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

Original Article ↗ Hacker News Discussion ↗

Overall risk comparisons

  • Thread highlights that, per the paper, home storage systems (HSS) and EVs ignite less often than general house fires and ICE vehicles.
  • HSS fire likelihood is likened to clothes dryers/tumble dryers, but commenters stress that fire severity and toxicity can be worse for batteries than for many other causes.

Data and methodology concerns

  • Several comments question robustness:
    • HSS incidents in Germany were collected via web crawling for a single year (2023) due to lack of official data.
    • EVs and HSS are new; failure rates may change as systems age.
    • Battery chemistries and system designs are lumped together.
    • The paper is a preprint, not yet peer-reviewed.
  • Some see the results as directionally reassuring but statistically fragile.

Battery chemistry and design

  • Strong emphasis on differences between lithium iron phosphate (LFP) and other lithium-ion chemistries (e.g., NMC):
    • LFP is repeatedly described as much more fire-resistant and less prone to thermal runaway.
    • Many newer EVs and home batteries (including newer Powerwalls) reportedly use LFP; older systems often did not.
  • Commenters criticize the paper for barely differentiating chemistries.

Fire behavior and firefighting

  • Multiple posts stress that Li‑ion fires are self-sustaining, extremely hot, produce toxic gases, and may re‑ignite.
  • Firefighting strategies discussed: cooling/flooding, isolating packs in sand or water, and sometimes simply letting an EV burn while protecting surroundings.
  • Risk in enclosed spaces (garages, basements, elevators) is seen as particularly concerning.

Codes, installation quality, and placement

  • Germany is portrayed as stricter by default; US enforcement is uneven, with many poor or DIY installations and patchy NEC adoption.
  • Real-world example: a 15 kWh system required a fire-rated “room” and door, adding ~5–10% to battery cost (DIY).
  • Several standards (e.g., AU/NZ) restrict installing batteries in habitable spaces or near egress.
  • Many commenters prefer batteries outside, behind fire-rated barriers, or in standalone structures, but note climate and cost constraints.

Comparisons with other risks

  • Numerical translation: expected intervals (very approximate) like ~360 years between general house fires vs ~20,000 years for HSS in a single dwelling.
  • Some argue battery focus is overblown relative to ICE vehicle fires, gas explosions, and kitchen fires; others counter that even rare lithium fires can be uniquely destructive.

Regulation, standards, and cheap batteries

  • Strong concern about low-quality e‑bike/scooter batteries and chargers, especially in NYC, where they are a leading fire cause.
  • Calls for mandatory UL-equivalent certification and better enforcement, especially on online marketplaces, which are accused of tolerating fake safety markings.
  • Note that UL alone doesn’t guarantee cell quality; pack-level design and prevention of cascading failures matter.

Cyber and IoT concerns

  • Some worry that internet-connected HSS with closed-source firmware could be mass-compromised, inducing simultaneous overcharge/overheat events.
  • Others respond that core protection is typically handled by dedicated hardware/analog ICs, limiting what malicious firmware can do, though it might still increase wear.

User attitudes and practical mitigations

  • Enthusiasts remain interested in solar + storage despite cost and code hassles, often citing climate and resilience.
  • Skeptics are wary of unclear long-term risks, code immaturity, and cleanup/toxicity after a fire.
  • Practical mitigations mentioned: placing batteries in fire-rated closets or outdoors; using fire-rated boxes or even ovens for charging e‑bike packs; avoiding overnight charging; keeping sand nearby for small battery fires.