6 ms·

Fire hazard of WHY2025 badge due to 18650 Li-Ion cells

107 points by fjfaase 1y ago

fjfaase 1y ago
[flagged]
- jon-wood 1y ago
  Please don't post LLM summaries without any additional context. If I wanted one I'd ask my nearest LLM for it.
  - fjfaase 1y ago
    Sorry, but I was not aware that the text with the submit (which I wanted to keep short) appears as a comment, otherwise, I would have given more details or left it out.
    - jon-wood 1y ago
      Fair enough, I didn't realise you were the original poster and that's what happened.
  - mtlynch 1y ago
    You're replying to the author/submitter of the post. I don't think this is LLM-generated.
bravetraveler 1y ago
That's a lot of juice for a trinket. Shorted a 'mitigated' battery of these in a charger once, was enough to reconsider vaping entirely
- pjc50 1y ago
  Given how much torch you can power off one of these, I'm not clear why you'd need two of them for a badge, since any conceivable use for that much current is going to start heating up the badge PCB fairly quickly. They're usually sized for >1A each, and you can get >10A off them for short periods, which is very lively for a badge pinned to flammable clothing.
  - arghwhat 1y ago
    Assuming decent cells with low ESR (say, <30mOhm), one such cell will deliver hundreds of amps when shorted, making things a little bit more lively than your estimation. :) (A few hundred amps isn't a lot for a shorted battery, but these are tiny cells so that's what you'll get.) Two cells was probably selected for one of: Voltage to avoid boost converters, capacity to avoid having to do extensive power optimization to make it run the whole event, balance to make it hang even off your neck.
    - piva00 1y ago
      Quite oversized amounts of power for 2 ESP32s running, last I measured a ESP32 board I have running it would consume some 120-180mA.
      - arghwhat 1y ago
        That is highly dependent on the exact ESP32 model and current power state. They can use in excess of 500mA with peaks of 800mA, and can easily use >250mA constant at 3.3V. Some draw much more than that. A board with a few bits and bobs on and a single 18650 cell might only last, say, 8 hours on a charge. Now, a well optimized board with a low-power ESP32 and proper use of sleep states would make that number go from 8 hours to over a week, but that does take a lot of extra effort and may not be worth it over just slapping on another cell.
      - phire 1y ago
        2 ESPs and a 4” color LCD screen (and a keyboard). Depending on how bright the backlight was, that could eat through battery. And if they were using the wifi for any active communication, that increases power too. I suspect they wanted it to last the entire weekend with the display always on. The original design probably only had one cell (maybe even smaller battery with built-in protection) and they hurriedly switched to two 18650 cells at the last moment. They probably went with parallel because that seemed easier, no need to switch to another voltage regulator and charge controller.
    - farhaven 1y ago
bsder 1y ago
> The WHY2025 badge was designed to be powered by 2 Li-Ion 18650 battery cells connected in parallel. Wait, what? I was under the impression that Lithium batteries were really difficult to put in parallel without a LOT of engineering work. The discharge curve for Lithium batteries is super flat. If you put them in parallel, even a small differential between the two means that one battery will completely discharge simply trying to bring the voltage of the other up to match. This is very different from the discharge curve from alkaline which has a nice slope and the batteries can equalize without burning up very much of their capacity. These don't look like they're matched in any way. The connection between them doesn't like very big--I suspect a non-trivial voltage drop if one battery tries to empty into the other. If you need the power, it's much better to put them in series and use a buck converter to bring the final value where you want it. This seems more like a fundamental engineering flaw rather than a fault in the boards (although, to be fair, the creepage and clearance don't look great).
- exmadscientist 1y ago
  Li-Ion chemistry is pretty happy with 1S2P configurations. (That doesn't necessarily mean you should do it.) 2S1P is where the fun starts.
- rollulus 1y ago
  It’s what I thought as well, but I’m not too much into electronics to hold an opinion. It looks like there’s a balancing resistor between them: https://gitlab.com/why2025/team-badge/Hardware/-/blob/main/Carrier/pdf/badgeCarrierCard.pdf https://gitlab.com/why2025/team-badge/Hardware/-/blob/main/C...
  - bsder 1y ago
    With floating grounds due to those MOSFETS adding 50 milliohms or so (on the order of the internal resistance of the batteries!)! YIKES!
    - eqvinox 1y ago
      Putting the protection circuit* on the battery's negative pole is standard best practice (due to NMOS efficiency, and it not being a problem in the slightest), and the 50mΩ actually improves balancing. Please avoid making comments like this based on half knowledge. [*] I do wish it were an actual full protection circuit. It isn't. Then again a run of the mill protection circuit commonly doesn't cover reversed polarity [between protector and cell], which is rather important for this specific appliation.
exmadscientist 1y ago
> The WHY2025 badge was designed to be powered by 2 Li-Ion 18650 battery cells connected in parallel. The cells provided to visitors are of the "unprotected" kind ...I am going to put on my "client-facing consultant" hat for a moment, which means skipping the expletives, and just say that not only is this a Very Bad Design, it is such a Very Bad Design that someone should really have noticed this and not let it happen. Because this really is a Startlingly Bad Idea.
- fjfaase 1y ago
  An earlier design by Badge.Team [1] did not use these cells and Badge.Team (no longer associated with WHY2025) strongly advised against the use of these cells. The earlier design has been matured into Konsool [2] and is available as Tanmatsu [3]. [1] https://badge.team/ https://badge.team/ [2] https://badge.team/docs/badges/konsool/ https://badge.team/docs/badges/konsool/ [3] https://nicolaielectronics.nl/tanmatsu/ https://nicolaielectronics.nl/tanmatsu/
  - stavros 1y ago
    Why was that advice ignored?
    - eqvinox 1y ago
      WHY2025 orga has been a shitshow on the social & interpersonal level. The badge team was one of the casualties. (And triggers, from what I've heard they weren't paragons either, but that's even more hearsay.) (Source: I'm in c3noc/Internetmanufaktur, though not attending WHY. TBH I saw the shitshow coming and decided I don't need it in my life.)
      - slashink 1y ago
        "WHY2025 orga has been a shitshow on the social & interpersonal level." Curious to learn more as an outsider if you don't mind elaborating?
slacktivism123 1y ago
What's with the mock-security-advisory with logo for the 'vulnerability' (Heartbleed, anyone?) Why is the important safety advice buried in a bunch of interpersonal drama and administrivia?
- Juerd 1y ago
  Author here. I didn't add the logo, but it's a wiki so others can theoretically change things. I think the logo is cute though, so let's keep it. I think it was made with the WHY2025 logo generator at https://design.why2025.org/ https://design.why2025.org/
eqvinox 1y ago
I'm confused that noone is pointing out most protected 18650 cells won't even fit in those holders, since protected cells are generally in the 18690…18700 pseudo size range. That's too long to get into those holders. Source: the holders are likely Keystone 1042 [https://www.keyelco.com/product.cfm/product_id/918 https://www.keyelco.com/product.cfm/product_id/918], which I've worked with before. For a protected cell, cf. for example https://imrbatteries.com/products/panasonic-ncr18650b-3350mah-4-87a-battery-protected-button-top https://imrbatteries.com/products/panasonic-ncr18650b-3350ma... - note 69.41mm length. [ed.: it's the China equivalent of a Keystone 1042, https://www.lcsc.com/product-detail/C2988620.html https://www.lcsc.com/product-detail/C2988620.html - I can't confirm but am 95% confident a protected cell won't fit; if it would, the hold on an unprotected 18650 cell would be quite loose.]
- supakeen 1y ago
  Sure, that means the idea of using unprotected cells was already there when the holders were selected :)
  - eqvinox 1y ago
    Yeah, I'm just saying, you can't even buy regular protected cells and put them in, because they won't fucking fit. I do think "actual" 18650 protected cells exist, but they would be rare and expensive because you can't build them out of mass manufactured bare 18650 cells (for obvious reasons of where do you put the damn protection circuit.)
    - supakeen 1y ago
      Ah yea then I misunderstood. That's right you can't easily switch out the cells for protected cells yourself :(
    - Zak 1y ago
      The nomenclature, as commonly used isn't precise enough. 18650 means 18x65mm, but "protected 18650" usually means that cell with electronics stuck on the end, which ends up at 68-70mm long. Nobody calls the result "18680" even though that describes it more precisely. There isn't a common cell slightly shorter than 18650 to produce protected cells that fit in every holder designed for 18650. The AA-size (but not AA-voltage!) 14500 often does come in protected versions that are exactly 50mm long, based on 14430 cells.
ryao 1y ago
At work, whenever we design hardware that uses Li-Ion cells, I always discuss safety before we even have done the design work so that we build something that is safe. Why did these guys not do that? Did they only learn about videos of li-ion explosions/fires after design this? By the way, they probably should have used a LiFePo4 chemistry instead. It would not have the same runtime, but it would be much safer in worst case scenarios.
- Zak 1y ago
  The battery would be less likely to enter thermal runaway and explode with LiFePO4, but this level of short circuit risk is still a significant fire hazard. 3.6V / 0.04 Ohms[0] = 90A. [0] https://lygte-info.dk/review/batteries2012/LFP18650%201500mAh%20LiFePO4%20(Violet)%20UK.html https://lygte-info.dk/review/batteries2012/LFP18650%201500mA...
burnt-resistor 1y ago
Why the fuck didn't they just use say 4 safe(r) CR2032s or simply have only +5V USB-C power in? They could've eliminated most of the risk by simply ripping the 18650 holders off the badges and rely on USB power.
- Zak 1y ago
  You are proposing replacing a ~20Wh battery with a 2.8Wh battery. The maximum current draw from button cells is also likely inadequate for the application.
andrewstuart 1y ago
Avoid battery fires: design your boards for alkaline batteries. They’re safer and in many cases just fine for the job - for example a conference badge needs nothing more than alkaline batts. Also, alkaline batteries are not an expensive nightmare to ship.
- burnt-resistor 1y ago
  Rechargeable safe(r) chemistries. Alkaline batteries are insta-e-waste. Like the common form-factors of AA/AAA Ni-MH that are acquirable locally.
  - rgovostes 1y ago
    Conference badges are basically insta-e-waste too.
    - wkat4242 1y ago
      Not the ones from these events they are really well designed (welll... Feature wise) and offer great learning and usage opportunities. This one has a big colour screen and a full qwerty keyboard. It's not really to be used as a badge. More as a way to get people interested in making something cool with it. After all, hacker conferences these days are about 50% traditional security and 50% makers.
  - em3rgent0rdr 1y ago
    AA/AAA won't fit in a flat conference badge. I've wanted to get coin cell format NiMH, but they only seem to be the more thicker button type (or I don't know the magical term to search for), and I can't seem to find cheap options either. The 40 maH ones seem to be 5mm tall and I can't seem to find many smaller capacity ones that are thinner.
    - michaelt 1y ago
      In the badge from the article they're using 18650s, so AA batteries would actually have slimmed it down by 3.5mm. Lower voltage, of course.
charcircuit 1y ago
Hopefully, they get sued to clearly set the precedent that this is not acceptable. Just because it may be a devkit, targeted towards knowledgeable individuals, or amateur made that doesn't mean that they should be distributing unsafe electronics like this because it's cheaper than making a safe version.
- seszett 1y ago
  This is the Netherlands, they obviously (and luckily IMO) won't get sued when there has not even been any incident and they have a clear advisory for the safety problem. I don't even know on what grounds could anyone sue them.
krekr 1y ago
I've also written up some more findings. They can be found at https://www.krekr.nl/content/why2025-badge-fire-hazard-additional-issues/ https://www.krekr.nl/content/why2025-badge-fire-hazard-addit...
1oooqooq 1y ago
fireworks in the badge? take that defcon!
deleted 1y ago
[deleted]
1970-01-01 1y ago
It's all cute fun and nerding out until the room is filled with smoke. The art of one upping your hackercon badges is clearly getting out of control. Good job on calling it out now.
lysace 1y ago
Repost from a previous comment of mine, that sort of applies here: > I get nervous when I see videos of people buying random Li-Ion/Po-battery powered crap from Teemu etc. > My personal policy for buying anything with such a battery: the seller must have a meaningful presence in my country, selling at least like $10M/year. I.e. they need to have a large enough exposure to handle a catastrophic house fire if something happens due to e.g. a bad design. I figure that at around $10M/year they start caring, even if they are psychopaths or incompetent.
ShakataGaNai 1y ago
I love these concept of badges, but almost never are they well executed. Defcon has had TONS of problems with their badges of all types. OpenSauce has tried for the last two years with only middling results. Don't get me wrong, I'm not trying to say "don't do it" or "These people are stupid". It's just that people underestimate the time and effort required. It's basically bringing a product to market, for 20 to 50k people (depending on the event), in a few months time. But it also needs to be "cool" and "unique" and often "beginner friendly" and extremely cheap. Crazy crazy hard.
- Waterluvian 1y ago
  Engineering is the first 80% of work. But productization is the second 80%. I find that the more nerdy a community or product audience, the more the latter suffers.
  - fjfaase 1y ago
    This is right. But this time that was not the primary reason. From earlier experiences, Badge.Team, started well ahead of time and were on schedule, but things went wrong after some drama with the WHY2025 organization.
- richardlblair 1y ago
  It's almost fitting, isn't it? Given what each of these conferences are all about.
- ryukoposting 1y ago
  It's worth noting that this kind of thing works great at a smaller scale. Adafruit has been marketing bare PCBs for sew-on applications for years. On an even smaller scale: I contributed to a beginner soldering class by designing this simple board shaped like the high school's logo: https://postimg.cc/ftwtqHFn https://postimg.cc/ftwtqHFn (for the record, shorts across the contacts in the exposed metal area are harmless. The transistor never saturates in this circuit) The key to Adafruit's arduinos-but-for-cosplay, and my keychain photocell thingy is that neither demands two(!) 18650s worth of power. There just isn't a significant hazard in the first place.
knotimpressed 1y ago
Braving potentially getting spit roasted to ask: If I'm making my own 18650 USB C power banks, are there any easy to miss risks? I've got the cells in holders, not welded, but the holders are specc'd above the current I need. The cells are unprotected, but the Aliexpress listing for the power management board says specifically to use unprotected cells, as at 6A draw most protection boards don't do well (dubious). The cells are tested and mechanically protected by a thick enclosure. The only EE work I'm doing is soldering 2 high gauge wires from the holder to the board that's doing everything else. I know Aliexpress isn't a bastion of quality, but the seller has good feedback and I checked over the board to make sure there's at the very least a good counterfeit battery protection IC included. Currently, the concerns I have are: - the holder relies on good contact to deliver 6A without developing hotspots on the terminals - the board from Aliexpress perhaps should not be trusted If there's anything else anyone can think of, I'm happy to hear it.
- Eduard 1y ago
  it helps if you give us links and model numbers
  - knotimpressed 1y ago
    Well, there’s only one real part (the cells are interchangeable, and reclaimed) https://a.aliexpress.com/_mKNNnGZ https://a.aliexpress.com/_mKNNnGZ I’ve gone with the purple C and U model.
- Cyan488 1y ago
  As an electronics designer myself, I would find it hard to trust the AliExpress board. Without the design files, running a failure modes and effects analysis on the board is difficult. There's also no guarantee that each board you get is built identically. Some parts or the whole design could be changed between orders. If I was designing a power bank board professionally, I'd be putting it through the ringer - environmental, mechanical, component level short circuit, load short circuit, load power injection, input over-voltage, input transient, RFI/EMI susceptibility, etc. Do you trust that all that has been done on a board that is representative of what you've received?
aetherspawn 1y ago
Lithium is the wrong chemistry for this novelty throwaway thing. Risks of fire all along the supply and disposal chain. They could just use a few watch cells. LEDs use no power at all, so lithium not required; and watch cells aren’t hazardous when shorted. Even the form factor of 18650 seems wrong for this, they would be so bulky compared to watch cells or AAA cells.
- stonogo 1y ago
  Watch cells are also usually lithium. I'd have just gone with LiFePO4 18650 cells.
  - amluto 1y ago
    Huh? A little CR2032 or similar cell has minimal short circuit current. A LiFePO4 18650 may not set itself on fire if shorted, but it could still set the rest of the badge or your shirt on fire.
  - aetherspawn 1y ago
    That doesn’t solve the issue because the fire risk is due to short circuit. Any battery that is Li-based has too low IR to self limit.
- mfitzp 1y ago
  The “badge” has a 2.8'' TFT screen, not just a couple of LEDs.
squarefoot 1y ago
Most if not all holders I worked with simply can't hold protected cells, which I find shortsighted and stupid as making receptacles and spring contacts that can hold both would be dead easy, but I guess saving fractions of pennies with less plastic, metal and weight is the priority.

107 points by fjfaase 1y ago

fjfaase 1y ago

[flagged]

jon-wood 1y ago
Please don't post LLM summaries without any additional context. If I wanted one I'd ask my nearest LLM for it.
- fjfaase 1y ago
  Sorry, but I was not aware that the text with the submit (which I wanted to keep short) appears as a comment, otherwise, I would have given more details or left it out.
  - jon-wood 1y ago
    Fair enough, I didn't realise you were the original poster and that's what happened.
- mtlynch 1y ago
  You're replying to the author/submitter of the post. I don't think this is LLM-generated.

bravetraveler 1y ago

That's a lot of juice for a trinket. Shorted a 'mitigated' battery of these in a charger once, was enough to reconsider vaping entirely

pjc50 1y ago
Given how much torch you can power off one of these, I'm not clear why you'd need two of them for a badge, since any conceivable use for that much current is going to start heating up the badge PCB fairly quickly. They're usually sized for >1A each, and you can get >10A off them for short periods, which is very lively for a badge pinned to flammable clothing.
- arghwhat 1y ago
  Assuming decent cells with low ESR (say, <30mOhm), one such cell will deliver hundreds of amps when shorted, making things a little bit more lively than your estimation. :) (A few hundred amps isn't a lot for a shorted battery, but these are tiny cells so that's what you'll get.) Two cells was probably selected for one of: Voltage to avoid boost converters, capacity to avoid having to do extensive power optimization to make it run the whole event, balance to make it hang even off your neck.
  - piva00 1y ago
    Quite oversized amounts of power for 2 ESP32s running, last I measured a ESP32 board I have running it would consume some 120-180mA.
    - arghwhat 1y ago
      That is highly dependent on the exact ESP32 model and current power state. They can use in excess of 500mA with peaks of 800mA, and can easily use >250mA constant at 3.3V. Some draw much more than that. A board with a few bits and bobs on and a single 18650 cell might only last, say, 8 hours on a charge. Now, a well optimized board with a low-power ESP32 and proper use of sleep states would make that number go from 8 hours to over a week, but that does take a lot of extra effort and may not be worth it over just slapping on another cell.
    - phire 1y ago
      2 ESPs and a 4” color LCD screen (and a keyboard). Depending on how bright the backlight was, that could eat through battery. And if they were using the wifi for any active communication, that increases power too. I suspect they wanted it to last the entire weekend with the display always on. The original design probably only had one cell (maybe even smaller battery with built-in protection) and they hurriedly switched to two 18650 cells at the last moment. They probably went with parallel because that seemed easier, no need to switch to another voltage regulator and charge controller.
  - farhaven 1y ago

bsder 1y ago

> The WHY2025 badge was designed to be powered by 2 Li-Ion 18650 battery cells connected in parallel. Wait, what? I was under the impression that Lithium batteries were really difficult to put in parallel without a LOT of engineering work. The discharge curve for Lithium batteries is super flat. If you put them in parallel, even a small differential between the two means that one battery will completely discharge simply trying to bring the voltage of the other up to match. This is very different from the discharge curve from alkaline which has a nice slope and the batteries can equalize without burning up very much of their capacity. These don't look like they're matched in any way. The connection between them doesn't like very big--I suspect a non-trivial voltage drop if one battery tries to empty into the other. If you need the power, it's much better to put them in series and use a buck converter to bring the final value where you want it. This seems more like a fundamental engineering flaw rather than a fault in the boards (although, to be fair, the creepage and clearance don't look great).

exmadscientist 1y ago
Li-Ion chemistry is pretty happy with 1S2P configurations. (That doesn't necessarily mean you should do it.) 2S1P is where the fun starts.
rollulus 1y ago
It’s what I thought as well, but I’m not too much into electronics to hold an opinion. It looks like there’s a balancing resistor between them: https://gitlab.com/why2025/team-badge/Hardware/-/blob/main/Carrier/pdf/badgeCarrierCard.pdf https://gitlab.com/why2025/team-badge/Hardware/-/blob/main/C...
- bsder 1y ago
  With floating grounds due to those MOSFETS adding 50 milliohms or so (on the order of the internal resistance of the batteries!)! YIKES!
  - eqvinox 1y ago
    Putting the protection circuit* on the battery's negative pole is standard best practice (due to NMOS efficiency, and it not being a problem in the slightest), and the 50mΩ actually improves balancing. Please avoid making comments like this based on half knowledge. [*] I do wish it were an actual full protection circuit. It isn't. Then again a run of the mill protection circuit commonly doesn't cover reversed polarity [between protector and cell], which is rather important for this specific appliation.

exmadscientist 1y ago

> The WHY2025 badge was designed to be powered by 2 Li-Ion 18650 battery cells connected in parallel. The cells provided to visitors are of the "unprotected" kind ...I am going to put on my "client-facing consultant" hat for a moment, which means skipping the expletives, and just say that not only is this a Very Bad Design, it is such a Very Bad Design that someone should really have noticed this and not let it happen. Because this really is a Startlingly Bad Idea.

fjfaase 1y ago
An earlier design by Badge.Team [1] did not use these cells and Badge.Team (no longer associated with WHY2025) strongly advised against the use of these cells. The earlier design has been matured into Konsool [2] and is available as Tanmatsu [3]. [1] https://badge.team/ https://badge.team/ [2] https://badge.team/docs/badges/konsool/ https://badge.team/docs/badges/konsool/ [3] https://nicolaielectronics.nl/tanmatsu/ https://nicolaielectronics.nl/tanmatsu/
- stavros 1y ago
  Why was that advice ignored?
  - eqvinox 1y ago
    WHY2025 orga has been a shitshow on the social & interpersonal level. The badge team was one of the casualties. (And triggers, from what I've heard they weren't paragons either, but that's even more hearsay.) (Source: I'm in c3noc/Internetmanufaktur, though not attending WHY. TBH I saw the shitshow coming and decided I don't need it in my life.)
    - slashink 1y ago
      "WHY2025 orga has been a shitshow on the social & interpersonal level." Curious to learn more as an outsider if you don't mind elaborating?

slacktivism123 1y ago

What's with the mock-security-advisory with logo for the 'vulnerability' (Heartbleed, anyone?) Why is the important safety advice buried in a bunch of interpersonal drama and administrivia?

Juerd 1y ago
Author here. I didn't add the logo, but it's a wiki so others can theoretically change things. I think the logo is cute though, so let's keep it. I think it was made with the WHY2025 logo generator at https://design.why2025.org/ https://design.why2025.org/

eqvinox 1y ago

I'm confused that noone is pointing out most protected 18650 cells won't even fit in those holders, since protected cells are generally in the 18690…18700 pseudo size range. That's too long to get into those holders. Source: the holders are likely Keystone 1042 [https://www.keyelco.com/product.cfm/product_id/918 https://www.keyelco.com/product.cfm/product_id/918], which I've worked with before. For a protected cell, cf. for example https://imrbatteries.com/products/panasonic-ncr18650b-3350mah-4-87a-battery-protected-button-top https://imrbatteries.com/products/panasonic-ncr18650b-3350ma... - note 69.41mm length. [ed.: it's the China equivalent of a Keystone 1042, https://www.lcsc.com/product-detail/C2988620.html https://www.lcsc.com/product-detail/C2988620.html - I can't confirm but am 95% confident a protected cell won't fit; if it would, the hold on an unprotected 18650 cell would be quite loose.]

supakeen 1y ago
Sure, that means the idea of using unprotected cells was already there when the holders were selected :)
- eqvinox 1y ago
  Yeah, I'm just saying, you can't even buy regular protected cells and put them in, because they won't fucking fit. I do think "actual" 18650 protected cells exist, but they would be rare and expensive because you can't build them out of mass manufactured bare 18650 cells (for obvious reasons of where do you put the damn protection circuit.)
  - supakeen 1y ago
    Ah yea then I misunderstood. That's right you can't easily switch out the cells for protected cells yourself :(
  - Zak 1y ago
    The nomenclature, as commonly used isn't precise enough. 18650 means 18x65mm, but "protected 18650" usually means that cell with electronics stuck on the end, which ends up at 68-70mm long. Nobody calls the result "18680" even though that describes it more precisely. There isn't a common cell slightly shorter than 18650 to produce protected cells that fit in every holder designed for 18650. The AA-size (but not AA-voltage!) 14500 often does come in protected versions that are exactly 50mm long, based on 14430 cells.

ryao 1y ago

At work, whenever we design hardware that uses Li-Ion cells, I always discuss safety before we even have done the design work so that we build something that is safe. Why did these guys not do that? Did they only learn about videos of li-ion explosions/fires after design this? By the way, they probably should have used a LiFePo4 chemistry instead. It would not have the same runtime, but it would be much safer in worst case scenarios.

Zak 1y ago
The battery would be less likely to enter thermal runaway and explode with LiFePO4, but this level of short circuit risk is still a significant fire hazard. 3.6V / 0.04 Ohms[0] = 90A. [0] https://lygte-info.dk/review/batteries2012/LFP18650%201500mAh%20LiFePO4%20(Violet)%20UK.html https://lygte-info.dk/review/batteries2012/LFP18650%201500mA...

burnt-resistor 1y ago

Why the fuck didn't they just use say 4 safe(r) CR2032s or simply have only +5V USB-C power in? They could've eliminated most of the risk by simply ripping the 18650 holders off the badges and rely on USB power.

Zak 1y ago
You are proposing replacing a ~20Wh battery with a 2.8Wh battery. The maximum current draw from button cells is also likely inadequate for the application.

andrewstuart 1y ago

Avoid battery fires: design your boards for alkaline batteries. They’re safer and in many cases just fine for the job - for example a conference badge needs nothing more than alkaline batts. Also, alkaline batteries are not an expensive nightmare to ship.

burnt-resistor 1y ago
Rechargeable safe(r) chemistries. Alkaline batteries are insta-e-waste. Like the common form-factors of AA/AAA Ni-MH that are acquirable locally.
- rgovostes 1y ago
  Conference badges are basically insta-e-waste too.
  - wkat4242 1y ago
    Not the ones from these events they are really well designed (welll... Feature wise) and offer great learning and usage opportunities. This one has a big colour screen and a full qwerty keyboard. It's not really to be used as a badge. More as a way to get people interested in making something cool with it. After all, hacker conferences these days are about 50% traditional security and 50% makers.
- em3rgent0rdr 1y ago
  AA/AAA won't fit in a flat conference badge. I've wanted to get coin cell format NiMH, but they only seem to be the more thicker button type (or I don't know the magical term to search for), and I can't seem to find cheap options either. The 40 maH ones seem to be 5mm tall and I can't seem to find many smaller capacity ones that are thinner.
  - michaelt 1y ago
    In the badge from the article they're using 18650s, so AA batteries would actually have slimmed it down by 3.5mm. Lower voltage, of course.

charcircuit 1y ago

Hopefully, they get sued to clearly set the precedent that this is not acceptable. Just because it may be a devkit, targeted towards knowledgeable individuals, or amateur made that doesn't mean that they should be distributing unsafe electronics like this because it's cheaper than making a safe version.

seszett 1y ago
This is the Netherlands, they obviously (and luckily IMO) won't get sued when there has not even been any incident and they have a clear advisory for the safety problem. I don't even know on what grounds could anyone sue them.

krekr 1y ago

I've also written up some more findings. They can be found at https://www.krekr.nl/content/why2025-badge-fire-hazard-additional-issues/ https://www.krekr.nl/content/why2025-badge-fire-hazard-addit...

1oooqooq 1y ago

fireworks in the badge? take that defcon!

deleted 1y ago

[deleted]

1970-01-01 1y ago

It's all cute fun and nerding out until the room is filled with smoke. The art of one upping your hackercon badges is clearly getting out of control. Good job on calling it out now.

lysace 1y ago

Repost from a previous comment of mine, that sort of applies here: > I get nervous when I see videos of people buying random Li-Ion/Po-battery powered crap from Teemu etc. > My personal policy for buying anything with such a battery: the seller must have a meaningful presence in my country, selling at least like $10M/year. I.e. they need to have a large enough exposure to handle a catastrophic house fire if something happens due to e.g. a bad design. I figure that at around $10M/year they start caring, even if they are psychopaths or incompetent.

ShakataGaNai 1y ago

I love these concept of badges, but almost never are they well executed. Defcon has had TONS of problems with their badges of all types. OpenSauce has tried for the last two years with only middling results. Don't get me wrong, I'm not trying to say "don't do it" or "These people are stupid". It's just that people underestimate the time and effort required. It's basically bringing a product to market, for 20 to 50k people (depending on the event), in a few months time. But it also needs to be "cool" and "unique" and often "beginner friendly" and extremely cheap. Crazy crazy hard.

Waterluvian 1y ago
Engineering is the first 80% of work. But productization is the second 80%. I find that the more nerdy a community or product audience, the more the latter suffers.
- fjfaase 1y ago
  This is right. But this time that was not the primary reason. From earlier experiences, Badge.Team, started well ahead of time and were on schedule, but things went wrong after some drama with the WHY2025 organization.
richardlblair 1y ago
It's almost fitting, isn't it? Given what each of these conferences are all about.
ryukoposting 1y ago
It's worth noting that this kind of thing works great at a smaller scale. Adafruit has been marketing bare PCBs for sew-on applications for years. On an even smaller scale: I contributed to a beginner soldering class by designing this simple board shaped like the high school's logo: https://postimg.cc/ftwtqHFn https://postimg.cc/ftwtqHFn (for the record, shorts across the contacts in the exposed metal area are harmless. The transistor never saturates in this circuit) The key to Adafruit's arduinos-but-for-cosplay, and my keychain photocell thingy is that neither demands two(!) 18650s worth of power. There just isn't a significant hazard in the first place.

knotimpressed 1y ago

Braving potentially getting spit roasted to ask: If I'm making my own 18650 USB C power banks, are there any easy to miss risks? I've got the cells in holders, not welded, but the holders are specc'd above the current I need. The cells are unprotected, but the Aliexpress listing for the power management board says specifically to use unprotected cells, as at 6A draw most protection boards don't do well (dubious). The cells are tested and mechanically protected by a thick enclosure. The only EE work I'm doing is soldering 2 high gauge wires from the holder to the board that's doing everything else. I know Aliexpress isn't a bastion of quality, but the seller has good feedback and I checked over the board to make sure there's at the very least a good counterfeit battery protection IC included. Currently, the concerns I have are: - the holder relies on good contact to deliver 6A without developing hotspots on the terminals - the board from Aliexpress perhaps should not be trusted If there's anything else anyone can think of, I'm happy to hear it.

Eduard 1y ago
it helps if you give us links and model numbers
- knotimpressed 1y ago
  Well, there’s only one real part (the cells are interchangeable, and reclaimed) https://a.aliexpress.com/_mKNNnGZ https://a.aliexpress.com/_mKNNnGZ I’ve gone with the purple C and U model.
Cyan488 1y ago
As an electronics designer myself, I would find it hard to trust the AliExpress board. Without the design files, running a failure modes and effects analysis on the board is difficult. There's also no guarantee that each board you get is built identically. Some parts or the whole design could be changed between orders. If I was designing a power bank board professionally, I'd be putting it through the ringer - environmental, mechanical, component level short circuit, load short circuit, load power injection, input over-voltage, input transient, RFI/EMI susceptibility, etc. Do you trust that all that has been done on a board that is representative of what you've received?

aetherspawn 1y ago

Lithium is the wrong chemistry for this novelty throwaway thing. Risks of fire all along the supply and disposal chain. They could just use a few watch cells. LEDs use no power at all, so lithium not required; and watch cells aren’t hazardous when shorted. Even the form factor of 18650 seems wrong for this, they would be so bulky compared to watch cells or AAA cells.

stonogo 1y ago
Watch cells are also usually lithium. I'd have just gone with LiFePO4 18650 cells.
- amluto 1y ago
  Huh? A little CR2032 or similar cell has minimal short circuit current. A LiFePO4 18650 may not set itself on fire if shorted, but it could still set the rest of the badge or your shirt on fire.
- aetherspawn 1y ago
  That doesn’t solve the issue because the fire risk is due to short circuit. Any battery that is Li-based has too low IR to self limit.
mfitzp 1y ago
The “badge” has a 2.8'' TFT screen, not just a couple of LEDs.

squarefoot 1y ago

Most if not all holders I worked with simply can't hold protected cells, which I find shortsighted and stupid as making receptacles and spring contacts that can hold both would be dead easy, but I guess saving fractions of pennies with less plastic, metal and weight is the priority.