generally valid statistic for an entire product category.

Firstly, the interval is too short, whereas other product categories have many years, if not decades, of statistics. For low probability events, counting in too short a time frame can significantly distort the statistics.

Secondly, household battery systems are all relatively new. Similarly, EVs are a recent phenomenon. Is it not reasonable to expect that the chemicals, and hence the safety, of these batteries will degrade over time, so that the fire hazard will increase over time? And if so, counting incidents only for newly installed systems is obviously biased.

And third, are all household storage systems the same in general design and chemical composition? If not, then lumping them together is unlikely to be very helpful in understanding the relative safety of the product category.

On a different note, there's been a LOT of e-bike battery fires, so that's why with designers and engineers in France we've spent some time designing a battery casing that efficiently contains explosions and flames, to safeguard your home, you can check it here if interested! (it's also a repairable battery, so it saves CO2 compared to a standard battery over the long term)

https://www.indiegogo.com/projects/infinite-the-repairable-u...

apples to apples , would be to compare all domestic electrical risks, especialy accidents involving serious injury and fatalities,over time. There is going to be a significant drop in serious accidents after the introduction of breakers and gfi's ,vs, when there were only fuses, and all to often the fuses were replaced with a copper penny. And they were two wire with no neutral.So two different appliences could be reverse grounded in the same area, bad bad budaboom. So in these kinder ,ha!, more grounded times, its likely that total risk is still going down, as older legacy wireing is replaced. There is still many thousands of miles of tube and knob wireing, still carrying current. With.a significant rise in the proportion of transportation, bieng converted to electrical power, there will be an increase in "electrical" accidents, but I think that ,if that was compared to the accidents occuring now with gasoline powered transport, again the numbers will be falling. Gasoline is nasty, dangerous stuff, which is very similar to the electrolite in lithium batteries, except that there is much much more of it around....anf I have yet to see comparisons done, based on actual total accident rates, to the point that ,there is never any mention of the total gasoline fires.

Ngl those videos of scooters catching fire in elevators kinda spooked me about lith tech in general.

Hoping sodium becomes more common but I gather thats not hugely likely due to chemistry diffs

I don’t know anything about sodium based batteries but sodium itself is a serious fire danger. Sodium is explosive in water, more so than lithium I believe.

Pure sodium, yes. Sodium mixtures, usually not; table salt is fairly inert.

So it depends entirely on the chemistry.

That’s true for basically any element including lithium

It should be noted that it is a preprint of a paper that is not peer reviewed. I would wait a bit for a peer reviewed paper.

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

Doesn't people that have money to buy premium electric cars also live in more modern homes? At least in better homes.

Electric car is no longer a premium.

As much as I would love to agree, this is just objectively not true.

Halfway decent used BEVs are super rare and usually expensive, so new remains to only viable option for most. And buying a new car to begin with is a huge premium.

And while prices have been steadily declining for BEVs, in most instances a somewhat comparable ICE car is still cheaper to buy.

Wether or not that is the case for actually maintaining the vehicle heavily depends on electricity and fuel prices where you live. Considering the article is from Germany, take it as an example. Most people do not live in single family homes, but apartments. Most apartments still don’t have a spot for EV charging, so you have to rely on public chargers. They run from anywhere to 35ct/kWh to 60ct/kWh depending on location and charging method.

These should be stuck in a temperature controlled outdoor pit, zoned for small skid steer access, and covered with a metal or reinforced concrete lid to vent smoke away from people.

All lithium batteries fail eventually, and sometimes catastrophically. Planning for safe and easy maintenance should be part of the solution. =3

> 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. The results show a significantly lower probability of an HSS fire compared to a general house fire.

Seems legit.

yep

also:

> the findings indicate that the probability of an HSS fire is very low (0.0049 %) and is 50 times lower than for a general house fire.

So for every 50 "normal" house fires, one extra will be due to HSS.

The bigger question is, what are the consequences of such fires? Looking at burning electric cars, that can't be put out, having burning batteries in an apartment building basement doesn't really seem that fun.

Battery fires are highly toxic. You’ll need to evacuate the area, and cleaning up afterwards might be fun.

I had thought that if I went all-in on a battery system for the home it would ideally be in a cinder-block structure some 50 feet or so from the house — perhaps even below ground.

I'm not sure if people are doing or considering such a thing, if it would be effective.

If Tesla's Powerwall's are so safe, why does the legal agreement to buy one absolve them of all responsibility if there is a fire? This is what has been preventing me from considering buying one in Vermont.

Shouldn't home batteries be lithium iron phosphate and not lithium ion, and thus almost a zero fire hazard? At least as far as cell chemistry goes...electricity is always a fire hazard if discharged incorrectly.

They should, but quite a few are still NMC chemistry.

Like most deployed Tesla Powerwalls only most recent is LFP.

LFP has different full/empty voltages so chips and boards has to be re-made. Unless mandated or made comparatively economical, manufacturers won't switch out infrastructures overnight.

> HSS share roughly the same probability of catching fire as tumblers

Does "tumblers" in this context mean tumbler dryer? I've only ever heard tumbler meaning the type of cup.

Isn't there some recency bias in this, considering home battery backups are relatively new tech (at scale), and the other measures of fire risk are millennia old?

Unless I missed something, it seems to me that the article relays on a substantial lack of actual data.

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