[HN Gopher] CT scans of 1k lithium-ion batteries show quality ri...
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CT scans of 1k lithium-ion batteries show quality risks in
inexpensive cells
Author : jonbruner
Score : 104 points
Date : 2025-09-24 19:29 UTC (2 days ago)
(HTM) web link (www.lumafield.com)
(TXT) w3m dump (www.lumafield.com)
| progbits wrote:
| To save everyone the hassle of filling out the "get the report"
| form:
|
| https://7802750.fs1.hubspotusercontent-na1.net/hubfs/7802750...
| nom wrote:
| thank you
| Neywiny wrote:
| I find their table of advertised vs actual capacity to be
| misleadingly negative. They only discharged to 3v. 2.7 could be
| viewed as more standard. 2.5 is not unheard of. For example, the
| vapvell 4000 they said was around 3000. They even have a note
| that says that isn't a reasonable capacity estimate. And yet they
| still put the percentage and the number. As if they've falsely
| advertised. However, if you go to vapcell's graphs on their
| website, it all tracks. Feels out of scope for the report and
| shouldn't have been done
| ricardobeat wrote:
| It even says "Conservative discharge that would not extract
| maximum performance". A lot of electronics built for li-ion
| will not work <3V so it's a perfectly reasonable benchmark,
| especially to show the difference between brands.
| londons_explore wrote:
| A lot of electronics need a 3.3v rail and produce that from a
| linear or buck regulator, so won't work below 3.4 volts.
| Tade0 wrote:
| Battery operated devices, while nominally 3.3V, commonly
| work down to 3V or even 2.7V in line with the voltage curve
| of lithium (not li-ion) coin batteries.
| edgineer wrote:
| I went to vapcell's website, looked at their charts and
| specifications. I disagree with your assessment.
|
| They specify 3800mAh minimum discharge at 0.2C for their
| 4000mAh cell. They don't show a discharge curve at 0.2C in
| their charts (would be 0.8A) but they do have a 1A discharge.
| When the 1A discharge curve reaches 3V, the energy discharged
| is right around 3800mAh.
|
| Lumafield discharged at 0.2C, and they saw only 3055mAh.
|
| Vapcell's site mostly shows high current discharge curves,
| where yes there is more capacity below 3V available, but with
| Li-ion at lower currents, the curve is very steep past 3V, not
| much more capacity left after that. And when you're discharging
| at high current you won't expect to get the full capacity,
| anyway.
|
| I'll also take this time to point out lygte-info which is a
| treasure trove of battery tests.
|
| [0] https://www.vapcelltech.com/h-pd-193.html
|
| [1] https://www.lygte-info.dk/
| quickthrowman wrote:
| How do you even drain a 3.7V lithium ion battery below 3.3V? My
| devices that use 18650s will not let them go below that. Is it
| 3.3V nominal and the actual voltage is lower, like how they're
| 4.2V fully charged?
| joecool1029 wrote:
| I guess leave them sitting in a laptop in a barn for a few
| years. I was given some old shit gateway the other day, tried
| to charge it, no dice. Ripped the pack apart to find samsung
| 18650's with approx 0.7V voltage.
|
| Against ALL recommendations I put these cells into a MC3000
| and they charged up just fine to 4.2V. It does a 0.15A charge
| per cell until it gets above 3V. Then I had it set to 1.92A
| bulk charge. Fire extinguisher nearby lol
| oulipo2 wrote:
| After we monitored many battery fires, we decided to build a
| casing which can sustain lithium fires for typical e-bike
| batteries: https://www.youtube.com/watch?v=v0NXXfCA2CY
| djmips wrote:
| That's a great idea. Are you making a product or sharing the
| build?
| kragen wrote:
| I think you mean "contain". Very nice.
| jeffbee wrote:
| Neat. How do bikes that have the battery entirely inside the
| metal downtube compare?
|
| Edited: Now that I looked at your product I have low
| expectations for an unbiased answer :-|
| avar wrote:
| Your site (if this is your YouTube video) indicates Bosch
| compatibility with gen 2 motors[A]. I'm curious as to:
|
| 1. It says "Protocol implemented = no", but "Powers bike =
| yes", you can power a Bosch gen 2 motor without implementing
| the protocol, presumably this is referring to the CAN wire on
| the battery.
|
| 2. Your battery kit is 316 EUR without cells, and your BMS
| spare part is 99 EUR. If you can talk to Bosch motors then
| presumably this is where that special sauce is.
|
| I for one might be interested in _just_ something that serves
| to talk with the Bosch motor, and allows one to provide any
| arbitrary 36v source, do you or anyone else make /sell such a
| thing?
|
| E.g. for range extending a cargo bike I'd find the cost/weight
| ratio of a beefy ~1220 Wh AGM 12v car battery coupled with a
| boost converter much more appealing than something that
| emulates the form factor of a ~500 Wh Bosch battery with Li-Ion
| 18650 cells, the range more than makes up for the extra weight.
|
| A. https://infinite-battery.com/pages/compatibility-guide-of-
| th...
| amelius wrote:
| Maybe complement that with a CT-scan of your batteries and AI
| to detect defects.
| jacquesm wrote:
| FLIR monitoring + Ri measurement is a much better predictor
| than a CT scan, especially because you're not going to do
| that continuously.
| jeffbee wrote:
| I just got a new tenant in my rental house and this time I had to
| add a clause to the lease enumerating brands of lithium-ion
| batteries the tenant is allowed to keep on the premises. These
| things are basically grenades that you can buy for $2 on Temu.
| Stronger regulations needed.
| ReptileMan wrote:
| Won't help much. Way too much cheap lithium ion crap with
| incapsulated batteries is flooding the markets
| jeffbee wrote:
| It does help. It raise the opportunity to discuss it, which
| is helpful because not everyone is aware that this is a
| problem, and like many other lease clauses it is there to
| assign blame in case an exceptionally bad event comes to
| pass.
| dylan604 wrote:
| Nah, tenants will sign just to move in, and forget about
| this clause. Just like any tenant that smokes weed
| disregards no drug clauses. Tenants are going to do what
| tenants do. Unless you're doing routine walk throughs
| looking at every single thing in the place that could use a
| battery, then you'll never know. It's a useless
| "regulation", and we have plenty of those in the world
| already.
| jeffbee wrote:
| It's wrong to have an unjustified low opinions of tenants
| as a class. They are normal, well-meaning, intelligent
| people like any other.
| quesera wrote:
| s/tenants/humans/g
|
| The large majority of tenants do not read their lease
| paperwork carefully enough for this clause to make a
| difference.
|
| A large majority of humans don't read EULAs.
|
| A lease clause is useless for liability, because your
| landlord's insurance won't be able to shake down the
| tenant anyway.
|
| Someday soon enough, your insurance might _require_ a
| clause like that. It will still be ignored by tenants
| though.
| trebligdivad wrote:
| It's got to be tricky for people to know what cells they
| have inside their {phone, toothbrush, bike etc}.
| jacquesm wrote:
| Yes, especially wearables and toys. Those are a real problem.
| One of my kids was gifted a toy that had an embedded Lithium
| Ion pouch battery of spectacularly bad quality, the pouch had
| already inflated to the point that it was unsafe to dispose
| of when he got it. I ended up hand delivering the whole thing
| to the local disposal site where they have the proper gear to
| deal with these.
| DenisM wrote:
| The conclusion I drew from this is that if real capacity is much
| less than advertised the battery is best avoided.
| jacquesm wrote:
| Your best predictor of cell failure is brand + where you sourced
| it. Good brand cells sourced through a reliable channel are
| pretty much impossible to get a failure out of without gross
| abuse of the cells.
|
| But far more dangerous than single cell failure is pack failure
| and there the quality of the welding and the balance wires is
| probably a much bigger factor than bad quality cells. You can
| easily create a nice looking bomb from grade A cells, and even
| manufacturers with good name recognition will mess this up from
| time to time.
|
| So buy packs made with quality cells and ensure that whoever
| makes the pack has proper welding gear and QA in place to avoid
| surprises. Never ever use cells without a BMS unless they are in
| a 1S configuration.
| josephg wrote:
| > So buy packs made with quality cells and ensure that whoever
| makes the pack has proper welding gear and QA in place to avoid
| surprises. Never ever use cells without a BMS unless they are
| in a 1S configuration.
|
| How do you put that advice into action? When I'm in an
| electronics store, they don't typically let you look at the
| welds inside each battery bank. (And if they did, I have no
| idea what I'd be looking out for.)
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(page generated 2025-09-26 23:00 UTC)