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I like to do a bit of napkin math when storing batteries. I don't care what the technology or marketing says. Think about it in terms of "A 33kWH battery rough

I like to do a bit of napkin math when storing batteries. I don't care what the technology or marketing says. Think about it in terms of "A 33kWH battery roughly equals 1 gallon of gasoline". This is the most paranoid possible way to look at it, but it does help to establish some perspective. Energy is energy and if you don't really think it through, you may wind up with much worse than LTE modem/router fires. Tesla power walls are an example of something I could never install in my home due to this simple math. I would not be able to sleep at night knowing there is a chance they could go up while bolted to my home. I've got one of those EcoFlow batteries (2kWH) for emergencies, but I keep it on a concrete slab (protected from weather) outside my home. Go look at how a datacenter does their batteries if you want to get a sense of this very same paranoia at scale. All the DC-scale UPS systems I've seen typically consist of gigantic, low voltage cells installed in a manner expressly designed to deal with the worst case. I think the density of the energy is what is most dangerous in my mind. A whole room full of lead acid batteries might not be very portable, but its a hell of a lot easier to inspect room-scale components, prove they are safe, and deal with emergencies before they turn into catastrophes.

fbdab103 3y ago
If I am ever in a scenario where I could have a house-sized battery system, I intend to have a disconnected concrete shed dedicated for storing them. Seems like a simple mitigation which would make me feel significantly better about the situation.
reisse 3y ago
> Think about it in terms of "A 33kWH battery roughly equals 1 gallon of gasoline". This is the most paranoid possible way to look at it, but it does help to establish some perspective. Nah, that's the wrong way to think about it. Oxidation (well, burning) of lithium releases far more energy than the electric charge of the battery. Electric (dis)charge merely gives the initial heat to break structural integrity and set lithium on fire. And even then the problem is not in the amount of energy, but in that it's almost impossible to extinguish a lithium fire. And the fumes from battery are thick and toxic. > I think the density of the energy is what is most dangerous in my mind. A whole room full of lead acid batteries might not be very portable... Nah again. Lead-acid just does not burn so spectacularly. And about the energy density - filled fuel tank of a regular car has much higher energy density than Tesla battery, but is significantly harder to ignite, easier to extinguish, and when burning, releases the energy slower.
- George83728 3y ago
  The worst case scenario with a lead-acid battery is some manner of electrical fault leading to electrolysis in the batteries, releasing hydrogen and oxygen gas which subsequently may cause a very violent explosion. I've never heard of a house blowing up like this, but it has happened with submarines.
  - Tool_of_Society 3y ago
    Long ago a friend's car battery exploded. The car was an early 70s chevy nova so there wasn't much in the way of electrical system to check. Everything was good and the next battery lived +5 years with no changes. Always figured there was some minor defect or something that caused the battery to start emitting hydrogen.
    - briHass 3y ago
      Always wear safety glasses when charging, disconnecting, jump starting, etc. car batteries (lead acid). The small amount of hydrogen generated can ignite from a spark, and it's enough to explode the top and shoot plastic scrapnel everywhere. It won't seriously injure your meatier bits, but it's more than sufficient to take out an eye.
      - robbiep 3y ago
        Your NNT must be seriously huge here
  - shagie 3y ago
    The VAX war - https://www.hactrn.net/sra/vaxen.html https://www.hactrn.net/sra/vaxen.html > VAXen, my children, just don't belong some places. In my business, I am frequently called by small sites and startups having VAX problems. So when a friend of mine in an Extremely Large Financial Institution (ELFI) called me one day to ask for help, I was intrigued because this outfit is a really major VAX user--they have several large herds of VAXen--and plenty of sharp VAXherds to take care of them. > (large skip) > So now the whole data center was dead, sort of. The fire alarm system had it's own battery backup and was still alive. The lead acid storage batteries of the immortal power system had been discharging at a furious rate keeping all those big blue boxes running and there was a significant amount of sulfuric acid vapor. Nothing actually caught fire but the smoke detectors were convinced it had. > The fire alarm klaxon went off and the siren warning of imminent halon gas release was screaming. We started to panic but the data center manager shouted over the din, ``Don't worry, the halon system failed its acceptance test last week. It's disabled and nothing will happen.'' > He was half right, the primary halon system indeed failed to discharge. But the secondary halon system observed that the primary had conked and instantly did its duty, which was to deal with Dire Disasters. It had twice the capacity and six times the discharge rate. > (and it continues)
bityard 3y ago
You might be interested in Lithium iron phosphate batteries which are MUCH safer than the traditional lithium ion batteries you're talking about here.

fbdab103 3y ago

If I am ever in a scenario where I could have a house-sized battery system, I intend to have a disconnected concrete shed dedicated for storing them. Seems like a simple mitigation which would make me feel significantly better about the situation.

reisse 3y ago

> Think about it in terms of "A 33kWH battery roughly equals 1 gallon of gasoline". This is the most paranoid possible way to look at it, but it does help to establish some perspective. Nah, that's the wrong way to think about it. Oxidation (well, burning) of lithium releases far more energy than the electric charge of the battery. Electric (dis)charge merely gives the initial heat to break structural integrity and set lithium on fire. And even then the problem is not in the amount of energy, but in that it's almost impossible to extinguish a lithium fire. And the fumes from battery are thick and toxic. > I think the density of the energy is what is most dangerous in my mind. A whole room full of lead acid batteries might not be very portable... Nah again. Lead-acid just does not burn so spectacularly. And about the energy density - filled fuel tank of a regular car has much higher energy density than Tesla battery, but is significantly harder to ignite, easier to extinguish, and when burning, releases the energy slower.

George83728 3y ago
The worst case scenario with a lead-acid battery is some manner of electrical fault leading to electrolysis in the batteries, releasing hydrogen and oxygen gas which subsequently may cause a very violent explosion. I've never heard of a house blowing up like this, but it has happened with submarines.
- Tool_of_Society 3y ago
  Long ago a friend's car battery exploded. The car was an early 70s chevy nova so there wasn't much in the way of electrical system to check. Everything was good and the next battery lived +5 years with no changes. Always figured there was some minor defect or something that caused the battery to start emitting hydrogen.
  - briHass 3y ago
    Always wear safety glasses when charging, disconnecting, jump starting, etc. car batteries (lead acid). The small amount of hydrogen generated can ignite from a spark, and it's enough to explode the top and shoot plastic scrapnel everywhere. It won't seriously injure your meatier bits, but it's more than sufficient to take out an eye.
    - robbiep 3y ago
      Your NNT must be seriously huge here
- shagie 3y ago
  The VAX war - https://www.hactrn.net/sra/vaxen.html https://www.hactrn.net/sra/vaxen.html > VAXen, my children, just don't belong some places. In my business, I am frequently called by small sites and startups having VAX problems. So when a friend of mine in an Extremely Large Financial Institution (ELFI) called me one day to ask for help, I was intrigued because this outfit is a really major VAX user--they have several large herds of VAXen--and plenty of sharp VAXherds to take care of them. > (large skip) > So now the whole data center was dead, sort of. The fire alarm system had it's own battery backup and was still alive. The lead acid storage batteries of the immortal power system had been discharging at a furious rate keeping all those big blue boxes running and there was a significant amount of sulfuric acid vapor. Nothing actually caught fire but the smoke detectors were convinced it had. > The fire alarm klaxon went off and the siren warning of imminent halon gas release was screaming. We started to panic but the data center manager shouted over the din, ``Don't worry, the halon system failed its acceptance test last week. It's disabled and nothing will happen.'' > He was half right, the primary halon system indeed failed to discharge. But the secondary halon system observed that the primary had conked and instantly did its duty, which was to deal with Dire Disasters. It had twice the capacity and six times the discharge rate. > (and it continues)

bityard 3y ago

You might be interested in Lithium iron phosphate batteries which are MUCH safer than the traditional lithium ion batteries you're talking about here.